Activity的onAttachedToWindow和onDetachedFromWindow调用时机源码解析

素颜马尾好姑娘i 2022-05-23 09:48 279阅读 0赞

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先上测试代码：

MyView.java

**\[java\]** view plain copy

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1.  import android.content.Context;  
2.  import android.util.AttributeSet;  
3.  import android.util.Log;  
4.  import android.widget.TextView;  
5.    
6.  public class MyView extends TextView \{  
7.      public MyView(Context context) \{  
8.          super(context);  
9.      \}  
10.   
11.     public MyView(Context context, AttributeSet attrs) \{  
12.         super(context, attrs);  
13.         Log.e(”test”,“view constructor”);  
14.     \}  
15.   
16.     @Override  
17.     protected void onAttachedToWindow() \{  
18.         super.onAttachedToWindow();  
19.         Log.e(”test”, “onAttachedToWindow”);  
20.     \}  
21.   
22.     @Override  
23.     protected void onDetachedFromWindow() \{  
24.         super.onDetachedFromWindow();  
25.         Log.e(”test”, “onDetachedFromWindow”);  
26.     \}  
27. \}

import android.content.Context;
    import android.util.AttributeSet;
    import android.util.Log;
    import android.widget.TextView;
    
    public class MyView extends TextView {
        public MyView(Context context) {
            super(context);
        }
    
        public MyView(Context context, AttributeSet attrs) {
            super(context, attrs);
            Log.e("test","view constructor");
        }
    
        @Override
        protected void onAttachedToWindow() {
            super.onAttachedToWindow();
            Log.e("test", "onAttachedToWindow");
        }
    
        @Override
        protected void onDetachedFromWindow() {
            super.onDetachedFromWindow();
            Log.e("test", "onDetachedFromWindow");
        }
    }

MainActivity.java

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1.  import android.support.v7.app.AppCompatActivity;  
2.  import android.os.Bundle;  
3.  import android.util.Log;  
4.    
5.  public class MainActivity extends AppCompatActivity \{  
6.    
7.      @Override  
8.      protected void onCreate(Bundle savedInstanceState) \{  
9.          super.onCreate(savedInstanceState);  
10.         Log.e(”test”, “before setContextView”);  
11.         setContentView(R.layout.activity\_main);  
12.         Log.e(”test”, “after setContextView”);  
13.     \}  
14.   
15.     @Override  
16.     protected void onResume() \{  
17.         super.onResume();  
18.         Log.e(”test”, “onResume”);  
19.     \}  
20.   
21.     @Override  
22.     protected void onDestroy() \{  
23.         super.onDestroy();  
24.         Log.e(”test”, “onDestroy”);  
25.     \}  
26. \}

import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Log;
    
    public class MainActivity extends AppCompatActivity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Log.e("test", "before setContextView");
            setContentView(R.layout.activity_main);
            Log.e("test", "after setContextView");
        }
    
        @Override
        protected void onResume() {
            super.onResume();
            Log.e("test", "onResume");
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
            Log.e("test", "onDestroy");
        }
    }

运行后输出的Log如下：

![Image 1][]![Image 1][]![运行Log][Log]  
点击返回键退出后，输出的Log如下：

![退出后输出的Log][Log 1]

根据Log的onAttachedToWindow和onDetachedFromWindow的输出情况一目了然。

下面通过源码分析下，他两的调用时机到底在哪。

首先看下onAttachedToWindow的调用时机，在Android源码中onResume调用前会先调用了ActivityThread中的handleResumeActivity，下面是相应的代码：

ActivityThread.java

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1.  final void handleResumeActivity(IBinder token,  
2.              boolean clearHide, boolean isForward, boolean reallyResume) \{  
3.          // If we are getting ready to gc after going to the background, well  
4.          // we are back active so skip it.  
5.          unscheduleGcIdler();  
6.          mSomeActivitiesChanged = true;  
7.    
8.          // TODO Push resumeArgs into the activity for consideration  
9.          ActivityClientRecord r = performResumeActivity(token, clearHide);  
10.   
11.         if (r != null) \{  
12.             final Activity a = r.activity;  
13.   
14.             if (localLOGV) Slog.v(  
15.                 TAG, ”Resume ” + r + “ started activity: ” +  
16.                 a.mStartedActivity + ”, hideForNow: ” + r.hideForNow  
17.                 + ”, finished: ” + a.mFinished);  
18.   
19.             final int forwardBit = isForward ?  
20.                     WindowManager.LayoutParams.SOFT\_INPUT\_IS\_FORWARD\_NAVIGATION : 0;  
21.   
22.             // If the window hasn’t yet been added to the window manager,  
23.             // and this guy didn’t finish itself or start another activity,  
24.             // then go ahead and add the window.  
25.             boolean willBeVisible = !a.mStartedActivity;  
26.             if (!willBeVisible) \{  
27.                 try \{  
28.                     willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(  
29.                             a.getActivityToken());  
30.                 \} catch (RemoteException e) \{  
31.                 \}  
32.             \}  
33.             if (r.window == null && !a.mFinished && willBeVisible) \{  
34.                 r.window = r.activity.getWindow();  
35.                 View decor = r.window.getDecorView();  
36.                 decor.setVisibility(View.INVISIBLE);  
37.                 ViewManager wm = a.getWindowManager();  
38.                 WindowManager.LayoutParams l = r.window.getAttributes();  
39.                 a.mDecor = decor;  
40.                 l.type = WindowManager.LayoutParams.TYPE\_BASE\_APPLICATION;  
41.                 l.softInputMode |= forwardBit;  
42.                 if (a.mVisibleFromClient) \{  
43.                     a.mWindowAdded = true;  
44.                     wm.addView(decor, l);//这里调用了ViewManager中的addView方法。  
45.                 \}  
46.   
47.             // If the window has already been added, but during resume  
48.             // we started another activity, then don’t yet make the  
49.             // window visible.  
50.             \} else if (!willBeVisible) \{  
51.                 if (localLOGV) Slog.v(  
52.                     TAG, ”Launch ” + r + “ mStartedActivity set”);  
53.                 r.hideForNow = true;  
54.             \}  
55.   
56.             // Get rid of anything left hanging around.  
57.             cleanUpPendingRemoveWindows(r);  
58.   
59.             // The window is now visible if it has been added, we are not  
60.             // simply finishing, and we are not starting another activity.  
61.             if (!r.activity.mFinished && willBeVisible  
62.                     && r.activity.mDecor != null && !r.hideForNow) \{  
63.                 if (r.newConfig != null) \{  
64.                     r.tmpConfig.setTo(r.newConfig);  
65.                     if (r.overrideConfig != null) \{  
66.                         r.tmpConfig.updateFrom(r.overrideConfig);  
67.                     \}  
68.                     if (DEBUG\_CONFIGURATION) Slog.v(TAG, “Resuming activity ”  
69.                             + r.activityInfo.name + ” with newConfig ” + r.tmpConfig);  
70.                     performConfigurationChanged(r.activity, r.tmpConfig);  
71.                     freeTextLayoutCachesIfNeeded(r.activity.mCurrentConfig.diff(r.tmpConfig));  
72.                     r.newConfig = null;  
73.                 \}  
74.                 if (localLOGV) Slog.v(TAG, “Resuming ” + r + “ with isForward=”  
75.                         + isForward);  
76.                 WindowManager.LayoutParams l = r.window.getAttributes();  
77.                 if ((l.softInputMode  
78.                         & WindowManager.LayoutParams.SOFT\_INPUT\_IS\_FORWARD\_NAVIGATION)  
79.                         != forwardBit) \{  
80.                     l.softInputMode = (l.softInputMode  
81.                             & (~WindowManager.LayoutParams.SOFT\_INPUT\_IS\_FORWARD\_NAVIGATION))  
82.                             | forwardBit;  
83.                     if (r.activity.mVisibleFromClient) \{  
84.                         ViewManager wm = a.getWindowManager();  
85.                         View decor = r.window.getDecorView();  
86.                         wm.updateViewLayout(decor, l);  
87.                     \}  
88.                 \}  
89.                 r.activity.mVisibleFromServer = true;  
90.                 mNumVisibleActivities++;  
91.                 if (r.activity.mVisibleFromClient) \{  
92.                     r.activity.makeVisible();  
93.                 \}  
94.             \}  
95.             ….  
96.     \}

final void handleResumeActivity(IBinder token,
                boolean clearHide, boolean isForward, boolean reallyResume) {
            // If we are getting ready to gc after going to the background, well
            // we are back active so skip it.
            unscheduleGcIdler();
            mSomeActivitiesChanged = true;
    
            // TODO Push resumeArgs into the activity for consideration
            ActivityClientRecord r = performResumeActivity(token, clearHide);
    
            if (r != null) {
                final Activity a = r.activity;
    
                if (localLOGV) Slog.v(
                    TAG, "Resume " + r + " started activity: " +
                    a.mStartedActivity + ", hideForNow: " + r.hideForNow
                    + ", finished: " + a.mFinished);
    
                final int forwardBit = isForward ?
                        WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;
    
                // If the window hasn't yet been added to the window manager,
                // and this guy didn't finish itself or start another activity,
                // then go ahead and add the window.
                boolean willBeVisible = !a.mStartedActivity;
                if (!willBeVisible) {
                    try {
                        willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(
                                a.getActivityToken());
                    } catch (RemoteException e) {
                    }
                }
                if (r.window == null && !a.mFinished && willBeVisible) {
                    r.window = r.activity.getWindow();
                    View decor = r.window.getDecorView();
                    decor.setVisibility(View.INVISIBLE);
                    ViewManager wm = a.getWindowManager();
                    WindowManager.LayoutParams l = r.window.getAttributes();
                    a.mDecor = decor;
                    l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
                    l.softInputMode |= forwardBit;
                    if (a.mVisibleFromClient) {
                        a.mWindowAdded = true;
                        wm.addView(decor, l);//这里调用了ViewManager中的addView方法。
                    }
    
                // If the window has already been added, but during resume
                // we started another activity, then don't yet make the
                // window visible.
                } else if (!willBeVisible) {
                    if (localLOGV) Slog.v(
                        TAG, "Launch " + r + " mStartedActivity set");
                    r.hideForNow = true;
                }
    
                // Get rid of anything left hanging around.
                cleanUpPendingRemoveWindows(r);
    
                // The window is now visible if it has been added, we are not
                // simply finishing, and we are not starting another activity.
                if (!r.activity.mFinished && willBeVisible
                        && r.activity.mDecor != null && !r.hideForNow) {
                    if (r.newConfig != null) {
                        r.tmpConfig.setTo(r.newConfig);
                        if (r.overrideConfig != null) {
                            r.tmpConfig.updateFrom(r.overrideConfig);
                        }
                        if (DEBUG_CONFIGURATION) Slog.v(TAG, "Resuming activity "
                                + r.activityInfo.name + " with newConfig " + r.tmpConfig);
                        performConfigurationChanged(r.activity, r.tmpConfig);
                        freeTextLayoutCachesIfNeeded(r.activity.mCurrentConfig.diff(r.tmpConfig));
                        r.newConfig = null;
                    }
                    if (localLOGV) Slog.v(TAG, "Resuming " + r + " with isForward="
                            + isForward);
                    WindowManager.LayoutParams l = r.window.getAttributes();
                    if ((l.softInputMode
                            & WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION)
                            != forwardBit) {
                        l.softInputMode = (l.softInputMode
                                & (~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION))
                                | forwardBit;
                        if (r.activity.mVisibleFromClient) {
                            ViewManager wm = a.getWindowManager();
                            View decor = r.window.getDecorView();
                            wm.updateViewLayout(decor, l);
                        }
                    }
                    r.activity.mVisibleFromServer = true;
                    mNumVisibleActivities++;
                    if (r.activity.mVisibleFromClient) {
                        r.activity.makeVisible();
                    }
                }
                ....
        }

看代码中的wm.addView(devor,l);通过该方法将View添加到Window当中（在当前Window也就是Activity，不过Window也可以是Dialog或Toast），而wm是ViewManager类型的，查看对应代码是：

**\[java\]** view plain copy

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1. package android.view;  
2.   
3. /\*\* Interface to let you add and remove child views to an Activity. To get an instance 
4.   \* of this class, call \{@link android.content.Context\#getSystemService(java.lang.String) Context.getSystemService()\}. 
5.   \*/  
6. public interface ViewManager  
7. \{  
8.     /\*\* 
9.      \* Assign the passed LayoutParams to the passed View and add the view to the window. 
10.      \* Throws \{@link android.view.WindowManager.BadTokenException\} for certain programming 
11.      \* errors, such as adding a second view to a window without removing the first view. 
12.      \* Throws \{@link android.view.WindowManager.InvalidDisplayException\} if the window is on a 
13.      \* secondary \{@link Display\} and the specified display can’t be found 
14.      \* (see \{@link android.app.Presentation\}). 
15.      \* @param view The view to be added to this window. 
16.      \* @param params The LayoutParams to assign to view. 
17.      \*/  
18.     public void addView(View view, ViewGroup.LayoutParams params);  
19.     public void updateViewLayout(View view, ViewGroup.LayoutParams params);  
20.     public void removeView(View view);  
21. \}

package android.view;
 
 /** Interface to let you add and remove child views to an Activity. To get an instance
 * of this class, call {@link android.content.Context#getSystemService(java.lang.String) Context.getSystemService()}.
 */
 public interface ViewManager
 {
 /**
 * Assign the passed LayoutParams to the passed View and add the view to the window.
 * Throws {@link android.view.WindowManager.BadTokenException} for certain programming
 * errors, such as adding a second view to a window without removing the first view.
 * Throws {@link android.view.WindowManager.InvalidDisplayException} if the window is on a
 * secondary {@link Display} and the specified display can't be found
 * (see {@link android.app.Presentation}).
 * @param view The view to be added to this window.
 * @param params The LayoutParams to assign to view.
 */
 public void addView(View view, ViewGroup.LayoutParams params);
 public void updateViewLayout(View view, ViewGroup.LayoutParams params);
 public void removeView(View view);
 }

该类是一个接口，在他下面还有一个WindowManager继承于ViewManager，而真正的实现代码在WindowManagerImpl类中，代码如下：

WindowManagerImpl.java

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1.  /\* 
2.  \* @see WindowManager 
3.  \* @see WindowManagerGlobal 
4.  \* @hide 
5.  \*/  
6.  ublic final class WindowManagerImpl implements WindowManager \{  
7.     private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();  
8.     private final Display mDisplay;  
9.     private final Window mParentWindow;  
10.   
11.    private IBinder mDefaultToken;  
12.   
13.    public WindowManagerImpl(Display display) \{  
14.        this(display, null);  
15.    \}  
16.   
17.    private WindowManagerImpl(Display display, Window parentWindow) \{  
18.        mDisplay = display;  
19.        mParentWindow = parentWindow;  
20.    \}  
21.   
22.    public WindowManagerImpl createLocalWindowManager(Window parentWindow) \{  
23.        return new WindowManagerImpl(mDisplay, parentWindow);  
24.    \}  
25.   
26.    public WindowManagerImpl createPresentationWindowManager(Display display) \{  
27.        return new WindowManagerImpl(display, mParentWindow);  
28.    \}  
29.   
30.    /\*\* 
31.     \* Sets the window token to assign when none is specified by the client or 
32.     \* available from the parent window. 
33.     \* 
34.     \* @param token The default token to assign. 
35.     \*/  
36.    public void setDefaultToken(IBinder token) \{  
37.        mDefaultToken = token;  
38.    \}  
39.   
40.    @Override  
41.    public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) \{  
42.        applyDefaultToken(params);  
43.        mGlobal.addView(view, params, mDisplay, mParentWindow);  
44.    \}  
45.   
46.    @Override  
47.    public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) \{  
48.        applyDefaultToken(params);  
49.        mGlobal.updateViewLayout(view, params);  
50.    \}  
51.   
52.    private void applyDefaultToken(@NonNull ViewGroup.LayoutParams params) \{  
53.        // Only use the default token if we don’t have a parent window.  
54.        if (mDefaultToken != null && mParentWindow == null) \{  
55.            if (!(params instanceof WindowManager.LayoutParams)) \{  
56.                throw new IllegalArgumentException(“Params must be WindowManager.LayoutParams”);  
57.            \}  
58.   
59.            // Only use the default token if we don’t already have a token.  
60.            final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;  
61.            if (wparams.token == null) \{  
62.                wparams.token = mDefaultToken;  
63.            \}  
64.        \}  
65.    \}  
66.   
67.    @Override  
68.    public void removeView(View view) \{  
69.        mGlobal.removeView(view, false);  
70.    \}  
71.   
72.    @Override  
73.    public void removeViewImmediate(View view) \{  
74.        mGlobal.removeView(view, true);  
75.    \}  
76.   
77.    @Override  
78.    public Display getDefaultDisplay() \{  
79.        return mDisplay;  
80.    \}

/*
     * @see WindowManager
     * @see WindowManagerGlobal
     * @hide
     */
    public final class WindowManagerImpl implements WindowManager {
        private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
        private final Display mDisplay;
        private final Window mParentWindow;
    
        private IBinder mDefaultToken;
    
        public WindowManagerImpl(Display display) {
            this(display, null);
        }
    
        private WindowManagerImpl(Display display, Window parentWindow) {
            mDisplay = display;
            mParentWindow = parentWindow;
        }
    
        public WindowManagerImpl createLocalWindowManager(Window parentWindow) {
            return new WindowManagerImpl(mDisplay, parentWindow);
        }
    
        public WindowManagerImpl createPresentationWindowManager(Display display) {
            return new WindowManagerImpl(display, mParentWindow);
        }
    
        /**
         * Sets the window token to assign when none is specified by the client or
         * available from the parent window.
         *
         * @param token The default token to assign.
         */
        public void setDefaultToken(IBinder token) {
            mDefaultToken = token;
        }
    
        @Override
        public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
            applyDefaultToken(params);
            mGlobal.addView(view, params, mDisplay, mParentWindow);
        }
    
        @Override
        public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
            applyDefaultToken(params);
            mGlobal.updateViewLayout(view, params);
        }
    
        private void applyDefaultToken(@NonNull ViewGroup.LayoutParams params) {
            // Only use the default token if we don't have a parent window.
            if (mDefaultToken != null && mParentWindow == null) {
                if (!(params instanceof WindowManager.LayoutParams)) {
                    throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
                }
    
                // Only use the default token if we don't already have a token.
                final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
                if (wparams.token == null) {
                    wparams.token = mDefaultToken;
                }
            }
        }
    
        @Override
        public void removeView(View view) {
            mGlobal.removeView(view, false);
        }
    
        @Override
        public void removeViewImmediate(View view) {
            mGlobal.removeView(view, true);
        }
    
        @Override
        public Display getDefaultDisplay() {
            return mDisplay;
        }
    }

**\[java\]** view plain copy

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`从中可以看到addView又调用了 WindowManagerGlobal.java类中的addView，下面看看WindowManagerGlobal.java类的源码：`

`WindowManagerGlobal.java`

`[java] view plain copy print?`

1. `public void addView(View view, ViewGroup.LayoutParams params,  `
2. `        Display display, Window parentWindow) {  `
3. `    if (view == null) {  `
4. `        throw new IllegalArgumentException(“view must not be null”);  `
5. `    }  `
6. `    if (display == null) {  `
7. `        throw new IllegalArgumentException(“display must not be null”);  `
8. `    }  `
9. `    if (!(params instanceof WindowManager.LayoutParams)) {  `
10. `        throw new IllegalArgumentException(“Params must be WindowManager.LayoutParams”);  `
11. `    }  `
12. `  `
13. `    final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;  `
14. `    if (parentWindow != null) {  `
15. `        parentWindow.adjustLayoutParamsForSubWindow(wparams);  `
16. `    } else {  `
17. `        // If there’s no parent, then hardware acceleration for this view is  `
18. `        // set from the application’s hardware acceleration setting.  `
19. `        final Context context = view.getContext();  `
20. `        if (context != null  `
21. `                && (context.getApplicationInfo().flags  `
22. `                        & ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {  `
23. `            wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;  `
24. `        }  `
25. `    }  `
26. `  `
27. `    ViewRootImpl root;  `
28. `    View panelParentView = null;  `
29. `  `
30. `    synchronized (mLock) {  `
31. `        // Start watching for system property changes.  `
32. `        if (mSystemPropertyUpdater == null) {  `
33. `            mSystemPropertyUpdater = new Runnable() {  `
34. `                @Override public void run() {  `
35. `                    synchronized (mLock) {  `
36. `                        for (int i = mRoots.size() - 1; i >= 0; –i) {  `
37. `                            mRoots.get(i).loadSystemProperties();  `
38. `                        }  `
39. `                    }  `
40. `                }  `
41. `            };  `
42. `            SystemProperties.addChangeCallback(mSystemPropertyUpdater);  `
43. `        }  `
44. `  `
45. `        int index = findViewLocked(view, false);  `
46. `        if (index >= 0) {  `
47. `            if (mDyingViews.contains(view)) {  `
48. `                // Don’t wait for MSG_DIE to make it’s way through root’s queue.  `
49. `                mRoots.get(index).doDie();  `
50. `            } else {  `
51. `                throw new IllegalStateException(“View ” + view  `
52. `                        + ” has already been added to the window manager.”);  `
53. `            }  `
54. `            // The previous removeView() had not completed executing. Now it has.  `
55. `        }  `
56. `  `
57. `        // If this is a panel window, then find the window it is being  `
58. `        // attached to for future reference.  `
59. `        if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&  `
60. `                wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {  `
61. `            final int count = mViews.size();  `
62. `            for (int i = 0; i < count; i++) {  `
63. `                if (mRoots.get(i).mWindow.asBinder() == wparams.token) {  `
64. `                    panelParentView = mViews.get(i);  `
65. `                }  `
66. `            }  `
67. `        }  `
68. `  `
69. `        root = new ViewRootImpl(view.getContext(), display);  `
70. `  `
71. `        view.setLayoutParams(wparams);  `
72. `  `
73. `        mViews.add(view);  `
74. `        mRoots.add(root);  `
75. `        mParams.add(wparams);  `
76. `    }  `
77. `  `
78. `    // do this last because it fires off messages to start doing things  `
79. `    try {  `
80. `        root.setView(view, wparams, panelParentView);//这里调用ViewRootImpl类中的setView方法，在该方法中触发了<span style=”color:rgb(101,123,131);font-family:Menlo, Monaco, Consolas, ‘Courier New’, monospace;line-height:20.4px;white-space:pre-wrap;background-color:rgb(246,246,246);”>ViewRootImpl.performTraversals()  `
81. `    } catch (RuntimeException e) {  `
82. `        // BadTokenException or InvalidDisplayException, clean up.  `
83. `        synchronized (mLock) {  `
84. `            final int index = findViewLocked(view, false);  `
85. `            if (index >= 0) {  `
86. `                removeViewLocked(index, true);  `
87. `            }  `
88. `        }  `
89. `        throw e;  `
90. `    }  `
91. `}  `

public void addView(View view, ViewGroup.LayoutParams params,
 Display display, Window parentWindow) {
 if (view == null) {
 throw new IllegalArgumentException("view must not be null");
 }
 if (display == null) {
 throw new IllegalArgumentException("display must not be null");
 }
 if (!(params instanceof WindowManager.LayoutParams)) {
 throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
 }
 
 final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
 if (parentWindow != null) {
 parentWindow.adjustLayoutParamsForSubWindow(wparams);
 } else {
 // If there's no parent, then hardware acceleration for this view is
 // set from the application's hardware acceleration setting.
 final Context context = view.getContext();
 if (context != null
 && (context.getApplicationInfo().flags
 & ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
 wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
 }
 }
 
 ViewRootImpl root;
 View panelParentView = null;
 
 synchronized (mLock) {
 // Start watching for system property changes.
 if (mSystemPropertyUpdater == null) {
 mSystemPropertyUpdater = new Runnable() {
 @Override public void run() {
 synchronized (mLock) {
 for (int i = mRoots.size() - 1; i >= 0; --i) {
 mRoots.get(i).loadSystemProperties();
 }
 }
 }
 };
 SystemProperties.addChangeCallback(mSystemPropertyUpdater);
 }
 
 int index = findViewLocked(view, false);
 if (index >= 0) {
 if (mDyingViews.contains(view)) {
 // Don't wait for MSG_DIE to make it's way through root's queue.
 mRoots.get(index).doDie();
 } else {
 throw new IllegalStateException("View " + view
 + " has already been added to the window manager.");
 }
 // The previous removeView() had not completed executing. Now it has.
 }
 
 // If this is a panel window, then find the window it is being
 // attached to for future reference.
 if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&
 wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {
 final int count = mViews.size();
 for (int i = 0; i < count; i++) {
 if (mRoots.get(i).mWindow.asBinder() == wparams.token) {
 panelParentView = mViews.get(i);
 }
 }
 }
 
 root = new ViewRootImpl(view.getContext(), display);
 
 view.setLayoutParams(wparams);
 
 mViews.add(view);
 mRoots.add(root);
 mParams.add(wparams);
 }
 
 // do this last because it fires off messages to start doing things
 try {
 root.setView(view, wparams, panelParentView);//这里调用ViewRootImpl类中的setView方法，在该方法中触发了ViewRootImpl.performTraversals()
 } catch (RuntimeException e) {
 // BadTokenException or InvalidDisplayException, clean up.
 synchronized (mLock) {
 final int index = findViewLocked(view, false);
 if (index >= 0) {
 removeViewLocked(index, true);
 }
 }
 throw e;
 }
 }

在该方法中的root.setView(view,wparams,panelParentView)方法，调用的是ViewRootImpl类中的setView方法，正是该setView方法触发了ViewRootImpl.performTraversals()方法，也就是View绘制的起点，之后会进行measure,layout,draw三个步骤从而完成一个View的显示工作。

ViewRootImpl.java

**\[java\]** view plain copy

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1.  /\*\* 
2.   \* We have one child 
3.   \*/  
4.  public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) \{  
5.      synchronized (this) \{  
6.          if (mView == null) \{  
7.              mView = view;  
8.    
9.              mAttachInfo.mDisplayState = mDisplay.getState();  
10.             mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);  
11.   
12.             …  
13.             mSoftInputMode = attrs.softInputMode;  
14.             mWindowAttributesChanged = true;  
15.             mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING\_CHANGED;  
16.             mAttachInfo.mRootView = view;  
17.             mAttachInfo.mScalingRequired = mTranslator != null;  
18.             mAttachInfo.mApplicationScale =  
19.                     mTranslator == null ? 1.0f : mTranslator.applicationScale;  
20.             if (panelParentView != null) \{  
21.                 mAttachInfo.mPanelParentWindowToken  
22.                         = panelParentView.getApplicationWindowToken();  
23.             \}  
24.             mAdded = true;  
25.             int res; /\* = WindowManagerImpl.ADD\_OKAY; \*/  
26.   
27.             // Schedule the first layout -before- adding to the window  
28.             // manager, to make sure we do the relayout before receiving  
29.             // any other events from the system.  
30.             requestLayout();//这里开始请求view的绘制  
31.             if ((mWindowAttributes.inputFeatures  
32.                     & WindowManager.LayoutParams.INPUT\_FEATURE\_NO\_INPUT\_CHANNEL) == 0) \{  
33.                 mInputChannel = new InputChannel();  
34.             \}  
35.             try \{  
36.                 mOrigWindowType = mWindowAttributes.type;  
37.                 mAttachInfo.mRecomputeGlobalAttributes = true;  
38.                 collectViewAttributes();  
39.                 res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,  
40.                         getHostVisibility(), mDisplay.getDisplayId(),  
41.                         mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,  
42.                         mAttachInfo.mOutsets, mInputChannel);  
43.             \} catch (RemoteException e) \{  
44.                 mAdded = false;  
45.                 mView = null;  
46.                 mAttachInfo.mRootView = null;  
47.                 mInputChannel = null;  
48.                 mFallbackEventHandler.setView(null);  
49.                 unscheduleTraversals();  
50.                 setAccessibilityFocus(null, null);  
51.                 throw new RuntimeException(“Adding window failed”, e);  
52.             \} finally \{  
53.                 if (restore) \{  
54.                     attrs.restore();  
55.                 \}  
56.             \}  
57.             ….  
58.         \}  
59.     \}  
60. \}

/**
         * We have one child
         */
        public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
            synchronized (this) {
                if (mView == null) {
                    mView = view;
    
                    mAttachInfo.mDisplayState = mDisplay.getState();
                    mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);
    
                    ...
                    mSoftInputMode = attrs.softInputMode;
                    mWindowAttributesChanged = true;
                    mWindowAttributesChangesFlag = WindowManager.LayoutParams.EVERYTHING_CHANGED;
                    mAttachInfo.mRootView = view;
                    mAttachInfo.mScalingRequired = mTranslator != null;
                    mAttachInfo.mApplicationScale =
                            mTranslator == null ? 1.0f : mTranslator.applicationScale;
                    if (panelParentView != null) {
                        mAttachInfo.mPanelParentWindowToken
                                = panelParentView.getApplicationWindowToken();
                    }
                    mAdded = true;
                    int res; /* = WindowManagerImpl.ADD_OKAY; */
    
                    // Schedule the first layout -before- adding to the window
                    // manager, to make sure we do the relayout before receiving
                    // any other events from the system.
                    requestLayout();//这里开始请求view的绘制
                    if ((mWindowAttributes.inputFeatures
                            & WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
                        mInputChannel = new InputChannel();
                    }
                    try {
                        mOrigWindowType = mWindowAttributes.type;
                        mAttachInfo.mRecomputeGlobalAttributes = true;
                        collectViewAttributes();
                        res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                                getHostVisibility(), mDisplay.getDisplayId(),
                                mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                                mAttachInfo.mOutsets, mInputChannel);
                    } catch (RemoteException e) {
                        mAdded = false;
                        mView = null;
                        mAttachInfo.mRootView = null;
                        mInputChannel = null;
                        mFallbackEventHandler.setView(null);
                        unscheduleTraversals();
                        setAccessibilityFocus(null, null);
                        throw new RuntimeException("Adding window failed", e);
                    } finally {
                        if (restore) {
                            attrs.restore();
                        }
                    }
                    ....
                }
            }
        }

在setView的requestLayout方法中开始View的绘制。

ViewRootImpl.java

**\[java\]** view plain copy

print ?

1.  void scheduleTraversals() \{  
2.      if (!mTraversalScheduled) \{  
3.          mTraversalScheduled = true;  
4.          mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();  
5.          mChoreographer.postCallback(  
6.                  Choreographer.CALLBACK\_TRAVERSAL, mTraversalRunnable, null);  
7.          if (!mUnbufferedInputDispatch) \{  
8.              scheduleConsumeBatchedInput();  
9.          \}  
10.         notifyRendererOfFramePending();  
11.         pokeDrawLockIfNeeded();  
12.     \}  
13. \}  
14.   
15. void scheduleTraversals() \{  
16.     if (!mTraversalScheduled) \{  
17.         mTraversalScheduled = true;  
18.         mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();  
19.         mChoreographer.postCallback(  
20.                 Choreographer.CALLBACK\_TRAVERSAL, mTraversalRunnable, null);  
21.         if (!mUnbufferedInputDispatch) \{  
22.             scheduleConsumeBatchedInput();  
23.         \}  
24.         notifyRendererOfFramePending();  
25.         pokeDrawLockIfNeeded();  
26.     \}  
27. \}  
28. final class TraversalRunnable implements Runnable \{  
29.     @Override  
30.     public void run() \{  
31.         doTraversal();  
32.     \}  
33. \}  
34. final TraversalRunnable mTraversalRunnable = new TraversalRunnable();  
35. void doTraversal() \{  
36.     if (mTraversalScheduled) \{  
37.         mTraversalScheduled = false;  
38.         mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);  
39.   
40.         if (mProfile) \{  
41.             Debug.startMethodTracing(”ViewAncestor”);  
42.         \}  
43.   
44.         performTraversals();  
45.   
46.         if (mProfile) \{  
47.             Debug.stopMethodTracing();  
48.             mProfile = false;  
49.         \}  
50.     \}  
51. \}

void scheduleTraversals() {
            if (!mTraversalScheduled) {
                mTraversalScheduled = true;
                mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
                mChoreographer.postCallback(
                        Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
                if (!mUnbufferedInputDispatch) {
                    scheduleConsumeBatchedInput();
                }
                notifyRendererOfFramePending();
                pokeDrawLockIfNeeded();
            }
        }
    
        void scheduleTraversals() {
            if (!mTraversalScheduled) {
                mTraversalScheduled = true;
                mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
                mChoreographer.postCallback(
                        Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
                if (!mUnbufferedInputDispatch) {
                    scheduleConsumeBatchedInput();
                }
                notifyRendererOfFramePending();
                pokeDrawLockIfNeeded();
            }
        }
        final class TraversalRunnable implements Runnable {
            @Override
            public void run() {
                doTraversal();
            }
        }
        final TraversalRunnable mTraversalRunnable = new TraversalRunnable();
        void doTraversal() {
            if (mTraversalScheduled) {
                mTraversalScheduled = false;
                mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);
    
                if (mProfile) {
                    Debug.startMethodTracing("ViewAncestor");
                }
    
                performTraversals();
    
                if (mProfile) {
                    Debug.stopMethodTracing();
                    mProfile = false;
                }
            }
        }

在scheduleTraversals()方法中向mChoreographer中postCallback，而具体的Runable内容在TraversalRunnable类中，该类在run函数中直接执行doTraversal()方法，可以看到在该方法中最终调用了performTraversals()开启View的绘制工作。

查看ViewRootImpl.java中的performTraversals()的源码如下：

ViewRootImpl.java中的performTraversals()方法

**\[java\]** view plain copy

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1.  private void performTraversals() \{  
2.          // cache mView since it is used so much below…  
3.          final View host = mView;  
4.          …  
5.          if (host == null || !mAdded)  
6.              return;  
7.    
8.          mIsInTraversal = true;  
9.          mWillDrawSoon = true;  
10.         boolean windowSizeMayChange = false;  
11.         boolean newSurface = false;  
12.         boolean surfaceChanged = false;  
13.         WindowManager.LayoutParams lp = mWindowAttributes;  
14.   
15.         int desiredWindowWidth;  
16.         int desiredWindowHeight;  
17.   
18.         final int viewVisibility = getHostVisibility();  
19.         boolean viewVisibilityChanged = mViewVisibility != viewVisibility  
20.                 || mNewSurfaceNeeded;  
21.   
22.         WindowManager.LayoutParams params = null;  
23.         if (mWindowAttributesChanged) \{  
24.             mWindowAttributesChanged = false;  
25.             surfaceChanged = true;  
26.             params = lp;  
27.         \}  
28.         CompatibilityInfo compatibilityInfo = mDisplayAdjustments.getCompatibilityInfo();  
29.         if (compatibilityInfo.supportsScreen() == mLastInCompatMode) \{  
30.             params = lp;  
31.             mFullRedrawNeeded = true;  
32.             mLayoutRequested = true;  
33.             if (mLastInCompatMode) \{  
34.                 params.privateFlags &= ~WindowManager.LayoutParams.PRIVATE\_FLAG\_COMPATIBLE\_WINDOW;  
35.                 mLastInCompatMode = false;  
36.             \} else \{  
37.                 params.privateFlags |= WindowManager.LayoutParams.PRIVATE\_FLAG\_COMPATIBLE\_WINDOW;  
38.                 mLastInCompatMode = true;  
39.             \}  
40.         \}  
41.   
42.         mWindowAttributesChangesFlag = 0;  
43.   
44.         Rect frame = mWinFrame;  
45.         if (mFirst) \{  
46.             mFullRedrawNeeded = true;  
47.             mLayoutRequested = true;  
48.   
49.             if (lp.type == WindowManager.LayoutParams.TYPE\_STATUS\_BAR\_PANEL  
50.                     || lp.type == WindowManager.LayoutParams.TYPE\_INPUT\_METHOD) \{  
51.                 // NOTE – system code, won’t try to do compat mode.  
52.                 Point size = new Point();  
53.                 mDisplay.getRealSize(size);  
54.                 desiredWindowWidth = size.x;  
55.                 desiredWindowHeight = size.y;  
56.             \} else \{  
57.                 DisplayMetrics packageMetrics =  
58.                     mView.getContext().getResources().getDisplayMetrics();  
59.                 desiredWindowWidth = packageMetrics.widthPixels;  
60.                 desiredWindowHeight = packageMetrics.heightPixels;  
61.             \}  
62.   
63.             // We used to use the following condition to choose 32 bits drawing caches:  
64.             // PixelFormat.hasAlpha(lp.format) || lp.format == PixelFormat.RGBX\_8888  
65.             // However, windows are now always 32 bits by default, so choose 32 bits  
66.             mAttachInfo.mUse32BitDrawingCache = true;  
67.             mAttachInfo.mHasWindowFocus = false;  
68.             mAttachInfo.mWindowVisibility = viewVisibility;  
69.             mAttachInfo.mRecomputeGlobalAttributes = false;  
70.             viewVisibilityChanged = false;  
71.             mLastConfiguration.setTo(host.getResources().getConfiguration());  
72.             mLastSystemUiVisibility = mAttachInfo.mSystemUiVisibility;  
73.             // Set the layout direction if it has not been set before (inherit is the default)  
74.             if (mViewLayoutDirectionInitial == View.LAYOUT\_DIRECTION\_INHERIT) \{  
75.                 host.setLayoutDirection(mLastConfiguration.getLayoutDirection());  
76.             \}  
77.             host.dispatchAttachedToWindow(mAttachInfo, 0);//这里调用了View的dispatchAttachedToWindow，也就是这里回调了onAttachedToWindow方法。  
78.             mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(true);  
79.             dispatchApplyInsets(host);  
80.             //Log.i(TAG, “Screen on initialized: ” + attachInfo.mKeepScreenOn);  
81.   
82.         \} else \{  
83.             desiredWindowWidth = frame.width();  
84.             desiredWindowHeight = frame.height();  
85.             if (desiredWindowWidth != mWidth || desiredWindowHeight != mHeight) \{  
86.                 if (DEBUG\_ORIENTATION) Log.v(TAG,  
87.                         ”View ” + host + “ resized to: ” + frame);  
88.                 mFullRedrawNeeded = true;  
89.                 mLayoutRequested = true;  
90.                 windowSizeMayChange = true;  
91.             \}  
92.         \}  
93.   
94.         …  
95.     \}

private void performTraversals() {
            // cache mView since it is used so much below...
            final View host = mView;
            ...
            if (host == null || !mAdded)
                return;
    
            mIsInTraversal = true;
            mWillDrawSoon = true;
            boolean windowSizeMayChange = false;
            boolean newSurface = false;
            boolean surfaceChanged = false;
            WindowManager.LayoutParams lp = mWindowAttributes;
    
            int desiredWindowWidth;
            int desiredWindowHeight;
    
            final int viewVisibility = getHostVisibility();
            boolean viewVisibilityChanged = mViewVisibility != viewVisibility
                    || mNewSurfaceNeeded;
    
            WindowManager.LayoutParams params = null;
            if (mWindowAttributesChanged) {
                mWindowAttributesChanged = false;
                surfaceChanged = true;
                params = lp;
            }
            CompatibilityInfo compatibilityInfo = mDisplayAdjustments.getCompatibilityInfo();
            if (compatibilityInfo.supportsScreen() == mLastInCompatMode) {
                params = lp;
                mFullRedrawNeeded = true;
                mLayoutRequested = true;
                if (mLastInCompatMode) {
                    params.privateFlags &= ~WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
                    mLastInCompatMode = false;
                } else {
                    params.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
                    mLastInCompatMode = true;
                }
            }
    
            mWindowAttributesChangesFlag = 0;
    
            Rect frame = mWinFrame;
            if (mFirst) {
                mFullRedrawNeeded = true;
                mLayoutRequested = true;
    
                if (lp.type == WindowManager.LayoutParams.TYPE_STATUS_BAR_PANEL
                        || lp.type == WindowManager.LayoutParams.TYPE_INPUT_METHOD) {
                    // NOTE -- system code, won't try to do compat mode.
                    Point size = new Point();
                    mDisplay.getRealSize(size);
                    desiredWindowWidth = size.x;
                    desiredWindowHeight = size.y;
                } else {
                    DisplayMetrics packageMetrics =
                        mView.getContext().getResources().getDisplayMetrics();
                    desiredWindowWidth = packageMetrics.widthPixels;
                    desiredWindowHeight = packageMetrics.heightPixels;
                }
    
                // We used to use the following condition to choose 32 bits drawing caches:
                // PixelFormat.hasAlpha(lp.format) || lp.format == PixelFormat.RGBX_8888
                // However, windows are now always 32 bits by default, so choose 32 bits
                mAttachInfo.mUse32BitDrawingCache = true;
                mAttachInfo.mHasWindowFocus = false;
                mAttachInfo.mWindowVisibility = viewVisibility;
                mAttachInfo.mRecomputeGlobalAttributes = false;
                viewVisibilityChanged = false;
                mLastConfiguration.setTo(host.getResources().getConfiguration());
                mLastSystemUiVisibility = mAttachInfo.mSystemUiVisibility;
                // Set the layout direction if it has not been set before (inherit is the default)
                if (mViewLayoutDirectionInitial == View.LAYOUT_DIRECTION_INHERIT) {
                    host.setLayoutDirection(mLastConfiguration.getLayoutDirection());
                }
                host.dispatchAttachedToWindow(mAttachInfo, 0);//这里调用了View的dispatchAttachedToWindow，也就是这里回调了onAttachedToWindow方法。
                mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(true);
                dispatchApplyInsets(host);
                //Log.i(TAG, "Screen on initialized: " + attachInfo.mKeepScreenOn);
    
            } else {
                desiredWindowWidth = frame.width();
                desiredWindowHeight = frame.height();
                if (desiredWindowWidth != mWidth || desiredWindowHeight != mHeight) {
                    if (DEBUG_ORIENTATION) Log.v(TAG,
                            "View " + host + " resized to: " + frame);
                    mFullRedrawNeeded = true;
                    mLayoutRequested = true;
                    windowSizeMayChange = true;
                }
            }
    
            ...
        }

在该方法中调用了host.dispatchAttachedToWindow(mAttachInfo, 0);方法。host是上面传下来的DecodView，该类继承与FrameLayout类，也就是ViewGroup的子类，所以先调用的是ViewGroup中的dispatchAttachedToWindow，其代码如下：

ViewGroup.java

**\[java\]** view plain copy

print ?

1. @Override  
2. void dispatchAttachedToWindow(AttachInfo info, int visibility) \{  
3.     mGroupFlags |= FLAG\_PREVENT\_DISPATCH\_ATTACHED\_TO\_WINDOW;  
4.     super.dispatchAttachedToWindow(info, visibility);//这里先调用父类，也就是View的dispathcAttachedToWindow。  
5.     mGroupFlags &= ~FLAG\_PREVENT\_DISPATCH\_ATTACHED\_TO\_WINDOW;  
6.   
7.     final int count = mChildrenCount;  
8.     final View\[\] children = mChildren;  
9.     for (int i = 0; i < count; i++) \{  
10.         final View child = children\[i\];  
11.         child.dispatchAttachedToWindow(info,  
12.                 combineVisibility(visibility, child.getVisibility()));//这里调用子View的<span style=”font-family:Arial, Helvetica, sans-serif;”>dispatchAttachedToWindow  
13.     \}  
14.     final int transientCount = mTransientIndices == null ? 0 : mTransientIndices.size();  
15.     for (int i = 0; i < transientCount; ++i) \{  
16.         View view = mTransientViews.get(i);  
17.         view.dispatchAttachedToWindow(info,  
18.                 combineVisibility(visibility, view.getVisibility()));  
19.     \}  
20. \}

@Override
 void dispatchAttachedToWindow(AttachInfo info, int visibility) {
 mGroupFlags |= FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW;
 super.dispatchAttachedToWindow(info, visibility);//这里先调用父类，也就是View的dispathcAttachedToWindow。
 mGroupFlags &= ~FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW;
 
 final int count = mChildrenCount;
 final View[] children = mChildren;
 for (int i = 0; i < count; i++) {
 final View child = children[i];
 child.dispatchAttachedToWindow(info,
 combineVisibility(visibility, child.getVisibility()));//这里调用子View的dispatchAttachedToWindow
 }
 final int transientCount = mTransientIndices == null ? 0 : mTransientIndices.size();
 for (int i = 0; i < transientCount; ++i) {
 View view = mTransientViews.get(i);
 view.dispatchAttachedToWindow(info,
 combineVisibility(visibility, view.getVisibility()));
 }
 }

下面查看对应的View类中的dispatchAttacToWindow。代码如下：

View.java

**\[java\]** view plain copy

print ?

1. void dispatchAttachedToWindow(AttachInfo info, int visibility) \{  
2.         //System.out.println(“Attached! ” + this);  
3.         mAttachInfo = info;  
4.         if (mOverlay != null) \{  
5.             mOverlay.getOverlayView().dispatchAttachedToWindow(info, visibility);  
6.         \}  
7.         mWindowAttachCount++;  
8.         // We will need to evaluate the drawable state at least once.  
9.         mPrivateFlags |= PFLAG\_DRAWABLE\_STATE\_DIRTY;  
10.         if (mFloatingTreeObserver != null) \{  
11.             info.mTreeObserver.merge(mFloatingTreeObserver);  
12.             mFloatingTreeObserver = null;  
13.         \}  
14.         if ((mPrivateFlags&PFLAG\_SCROLL\_CONTAINER) != 0) \{  
15.             mAttachInfo.mScrollContainers.add(this);  
16.             mPrivateFlags |= PFLAG\_SCROLL\_CONTAINER\_ADDED;  
17.         \}  
18.         performCollectViewAttributes(mAttachInfo, visibility);  
19.         onAttachedToWindow();//快看，快看，在这里！终于找到这个方法调用的位置了  
20.         ListenerInfo li = mListenerInfo;  
21.         final CopyOnWriteArrayList<OnAttachStateChangeListener> listeners =  
22.                 li != null ? li.mOnAttachStateChangeListeners : null;  
23.         if (listeners != null && listeners.size() > 0) \{  
24.             // NOTE: because of the use of CopyOnWriteArrayList, we \*must\* use an iterator to  
25.             // perform the dispatching. The iterator is a safe guard against listeners that  
26.             // could mutate the list by calling the various add/remove methods. This prevents  
27.             // the array from being modified while we iterate it.  
28.             for (OnAttachStateChangeListener listener : listeners) \{  
29.                 listener.onViewAttachedToWindow(this);//  
30.             \}  
31.         \}  
32.   
33.         int vis = info.mWindowVisibility;  
34.         if (vis != GONE) \{  
35.             onWindowVisibilityChanged(vis);  
36.         \}  
37.   
38.         // Send onVisibilityChanged directly instead of dispatchVisibilityChanged.  
39.         // As all views in the subtree will already receive dispatchAttachedToWindow  
40.         // traversing the subtree again here is not desired.  
41.         onVisibilityChanged(this, visibility);  
42.   
43.         if ((mPrivateFlags&PFLAG\_DRAWABLE\_STATE\_DIRTY) != 0) \{  
44.             // If nobody has evaluated the drawable state yet, then do it now.  
45.             refreshDrawableState();  
46.         \}  
47.         needGlobalAttributesUpdate(false);  
48.     \}

void dispatchAttachedToWindow(AttachInfo info, int visibility) {
 //System.out.println("Attached! " + this);
 mAttachInfo = info;
 if (mOverlay != null) {
 mOverlay.getOverlayView().dispatchAttachedToWindow(info, visibility);
 }
 mWindowAttachCount++;
 // We will need to evaluate the drawable state at least once.
 mPrivateFlags |= PFLAG_DRAWABLE_STATE_DIRTY;
 if (mFloatingTreeObserver != null) {
 info.mTreeObserver.merge(mFloatingTreeObserver);
 mFloatingTreeObserver = null;
 }
 if ((mPrivateFlags&PFLAG_SCROLL_CONTAINER) != 0) {
 mAttachInfo.mScrollContainers.add(this);
 mPrivateFlags |= PFLAG_SCROLL_CONTAINER_ADDED;
 }
 performCollectViewAttributes(mAttachInfo, visibility);
 onAttachedToWindow();//快看，快看，在这里！终于找到这个方法调用的位置了
 ListenerInfo li = mListenerInfo;
 final CopyOnWriteArrayList<OnAttachStateChangeListener> listeners =
 li != null ? li.mOnAttachStateChangeListeners : null;
 if (listeners != null && listeners.size() > 0) {
 // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
 // perform the dispatching. The iterator is a safe guard against listeners that
 // could mutate the list by calling the various add/remove methods. This prevents
 // the array from being modified while we iterate it.
 for (OnAttachStateChangeListener listener : listeners) {
 listener.onViewAttachedToWindow(this);//
 }
 }
 
 int vis = info.mWindowVisibility;
 if (vis != GONE) {
 onWindowVisibilityChanged(vis);
 }
 
 // Send onVisibilityChanged directly instead of dispatchVisibilityChanged.
 // As all views in the subtree will already receive dispatchAttachedToWindow
 // traversing the subtree again here is not desired.
 onVisibilityChanged(this, visibility);
 
 if ((mPrivateFlags&PFLAG_DRAWABLE_STATE_DIRTY) != 0) {
 // If nobody has evaluated the drawable state yet, then do it now.
 refreshDrawableState();
 }
 needGlobalAttributesUpdate(false);
 }

从上面代码可以看出一个布局的onAttachedToWindow会先调用自己的，然后再调用自己孩子的。而且从View.java的代码中也可以看出onAttachedToWindow和View自身的visibility无关，即使visibility==GONE，该方法也会调用。

好，下面来分析下onDetachedFromWindow方法的调用时机。在onDestory调用前会调用ActivityThread.java中的handleDestroyActivity方法，贴出代码：

ActivityThread.java

**\[java\]** view plain copy

print ?

1.  private void handleDestroyActivity(IBinder token, boolean finishing,  
2.          int configChanges, boolean getNonConfigInstance) \{  
3.      ActivityClientRecord r = performDestroyActivity(token, finishing,  
4.              configChanges, getNonConfigInstance);  
5.      if (r != null) \{  
6.          cleanUpPendingRemoveWindows(r);  
7.          WindowManager wm = r.activity.getWindowManager();  
8.          View v = r.activity.mDecor;  
9.          if (v != null) \{  
10.             if (r.activity.mVisibleFromServer) \{  
11.                 mNumVisibleActivities–;  
12.             \}  
13.             IBinder wtoken = v.getWindowToken();  
14.             if (r.activity.mWindowAdded) \{  
15.                 if (r.onlyLocalRequest) \{  
16.                     // Hold off on removing this until the new activity’s  
17.                     // window is being added.  
18.                     r.mPendingRemoveWindow = v;  
19.                     r.mPendingRemoveWindowManager = wm;  
20.                 \} else \{  
21.                     wm.removeViewImmediate(v);//看这里，看这里  
22.                 \}  
23.             \}  
24.             if (wtoken != null && r.mPendingRemoveWindow == null) \{  
25.                 WindowManagerGlobal.getInstance().closeAll(wtoken,  
26.                         r.activity.getClass().getName(), ”Activity”);  
27.             \}  
28.             r.activity.mDecor = null;  
29.         \}  
30.         if (r.mPendingRemoveWindow == null) \{  
31.             // If we are delaying the removal of the activity window, then  
32.             // we can’t clean up all windows here.  Note that we can’t do  
33.             // so later either, which means any windows that aren’t closed  
34.             // by the app will leak.  Well we try to warning them a lot  
35.             // about leaking windows, because that is a bug, so if they are  
36.             // using this recreate facility then they get to live with leaks.  
37.             WindowManagerGlobal.getInstance().closeAll(token,  
38.                     r.activity.getClass().getName(), ”Activity”);  
39.         \}  
40.   
41.         // Mocked out contexts won’t be participating in the normal  
42.         // process lifecycle, but if we’re running with a proper  
43.         // ApplicationContext we need to have it tear down things  
44.         // cleanly.  
45.         Context c = r.activity.getBaseContext();  
46.         if (c instanceof ContextImpl) \{  
47.             ((ContextImpl) c).scheduleFinalCleanup(  
48.                     r.activity.getClass().getName(), ”Activity”);  
49.         \}  
50.     \}  
51.     if (finishing) \{  
52.         try \{  
53.             ActivityManagerNative.getDefault().activityDestroyed(token);  
54.         \} catch (RemoteException ex) \{  
55.             // If the system process has died, it’s game over for everyone.  
56.         \}  
57.     \}  
58.     mSomeActivitiesChanged = true;  
59. \}

private void handleDestroyActivity(IBinder token, boolean finishing,
                int configChanges, boolean getNonConfigInstance) {
            ActivityClientRecord r = performDestroyActivity(token, finishing,
                    configChanges, getNonConfigInstance);
            if (r != null) {
                cleanUpPendingRemoveWindows(r);
                WindowManager wm = r.activity.getWindowManager();
                View v = r.activity.mDecor;
                if (v != null) {
                    if (r.activity.mVisibleFromServer) {
                        mNumVisibleActivities--;
                    }
                    IBinder wtoken = v.getWindowToken();
                    if (r.activity.mWindowAdded) {
                        if (r.onlyLocalRequest) {
                            // Hold off on removing this until the new activity's
                            // window is being added.
                            r.mPendingRemoveWindow = v;
                            r.mPendingRemoveWindowManager = wm;
                        } else {
                            wm.removeViewImmediate(v);//看这里，看这里
                        }
                    }
                    if (wtoken != null && r.mPendingRemoveWindow == null) {
                        WindowManagerGlobal.getInstance().closeAll(wtoken,
                                r.activity.getClass().getName(), "Activity");
                    }
                    r.activity.mDecor = null;
                }
                if (r.mPendingRemoveWindow == null) {
                    // If we are delaying the removal of the activity window, then
                    // we can't clean up all windows here.  Note that we can't do
                    // so later either, which means any windows that aren't closed
                    // by the app will leak.  Well we try to warning them a lot
                    // about leaking windows, because that is a bug, so if they are
                    // using this recreate facility then they get to live with leaks.
                    WindowManagerGlobal.getInstance().closeAll(token,
                            r.activity.getClass().getName(), "Activity");
                }
    
                // Mocked out contexts won't be participating in the normal
                // process lifecycle, but if we're running with a proper
                // ApplicationContext we need to have it tear down things
                // cleanly.
                Context c = r.activity.getBaseContext();
                if (c instanceof ContextImpl) {
                    ((ContextImpl) c).scheduleFinalCleanup(
                            r.activity.getClass().getName(), "Activity");
                }
            }
            if (finishing) {
                try {
                    ActivityManagerNative.getDefault().activityDestroyed(token);
                } catch (RemoteException ex) {
                    // If the system process has died, it's game over for everyone.
                }
            }
            mSomeActivitiesChanged = true;
        }

看代码中的wm.removeViewImmediate方法，还是走到WindowManagerImpl类中的removeViewImmediate，代码如下：

WindowManagerImpl.java

**\[java\]** view plain copy

print ?

1.  @Override  
2.  public void removeViewImmediate(View view) \{  
3.      mGlobal.removeView(view, true);  
4.  \}

@Override
        public void removeViewImmediate(View view) {
            mGlobal.removeView(view, true);
        }

好熟悉啊，还是走到了WindowManagerGlobal类中的removeView，代码如下：  
WindowManagerGlobal.java

**\[java\]** view plain copy

print ?

1.  public void removeView(View view, boolean immediate) \{  
2.      if (view == null) \{  
3.          throw new IllegalArgumentException(“view must not be null”);  
4.      \}  
5.    
6.      synchronized (mLock) \{  
7.          int index = findViewLocked(view, true);  
8.          View curView = mRoots.get(index).getView();  
9.          removeViewLocked(index, immediate);  
10.         if (curView == view) \{  
11.             return;  
12.         \}  
13.   
14.         throw new IllegalStateException(“Calling with view ” + view  
15.                 + ” but the ViewAncestor is attached to ” + curView);  
16.     \}  
17. \}  
18. private void removeViewLocked(int index, boolean immediate) \{  
19.     ViewRootImpl root = mRoots.get(index);  
20.     View view = root.getView();  
21.   
22.     if (view != null) \{  
23.         InputMethodManager imm = InputMethodManager.getInstance();  
24.         if (imm != null) \{  
25.             imm.windowDismissed(mViews.get(index).getWindowToken());  
26.         \}  
27.     \}  
28.     boolean deferred = root.die(immediate);  
29.     if (view != null) \{  
30.         view.assignParent(null);  
31.         if (deferred) \{  
32.             mDyingViews.add(view);  
33.         \}  
34.     \}  
35. \}

public void removeView(View view, boolean immediate) {
            if (view == null) {
                throw new IllegalArgumentException("view must not be null");
            }
    
            synchronized (mLock) {
                int index = findViewLocked(view, true);
                View curView = mRoots.get(index).getView();
                removeViewLocked(index, immediate);
                if (curView == view) {
                    return;
                }
    
                throw new IllegalStateException("Calling with view " + view
                        + " but the ViewAncestor is attached to " + curView);
            }
        }
        private void removeViewLocked(int index, boolean immediate) {
            ViewRootImpl root = mRoots.get(index);
            View view = root.getView();
    
            if (view != null) {
                InputMethodManager imm = InputMethodManager.getInstance();
                if (imm != null) {
                    imm.windowDismissed(mViews.get(index).getWindowToken());
                }
            }
            boolean deferred = root.die(immediate);
            if (view != null) {
                view.assignParent(null);
                if (deferred) {
                    mDyingViews.add(view);
                }
            }
        }

跟着代码继续走，到了ViewRootImpl类中的die，代码如下：

ViewRootImpl.java

**\[java\]** view plain copy

print ?

1.  /\*\* 
2.       \* @param immediate True, do now if not in traversal. False, put on queue and do later. 
3.       \* @return True, request has been queued. False, request has been completed. 
4.       \*/  
5.      boolean die(boolean immediate) \{  
6.          // Make sure we do execute immediately if we are in the middle of a traversal or the damage  
7.          // done by dispatchDetachedFromWindow will cause havoc on return.  
8.          if (immediate && !mIsInTraversal) \{  
9.              doDie();  
10.             return false;  
11.         \}  
12.   
13.         if (!mIsDrawing) \{  
14.             destroyHardwareRenderer();  
15.         \} else \{  
16.             Log.e(TAG, ”Attempting to destroy the window while drawing!\\n” +  
17.                     ”  window=” + this + “, title=” + mWindowAttributes.getTitle());  
18.         \}  
19.         mHandler.sendEmptyMessage(MSG\_DIE);  
20.         return true;  
21.     \}  
22.   
23.     void doDie() \{  
24.         checkThread();  
25.         if (LOCAL\_LOGV) Log.v(TAG, “DIE in ” + this + “ of ” + mSurface);  
26.         synchronized (this) \{  
27.             if (mRemoved) \{  
28.                 return;  
29.             \}  
30.             mRemoved = true;  
31.             if (mAdded) \{  
32.                 dispatchDetachedFromWindow();//看这里，看这里  
33.             \}  
34.   
35.             if (mAdded && !mFirst) \{  
36.                 destroyHardwareRenderer();  
37.   
38.                 if (mView != null) \{  
39.                     int viewVisibility = mView.getVisibility();  
40.                     boolean viewVisibilityChanged = mViewVisibility != viewVisibility;  
41.                     if (mWindowAttributesChanged || viewVisibilityChanged) \{  
42.                         // If layout params have been changed, first give them  
43.                         // to the window manager to make sure it has the correct  
44.                         // animation info.  
45.                         try \{  
46.                             if ((relayoutWindow(mWindowAttributes, viewVisibility, false)  
47.                                     & WindowManagerGlobal.RELAYOUT\_RES\_FIRST\_TIME) != 0) \{  
48.                                 mWindowSession.finishDrawing(mWindow);  
49.                             \}  
50.                         \} catch (RemoteException e) \{  
51.                         \}  
52.                     \}  
53.   
54.                     mSurface.release();  
55.                 \}  
56.             \}  
57.   
58.             mAdded = false;  
59.         \}  
60.         WindowManagerGlobal.getInstance().doRemoveView(this);  
61.     \}

/**
         * @param immediate True, do now if not in traversal. False, put on queue and do later.
         * @return True, request has been queued. False, request has been completed.
         */
        boolean die(boolean immediate) {
            // Make sure we do execute immediately if we are in the middle of a traversal or the damage
            // done by dispatchDetachedFromWindow will cause havoc on return.
            if (immediate && !mIsInTraversal) {
                doDie();
                return false;
            }
    
            if (!mIsDrawing) {
                destroyHardwareRenderer();
            } else {
                Log.e(TAG, "Attempting to destroy the window while drawing!\n" +
                        "  window=" + this + ", title=" + mWindowAttributes.getTitle());
            }
            mHandler.sendEmptyMessage(MSG_DIE);
            return true;
        }
    
        void doDie() {
            checkThread();
            if (LOCAL_LOGV) Log.v(TAG, "DIE in " + this + " of " + mSurface);
            synchronized (this) {
                if (mRemoved) {
                    return;
                }
                mRemoved = true;
                if (mAdded) {
                    dispatchDetachedFromWindow();//看这里，看这里
                }
    
                if (mAdded && !mFirst) {
                    destroyHardwareRenderer();
    
                    if (mView != null) {
                        int viewVisibility = mView.getVisibility();
                        boolean viewVisibilityChanged = mViewVisibility != viewVisibility;
                        if (mWindowAttributesChanged || viewVisibilityChanged) {
                            // If layout params have been changed, first give them
                            // to the window manager to make sure it has the correct
                            // animation info.
                            try {
                                if ((relayoutWindow(mWindowAttributes, viewVisibility, false)
                                        & WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {
                                    mWindowSession.finishDrawing(mWindow);
                                }
                            } catch (RemoteException e) {
                            }
                        }
    
                        mSurface.release();
                    }
                }
    
                mAdded = false;
            }
            WindowManagerGlobal.getInstance().doRemoveView(this);
        }

在doDie里面调用了dispatchDetachedFromWindow()方法，代码如下：

ViewRootImpl.java

**\[java\]** view plain copy

print ?

1.  void dispatchDetachedFromWindow() \{  
2.          if (mView != null && mView.mAttachInfo != null) \{  
3.              mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false);  
4.              mView.dispatchDetachedFromWindow();//看这里，看这里  
5.          \}  
6.    
7.          mAccessibilityInteractionConnectionManager.ensureNoConnection();  
8.          mAccessibilityManager.removeAccessibilityStateChangeListener(  
9.                  mAccessibilityInteractionConnectionManager);  
10.         mAccessibilityManager.removeHighTextContrastStateChangeListener(  
11.                 mHighContrastTextManager);  
12.         removeSendWindowContentChangedCallback();  
13.   
14.         destroyHardwareRenderer();  
15.   
16.         setAccessibilityFocus(null, null);  
17.   
18.         mView.assignParent(null);  
19.         mView = null;  
20.         mAttachInfo.mRootView = null;  
21.   
22.         mSurface.release();  
23.   
24.         if (mInputQueueCallback != null && mInputQueue != null) \{  
25.             mInputQueueCallback.onInputQueueDestroyed(mInputQueue);  
26.             mInputQueue.dispose();  
27.             mInputQueueCallback = null;  
28.             mInputQueue = null;  
29.         \}  
30.         if (mInputEventReceiver != null) \{  
31.             mInputEventReceiver.dispose();  
32.             mInputEventReceiver = null;  
33.         \}  
34.         try \{  
35.             mWindowSession.remove(mWindow);  
36.         \} catch (RemoteException e) \{  
37.         \}  
38.   
39.         // Dispose the input channel after removing the window so the Window Manager  
40.         // doesn’t interpret the input channel being closed as an abnormal termination.  
41.         if (mInputChannel != null) \{  
42.             mInputChannel.dispose();  
43.             mInputChannel = null;  
44.         \}  
45.   
46.         mDisplayManager.unregisterDisplayListener(mDisplayListener);  
47.   
48.         unscheduleTraversals();  
49.     \}

void dispatchDetachedFromWindow() {
            if (mView != null && mView.mAttachInfo != null) {
                mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false);
                mView.dispatchDetachedFromWindow();//看这里，看这里
            }
    
            mAccessibilityInteractionConnectionManager.ensureNoConnection();
            mAccessibilityManager.removeAccessibilityStateChangeListener(
                    mAccessibilityInteractionConnectionManager);
            mAccessibilityManager.removeHighTextContrastStateChangeListener(
                    mHighContrastTextManager);
            removeSendWindowContentChangedCallback();
    
            destroyHardwareRenderer();
    
            setAccessibilityFocus(null, null);
    
            mView.assignParent(null);
            mView = null;
            mAttachInfo.mRootView = null;
    
            mSurface.release();
    
            if (mInputQueueCallback != null && mInputQueue != null) {
                mInputQueueCallback.onInputQueueDestroyed(mInputQueue);
                mInputQueue.dispose();
                mInputQueueCallback = null;
                mInputQueue = null;
            }
            if (mInputEventReceiver != null) {
                mInputEventReceiver.dispose();
                mInputEventReceiver = null;
            }
            try {
                mWindowSession.remove(mWindow);
            } catch (RemoteException e) {
            }
    
            // Dispose the input channel after removing the window so the Window Manager
            // doesn't interpret the input channel being closed as an abnormal termination.
            if (mInputChannel != null) {
                mInputChannel.dispose();
                mInputChannel = null;
            }
    
            mDisplayManager.unregisterDisplayListener(mDisplayListener);
    
            unscheduleTraversals();
        }

还记着在WindowManagerGlobal里面的root.setView(view, wparams, panelParentView);调用吧，这里的mView.dispatchDetachedFromWindow();这个mView也即是上面传过来的view。也就是先看DecorView即ViewGroup里面的dispatchDetachedFromWindow，代码如下：

ViewGroup.java

**\[java\]** view plain copy

print ?

1. @Override  
2. void dispatchDetachedFromWindow() \{  
3.     // If we still have a touch target, we are still in the process of  
4.     // dispatching motion events to a child; we need to get rid of that  
5.     // child to avoid dispatching events to it after the window is torn  
6.     // down. To make sure we keep the child in a consistent state, we  
7.     // first send it an ACTION\_CANCEL motion event.  
8.     cancelAndClearTouchTargets(null);  
9.   
10.     // Similarly, set ACTION\_EXIT to all hover targets and clear them.  
11.     exitHoverTargets();  
12.   
13.     // In case view is detached while transition is running  
14.     mLayoutCalledWhileSuppressed = false;  
15.   
16.     // Tear down our drag tracking  
17.     mDragNotifiedChildren = null;  
18.     if (mCurrentDrag != null) \{  
19.         mCurrentDrag.recycle();  
20.         mCurrentDrag = null;  
21.     \}  
22.   
23.     final int count = mChildrenCount;  
24.     final View\[\] children = mChildren;  
25.     for (int i = 0; i < count; i++) \{  
26.         children\[i\].dispatchDetachedFromWindow();//这里会先调子类的dispatchDetachedFromWindow  
27.     \}  
28.     clearDisappearingChildren();  
29.     final int transientCount = mTransientViews == null ? 0 : mTransientIndices.size();  
30.     for (int i = 0; i < transientCount; ++i) \{  
31.         View view = mTransientViews.get(i);  
32.         view.dispatchDetachedFromWindow();  
33.     \}  
34.     super.dispatchDetachedFromWindow();//然后这里才调用自己的。  
35. \}

@Override
 void dispatchDetachedFromWindow() {
 // If we still have a touch target, we are still in the process of
 // dispatching motion events to a child; we need to get rid of that
 // child to avoid dispatching events to it after the window is torn
 // down. To make sure we keep the child in a consistent state, we
 // first send it an ACTION_CANCEL motion event.
 cancelAndClearTouchTargets(null);
 
 // Similarly, set ACTION_EXIT to all hover targets and clear them.
 exitHoverTargets();
 
 // In case view is detached while transition is running
 mLayoutCalledWhileSuppressed = false;
 
 // Tear down our drag tracking
 mDragNotifiedChildren = null;
 if (mCurrentDrag != null) {
 mCurrentDrag.recycle();
 mCurrentDrag = null;
 }
 
 final int count = mChildrenCount;
 final View[] children = mChildren;
 for (int i = 0; i < count; i++) {
 children[i].dispatchDetachedFromWindow();//这里会先调子类的dispatchDetachedFromWindow
 }
 clearDisappearingChildren();
 final int transientCount = mTransientViews == null ? 0 : mTransientIndices.size();
 for (int i = 0; i < transientCount; ++i) {
 View view = mTransientViews.get(i);
 view.dispatchDetachedFromWindow();
 }
 super.dispatchDetachedFromWindow();//然后这里才调用自己的。
 }

这之后又到View的dispatchDetachedFromWindow了，代码如下：

View.java

**\[java\]** view plain copy

print ?

1. void dispatchDetachedFromWindow() \{  
2.         AttachInfo info = mAttachInfo;  
3.         if (info != null) \{  
4.             int vis = info.mWindowVisibility;  
5.             if (vis != GONE) \{  
6.                 onWindowVisibilityChanged(GONE);  
7.             \}  
8.         \}  
9.   
10.         onDetachedFromWindow();//绕了一大圈，还是找到你了。快看快看，揪出来了。  
11.         onDetachedFromWindowInternal();  
12.   
13.         InputMethodManager imm = InputMethodManager.peekInstance();  
14.         if (imm != null) \{  
15.             imm.onViewDetachedFromWindow(this);  
16.         \}  
17.   
18.         ListenerInfo li = mListenerInfo;  
19.         final CopyOnWriteArrayList<OnAttachStateChangeListener> listeners =  
20.                 li != null ? li.mOnAttachStateChangeListeners : null;  
21.         if (listeners != null && listeners.size() > 0) \{  
22.             // NOTE: because of the use of CopyOnWriteArrayList, we \*must\* use an iterator to  
23.             // perform the dispatching. The iterator is a safe guard against listeners that  
24.             // could mutate the list by calling the various add/remove methods. This prevents  
25.             // the array from being modified while we iterate it.  
26.             for (OnAttachStateChangeListener listener : listeners) \{  
27.                 listener.onViewDetachedFromWindow(this);  
28.             \}  
29.         \}  
30.   
31.         if ((mPrivateFlags & PFLAG\_SCROLL\_CONTAINER\_ADDED) != 0) \{  
32.             mAttachInfo.mScrollContainers.remove(this);  
33.             mPrivateFlags &= ~PFLAG\_SCROLL\_CONTAINER\_ADDED;  
34.         \}  
35.   
36.         mAttachInfo = null;  
37.         if (mOverlay != null) \{  
38.             mOverlay.getOverlayView().dispatchDetachedFromWindow();  
39.         \}  
40.     \}

void dispatchDetachedFromWindow() {
 AttachInfo info = mAttachInfo;
 if (info != null) {
 int vis = info.mWindowVisibility;
 if (vis != GONE) {
 onWindowVisibilityChanged(GONE);
 }
 }
 
 onDetachedFromWindow();//绕了一大圈，还是找到你了。快看快看，揪出来了。
 onDetachedFromWindowInternal();
 
 InputMethodManager imm = InputMethodManager.peekInstance();
 if (imm != null) {
 imm.onViewDetachedFromWindow(this);
 }
 
 ListenerInfo li = mListenerInfo;
 final CopyOnWriteArrayList<OnAttachStateChangeListener> listeners =
 li != null ? li.mOnAttachStateChangeListeners : null;
 if (listeners != null && listeners.size() > 0) {
 // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
 // perform the dispatching. The iterator is a safe guard against listeners that
 // could mutate the list by calling the various add/remove methods. This prevents
 // the array from being modified while we iterate it.
 for (OnAttachStateChangeListener listener : listeners) {
 listener.onViewDetachedFromWindow(this);
 }
 }
 
 if ((mPrivateFlags & PFLAG_SCROLL_CONTAINER_ADDED) != 0) {
 mAttachInfo.mScrollContainers.remove(this);
 mPrivateFlags &= ~PFLAG_SCROLL_CONTAINER_ADDED;
 }
 
 mAttachInfo = null;
 if (mOverlay != null) {
 mOverlay.getOverlayView().dispatchDetachedFromWindow();
 }
 }

看代码终于找到了onDetachedFromWindow的调用地方了。

这里总结下：

1.onAttachedToWindow调用顺序：ActivityThread.handleResumeActivity->WindowManagerImpl.addView->WindowManagerGlobal.addView->ViewRootImpl.performTraversals->ViewGroup.dispatchAttachedToWindow->View.dispatchAttachedToWindow->onAttachedToWindow

2.onDetachedFromWindow调用顺序：ActivityThread.handleDestroyActivity->WindowManagerImpl.removeViewImmediate->WindowManagerGlobal.removeView->ViewRootImpl.die->ViewRootImpl.doDie->ViewRootImpl.dispatchDetachedFromWindow->ViewGroup.dispatchDetachedFromWindow->View.dispatchDetachedFromWindow->onDetachedToWindow

3.onAttachedToWindow和onDetachedFromWindow的调用与visibility无关。

4.onAttachedToWindow是先调用自己，然后调用儿子View的。onDetachedFromWindow是先调用儿子View的，然后再调用自己的。

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