各种Window的创建过程

今天药忘吃喽~ 2023-10-17 10:17 3阅读 0赞

## Window的创建过程 ##

### Window是View的直接管理者 ###

![Window是View的直接管理者][Window_View]

> 图片源自[https://mp.weixin.qq.com/s/IrwjQqlDoLp3xQZbthncVg][https_mp.weixin.qq.com_s_IrwjQqlDoLp3xQZbthncVg]

### Activity的Window创建过程 ###

Activity的启动最终会通过ActivityThread\#performLaunchActivity()来完成。

ActivityThread\#performLaunchActivity()

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
        //...
        //通过类加载器创建Activity实例
        java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
        activity = mInstrumentation.newActivity(
                cl, component.getClassName(), r.intent);
       //...
    
        Application app = r.packageInfo.makeApplication(false, mInstrumentation);
    
        Context appContext = createBaseContextForActivity(r, activity);
        CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
        Configuration config = new Configuration(mCompatConfiguration);
    
        //关联运行过程中所依赖的一系列上下文环境变量
        activity.attach(appContext, this, getInstrumentation(), r.token,
                r.ident, app, r.intent, r.activityInfo, title, r.parent,
                r.embeddedID, r.lastNonConfigurationInstances, config,
                r.voiceInteractor);
    
        mActivities.put(r.token, r);
        return activity;
    }

在attach方法里，系统会创建Activity所属的Window对象并为其设置回调接口。

Activity\#attach()

final void attach(Context context, ActivityThread aThread,
            Instrumentation instr, IBinder token, int ident,
            Application application, Intent intent, ActivityInfo info,
            CharSequence title, Activity parent, String id,
            NonConfigurationInstances lastNonConfigurationInstances,
            Configuration config, IVoiceInteractor voiceInteractor) {
    
        attachBaseContext(context);
        mFragments.attachActivity(this, mContainer, null);
    
        //创建Window对象
        mWindow = PolicyManager.makeNewWindow(this);
        //设置回调 比如我们熟悉的onAttachedToWindow、onDetachedFromWindow、dispatchTouchEvent
        //[重要] 当Window接收到外界的状态改变时就会调用Activity实现的回调
        mWindow.setCallback(this);
        mWindow.setOnWindowDismissedCallback(this);
    
        //赋值
        if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
            mWindow.setSoftInputMode(info.softInputMode);
        }
        if (info.uiOptions != 0) {
            mWindow.setUiOptions(info.uiOptions);
        }
        mUiThread = Thread.currentThread();
        mMainThread = aThread;
        mInstrumentation = instr;
        mToken = token;
        mIdent = ident;
        mApplication = application;
        mIntent = intent;
        mComponent = intent.getComponent();
        mActivityInfo = info;
        mTitle = title;
        mParent = parent;
        mEmbeddedID = id;
        mLastNonConfigurationInstances = lastNonConfigurationInstances;
    
        //...       
    
        //设置WindowManager
        mWindow.setWindowManager(
                (WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
                mToken, mComponent.flattenToString(),
                (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
        if (mParent != null) {
            mWindow.setContainer(mParent.getWindow());
        }
        mWindowManager = mWindow.getWindowManager();
        mCurrentConfig = config;
    }

再来看 PolicyManager.makeNewWindow(this)，PilicyManager的真正实现类是Policy类。  
位于source\\frameworks\\base\\policy\\src\\com\\android\\internal\\policy\\impl\\Policy.java

public Window makeNewWindow(Context context) {
        return new PhoneWindow(context);
    }

可以发现Window的实现类确实是PhoneWindow。

Window初始完毕后，再来看Activity的视图是如何依附在Window上的。Activity的视图通过setContent方法提供。

public void setContentView(int layoutResID) {
        getWindow().setContentView(layoutResID);
        initWindowDecorActionBar();
    }

可以发现，Activity的setContentView将具体实现交由Window处理。

phoneWindow\#setContentView()

@Override
    public void setContentView(int layoutResID) {
        // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
        // decor, when theme attributes and the like are crystalized. Do not check the feature
        // before this happens.
        //1.创建DecorView (如果没有创建的话)
        if (mContentParent == null) {
            installDecor();
        } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
            mContentParent.removeAllViews();
        }
    
        if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
            final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
                    getContext());
            transitionTo(newScene);
            //2.将View添加到DecorView的mContentParent中
            mLayoutInflater.inflate(layoutResID, mContentParent);
        }
        //3.回调Activity的onContentChanged()通知Activity视图已经发生改变
        final Callback cb = getCallback();
        if (cb != null && !isDestroyed()) {
            cb.onContentChanged();
        }
    }

经过setContentView方法，DecorView已经被创建并初始化完毕，Activity的布局文件也已经成功添加到DecorView的mContentParent中，但这个时候DecorView还没有被WindowManager添加到Window中。 (在添加之前)

##### \# #####

*  Activity的attach()中，Window被创建并初始化
 *  在Activity的setContentView中 (PhoneWindow\#setContentView)，DecorView被创建 (如果没被创建的话)
 *  而在ActivityThread\#handleResumeActivity首先会调用Activity的onResume方法中，接着会先将DecorView设为不可见(INVISIBLE)，然后会调用Activity的makeVisible()，在makeVisible()中，将DecorView添加到Window并置为Visible。

##### \# #####

void makeVisible() {
        //将DecorView添加到Window
        if (!mWindowAdded) {
            ViewManager wm = getWindowManager();
            wm.addView(mDecor, getWindow().getAttributes());
            mWindowAdded = true;
        }
        //将Activity的显示置为Visible
        mDecor.setVisibility(View.VISIBLE);
    }

### Dialog的window创建过程 ###

Dialog的Window创建过程和Activity类似

Dialog\#构造方法

Dialog(Context context, int theme, boolean createContextThemeWrapper) {
        //...        
        mContext = context;
    
        mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
        //创建Window对象
        Window w = PolicyManager.makeNewWindow(mContext);
        mWindow = w;
        w.setCallback(this);
        w.setOnWindowDismissedCallback(this);
        w.setWindowManager(mWindowManager, null, null);
        w.setGravity(Gravity.CENTER);
        mListenersHandler = new ListenersHandler(this);
    }

再来看Dialog\#setContentView()

public void setContentView(int layoutResID) {
        mWindow.setContentView(layoutResID);
    }

同样是交由Window处理。

当Dialog dismiss时，会通过WindowManager来移除DecorView

@Override
    public void dismiss() {
        if (Looper.myLooper() == mHandler.getLooper()) {
            dismissDialog();
        } else {
            mHandler.post(mDismissAction);
        }
    }
    
    void dismissDialog() {
        //...
        //移除DecorView
        mWindowManager.removeViewImmediate(mDecor);
       //...
    }

#### 注意 ####

普通Dialog需要使用Activity的Content  
因为Window需要应用token，而应用token一般只有Activity才拥有。  
系统Window比较特殊，它可以不需要token。

### Toast的Window创建过程 ###

Toast属于系统Window  
Toast内部有两类IPC过程

1.  Toast访问NotifationManagerService
2.  NotificationManagerService回调Toast的TN接口

Toast提供了show和cancel分别用于显示和隐藏Toast \[都是IPC过程\]

public void show() {
        if (mNextView == null) {
            throw new RuntimeException("setView must have been called");
        }
    
        INotificationManager service = getService();
        String pkg = mContext.getOpPackageName();
        TN tn = mTN;
        tn.mNextView = mNextView;
    
        try {
            service.enqueueToast(pkg, tn, mDuration);
        } catch (RemoteException e) {
            // Empty
        }
    }  
    
    public void cancel() {
        mTN.hide();
    
        try {
            getService().cancelToast(mContext.getPackageName(), mTN);
        } catch (RemoteException e) {
            // Empty
        }
    }

主要来看enqueueToast()

//参数一:当前应用的包名
    //参数二:远程回调
    //参数三:Toast的时长
    //enqueueToast首先将Toast封装为ToastRecord对象并将其添加到一个名为mToastQueue的队列中
    service.enqueueToast(pkg, tn, mDuration);

当ToastRecord被添加到mToastQueue中后，Inotifacationmanager就会通过showNextToastLacked方法来显示当前的Toast。

NotificationManagerService\#showNextToastLocked()

void showNextToastLocked() {
        //获取下一个ToastRecord
        ToastRecord record = mToastQueue.get(0);
        while (record != null) {
            if (DBG) Slog.d(TAG, "Show pkg=" + record.pkg + " callback=" + record.callback);
            try {
                //record.callback就是Toast.java类中的TN (Binder) 对象
                record.callback.show();
                //发送延迟消息来移除toast
                //scheduleTimeoutLocked -> mHandler.sendMessageDelayed -> cancelToastLocked -> record.callback.hide();
                scheduleTimeoutLocked(record);
                return;
            } catch (RemoteException e) {
                Slog.w(TAG, "Object died trying to show notification " + record.callback
                        + " in package " + record.pkg);
                // remove it from the list and let the process die
                int index = mToastQueue.indexOf(record);
                if (index >= 0) {
                    mToastQueue.remove(index);
                }
                keepProcessAliveLocked(record.pid);
                if (mToastQueue.size() > 0) {
                    record = mToastQueue.get(0);
                } else {
                    record = null;
                }
            }
        }
    }

可以发现，Toast的显示和移除都是通过Toast的TN类(Binder对象)来完成的。

Toast内部类TN

private static class TN extends ITransientNotification.Stub {
        final Runnable mShow = new Runnable() {
            @Override
            public void run() {
                handleShow();
            }
        };
    
        final Runnable mHide = new Runnable() {
            @Override
            public void run() {
                handleHide();
                // Don't do this in handleHide() because it is also invoked by handleShow()
                mNextView = null;
            }
        };
    
        @Override
        public void show() {
            if (localLOGV) Log.v(TAG, "SHOW: " + this);
            mHandler.post(mShow);
        }
    
        @Override
        public void hide() {
            if (localLOGV) Log.v(TAG, "HIDE: " + this);
            mHandler.post(mHide);
        }
    
        //...
    }

真正的显示

public void handleShow() {
            //...
            mWM = (WindowManager)context.getSystemService
            //...
            if (mView.getParent() != null) {
                mWM.removeView(mView);
            }
            mWM.addView(mView, mParams);
            //...
        }
    }

真正的隐藏

public void handleHide() {
        if (mView != null) {
            if (mView.getParent() != null) {
                mWM.removeView(mView);
            }
            mView = null;
        }
    }

#### 相关 ####

[PhoneWindow伪代码][PhoneWindow]

[Window_View]: http://mmbiz.qpic.cn/mmbiz_png/v1LbPPWiaSt70mzD2HFibu9ly96JPmm12ttaEAbYuWXr8qL9mL6qf2rNyTsR4QkqeV7C4MlYRTtrLtEHnAQG4nJg/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1
[https_mp.weixin.qq.com_s_IrwjQqlDoLp3xQZbthncVg]: https://mp.weixin.qq.com/s/IrwjQqlDoLp3xQZbthncVg
[PhoneWindow]: https://github.com/EthanCo/PettyModules/blob/master/%E4%BC%AA%E4%BB%A3%E7%A0%81/PhoneWindow.java