android中调用requestFocus()的详细过程

柔情只为你懂 2022-01-09 12:11 361阅读 0赞

view中
            
    public boolean requestFocus(int direction, Rect previouslyFocusedRect) {
            return requestFocusNoSearch(direction, previouslyFocusedRect);
            }
    
    private boolean requestFocusNoSearch(int direction, Rect previouslyFocusedRect) {
            // need to be focusable  
            if ((mViewFlags & FOCUSABLE_MASK) != FOCUSABLE ||
            (mViewFlags & VISIBILITY_MASK) != VISIBLE) {
            return false;
            }
    
            // need to be focusable in touch mode if in touch mode  
            if (isInTouchMode() &&
            (FOCUSABLE_IN_TOUCH_MODE != (mViewFlags & FOCUSABLE_IN_TOUCH_MODE))) {
            return false;
            }
    
            // need to not have any parents blocking us  
            if (hasAncestorThatBlocksDescendantFocus()) {//判断父视图是否阻止子视图获得焦点  
            return false;
            }
    
            handleFocusGainInternal(direction, previouslyFocusedRect);//进行具体的焦点获取  
            return true;
            }
            
            void handleFocusGainInternal(int direction, Rect previouslyFocusedRect) {
            if (DBG) {
            System.out.println(this + " requestFocus()");
            }
    
            if ((mPrivateFlags & FOCUSED) == 0) {
            mPrivateFlags |= FOCUSED;
    
            if (mParent != null) {
            mParent.requestChildFocus(this, this);//第一个参数是child视图，第二个是focused视图，该函数内部进行递归调用  
            }
            //注意时态，xxxed()和xxx()的区别是，前者是执行完之后回调，后者是在执行前回调  
            onFocusChanged(true, direction, previouslyFocusedRect);
            refreshDrawableState();
    
            if (AccessibilityManager.getInstance(mContext).isEnabled()) {
            notifyAccessibilityStateChanged();
            }
            }
            }
            一般来说，父视图是ViewGroup，requestChildFocus在ViewGroup中的实现
            
    public void requestChildFocus(View child, View focused) {
            if (DBG) {
            System.out.println(this + " requestChildFocus()");
            }
            if (getDescendantFocusability() == FOCUS_BLOCK_DESCENDANTS) {
            return;
            }
    
            // Unfocus us, if necessary  
            super.unFocus();
    
            // We had a previous notion of who had focus. Clear it.  
            if (mFocused != child) {
            if (mFocused != null) {
            mFocused.unFocus();
            }
    
            mFocused = child;
            }
            if (mParent != null) {
            mParent.requestChildFocus(this, focused);//最终会递归到ViewRoot中的equestChildFocus  
            }
            }
            ViewRootImpl中的requestChildFocus
            
    public void requestChildFocus(View child, View focused) {
            checkThread();//确保在UI线程中  
            if (mFocusedView != focused) {//其实ViewGroup中已经检查过，mFocusedView一定不是目标焦点视图  
            mAttachInfo.mTreeObserver.dispatchOnGlobalFocusChange(mFocusedView, focused);
            scheduleTraversals();//发起View遍历请求  
            }
            mFocusedView = mRealFocusedView = focused;
            if (DEBUG_INPUT_RESIZE) Log.v(TAG, "Request child focus: focus now "
            + mFocusedView);  view中
            
    public boolean requestFocus(int direction, Rect previouslyFocusedRect) {
            return requestFocusNoSearch(direction, previouslyFocusedRect);
            }
    
    private boolean requestFocusNoSearch(int direction, Rect previouslyFocusedRect) {
            // need to be focusable  
            if ((mViewFlags & FOCUSABLE_MASK) != FOCUSABLE ||
            (mViewFlags & VISIBILITY_MASK) != VISIBLE) {
            return false;
            }
    
            // need to be focusable in touch mode if in touch mode  
            if (isInTouchMode() &&
            (FOCUSABLE_IN_TOUCH_MODE != (mViewFlags & FOCUSABLE_IN_TOUCH_MODE))) {
            return false;
            }
    
            // need to not have any parents blocking us  
            if (hasAncestorThatBlocksDescendantFocus()) {//判断父视图是否阻止子视图获得焦点  
            return false;
            }
    
            handleFocusGainInternal(direction, previouslyFocusedRect);//进行具体的焦点获取  
            return true;
            }
            
            void handleFocusGainInternal(int direction, Rect previouslyFocusedRect) {
            if (DBG) {
            System.out.println(this + " requestFocus()");
            }
    
            if ((mPrivateFlags & FOCUSED) == 0) {
            mPrivateFlags |= FOCUSED;
    
            if (mParent != null) {
            mParent.requestChildFocus(this, this);//第一个参数是child视图，第二个是focused视图，该函数内部进行递归调用  
            }
            //注意时态，xxxed()和xxx()的区别是，前者是执行完之后回调，后者是在执行前回调  
            onFocusChanged(true, direction, previouslyFocusedRect);
            refreshDrawableState();
    
            if (AccessibilityManager.getInstance(mContext).isEnabled()) {
            notifyAccessibilityStateChanged();
            }
            }
            }
            一般来说，父视图是ViewGroup，requestChildFocus在ViewGroup中的实现
            
    public void requestChildFocus(View child, View focused) {
            if (DBG) {
            System.out.println(this + " requestChildFocus()");
            }
            if (getDescendantFocusability() == FOCUS_BLOCK_DESCENDANTS) {
            return;
            }
    
            // Unfocus us, if necessary  
            super.unFocus();
    
            // We had a previous notion of who had focus. Clear it.  
            if (mFocused != child) {
            if (mFocused != null) {
            mFocused.unFocus();
            }
    
            mFocused = child;
            }
            if (mParent != null) {
            mParent.requestChildFocus(this, focused);//最终会递归到ViewRoot中的equestChildFocus  
            }
            }
            ViewRootImpl中的requestChildFocus
            
    public void requestChildFocus(View child, View focused) {
            checkThread();//确保在UI线程中  
            if (mFocusedView != focused) {//其实ViewGroup中已经检查过，mFocusedView一定不是目标焦点视图  
            mAttachInfo.mTreeObserver.dispatchOnGlobalFocusChange(mFocusedView, focused);
            scheduleTraversals();//发起View遍历请求  
            }
            mFocusedView = mRealFocusedView = focused;
            if (DEBUG_INPUT_RESIZE) Log.v(TAG, "Request child focus: focus now " + mFocusedView);