|  |  |  | @ -52,3 +52,58 @@ public boolean dispatchTouchEvent (MotionEvent event) { | 
			
		
	
		
			
				
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					|  |  |  |  | #### ViewGroup 中 TouchEvent 的投递流程 | 
			
		
	
		
			
				
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					|  |  |  |  | ViewGroup 因为涉及对子 View 的处理,其派发流程没有 View 那么简单直接,它重写了 dispatchTouchEvent 方法: | 
			
		
	
		
			
				
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					|  |  |  |  | ```java | 
			
		
	
		
			
				
					|  |  |  |  | public boolean dispatchTouchEvent(MotionEvent ev) { | 
			
		
	
		
			
				
					|  |  |  |  |     boolean handled = false; | 
			
		
	
		
			
				
					|  |  |  |  |     if (onFilterTouchEventForSecurity(ev)) { | 
			
		
	
		
			
				
					|  |  |  |  |         final int action = ev.getAction(); | 
			
		
	
		
			
				
					|  |  |  |  |         final int actionMasked = action & MotionEvent.ACTION_MASK; | 
			
		
	
		
			
				
					|  |  |  |  |         if (actionMasked == MotionEvent.ACTION_DOWN) { | 
			
		
	
		
			
				
					|  |  |  |  |             cancelAndClearTouchTargets(ev); | 
			
		
	
		
			
				
					|  |  |  |  |             resetTouchState(); | 
			
		
	
		
			
				
					|  |  |  |  |         } | 
			
		
	
		
			
				
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					|  |  |  |  |         final boolean intercepted; | 
			
		
	
		
			
				
					|  |  |  |  |         if (actionMasked == MotionEvent.ACTION_DOWN | 
			
		
	
		
			
				
					|  |  |  |  |                 || mFirstTouchTarget != null) { | 
			
		
	
		
			
				
					|  |  |  |  |             final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; | 
			
		
	
		
			
				
					|  |  |  |  |             if (!disallowIntercept) { | 
			
		
	
		
			
				
					|  |  |  |  |                 intercepted = onInterceptTouchEvent(ev); | 
			
		
	
		
			
				
					|  |  |  |  |                 ev.setAction(action);  | 
			
		
	
		
			
				
					|  |  |  |  |             } else { | 
			
		
	
		
			
				
					|  |  |  |  |                 intercepted = false; | 
			
		
	
		
			
				
					|  |  |  |  |             } | 
			
		
	
		
			
				
					|  |  |  |  |         } else { | 
			
		
	
		
			
				
					|  |  |  |  |             intercepted = true; | 
			
		
	
		
			
				
					|  |  |  |  |         } | 
			
		
	
		
			
				
					|  |  |  |  |         // 不拦截的情况 | 
			
		
	
		
			
				
					|  |  |  |  |         if (actionMasked == MotionEvent.ACTION_DOWN | 
			
		
	
		
			
				
					|  |  |  |  |             || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN) | 
			
		
	
		
			
				
					|  |  |  |  |             || actionMasked == MotionEvent.ACTION_HOVER_MOVE) { | 
			
		
	
		
			
				
					|  |  |  |  |             final int actionIndex = ev.getActionIndex(); | 
			
		
	
		
			
				
					|  |  |  |  |             final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex) | 
			
		
	
		
			
				
					|  |  |  |  |                 : TouchTarget.ALL_POINTER_IDS; | 
			
		
	
		
			
				
					|  |  |  |  |             final int childrenCount = mChildrenCount; | 
			
		
	
		
			
				
					|  |  |  |  |             if (newTouchTarget == null && childrenCount != 0) { | 
			
		
	
		
			
				
					|  |  |  |  |                 final float x = ev.getX(actionIndex); | 
			
		
	
		
			
				
					|  |  |  |  |                 final float y = ev.getY(actionIndex); | 
			
		
	
		
			
				
					|  |  |  |  |                 final View[] children = mChildren; | 
			
		
	
		
			
				
					|  |  |  |  |                 for (int i = childrenCount - 1; i >= 0; i--) { | 
			
		
	
		
			
				
					|  |  |  |  |                     if (!child.canReceivePointerEvents() | 
			
		
	
		
			
				
					|  |  |  |  |                         || !isTransformedTouchPointInView(x, y, child, null)) { | 
			
		
	
		
			
				
					|  |  |  |  |                         continue; | 
			
		
	
		
			
				
					|  |  |  |  |                         newTouchTarget = getTouchTarget(child); | 
			
		
	
		
			
				
					|  |  |  |  |                         if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { | 
			
		
	
		
			
				
					|  |  |  |  |                             break; | 
			
		
	
		
			
				
					|  |  |  |  |                         } | 
			
		
	
		
			
				
					|  |  |  |  |                     } | 
			
		
	
		
			
				
					|  |  |  |  |                 } | 
			
		
	
		
			
				
					|  |  |  |  |             } | 
			
		
	
		
			
				
					|  |  |  |  |         } | 
			
		
	
		
			
				
					|  |  |  |  |     } | 
			
		
	
		
			
				
					|  |  |  |  | } | 
			
		
	
		
			
				
					|  |  |  |  | ``` | 
			
		
	
		
			
				
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					|  |  |  |  | 如果 ViewGroup 允许拦截,就调用其 onInterceptTouchEvent 来判断是否要真正执行拦截了,这样做了是方便扩展。如果不拦截,就从后遍历子 View 处理。它有两个函数可以过滤子 View,一个是判断这个子 View 能否接收 Pointer Events 事件,另一个是判断落点有没有落在子 View 范围内。如果都满足,则调用其 dispatchTouchEvent 处理。如果该子 View 是一个 ViewGroup 就继续调用其 dispatchTouchEvent,否则就是 View 的 dispatchTouchEvent。如此循环往复,直到事件真正被处理。 |