Android4.4   Input模块笔记

在InputReader从EventHub中获取输入事件，包含触摸屏事件、物理按键事件等，然后转交给InputDispatcher线程，InputDispatcher经过筛选，过滤输入事件。对于触摸事件通过调用findTouchedWindowTargetsLocked()函数找到合适的InputTarget，然后通过dispatchEventLocked()->prepareDispatchCycleLocked()->enqueueDispatchEntriesLocked()->enqueueDispatchEntryLocked()->  connection->outboundQueue.enqueueAtTail(dispatchEntry)添加到与InputTarget一一对应的connection中的一个队列中。如果之前该队列无数据，并且当前触摸事件已成功加入该队列，则继续调用startDispatchCycleLocked()函数进行分发处理。在startDispatchCycleLocked()中，有一个while循环，该循环从connection->outboundQueue队列中取出输入事件，如果该输入事件是按键（key）事件，则调用connection->inputPublisher.publishKeyEvent()函数，如果是触摸事件则调用connection->inputPublisher.publishMotionEvent（）。publishKeyEvent()和publishMotionEvent()都是调用mChannel->sendMessage()将输入事件发送出去。mChannel是一个C++层InputChannel对象，该对象的赋值过程如下：registerInputChannel()->new Connection->Connection()构造函数->InputPublisher()构造函数。事实上，在registerInputChannel()被调用之前，ViewRootImple在增加一个窗口时调用ViewRootImpl.setView()->mWindowSession.addToDisplay()-WindowManagerService.addWindow()，在addWindow()中会创建一对InputChannel（Nativie层），实际上是创建一对Socket，服务端InputChanel被WMS注册到InputDispatcher中，客户端InputChannel被返回给ViewRootImpl，ViewRootImpl将客户端InputChannel作为参数new一个InputEventReceiver对象，在InputEventReceiver()构造函数中继续调用nativeInit()函数来创建一个native层的NativeInputEventReceiver对象，前面创建的客户端InputChannel会保存在该对象中。

总结：WMS会调用native层接口创建一对套接字，服务端保存在InputDispatcher中，客户端保存在NativeInputEventReceiver中（android_view_inputEventReceiver.cpp）。

很容易想到输入事件是从InputDispatcher流向NativeInputEventReceiver中。在创建一个native层的NativeInputEventReceiver对象后会立即调用NativeInputEventReceiver->initialize()，该函数调用mMessageQueue->getLooper()->addFd(fd,0, events, this, NULL)将客户端socket句柄添加到Looper的轮询队列中，参数this指向NativeInputEventReceiver本身，意味着只要服务端InputDispatcher发送输入事件，客户端收到这个事件，就调用NativeInputEventReceiver的某个函数，具体调用哪个函数，自然是NativeInputEventReceiver实现了LooperCallback的接口函数handleEvent()。但此时收到的事件只是代表socket客户端有事件来，并没有把具体的事件读取出来，这点需要注意。

总结：客户端收到输入事件，即调用NativeInputEventReceiver->handleEvent()函数。

在handleEvent()函数中，继续调用consumeEvents()->mInputConsumer.consume()->mChannel->receiveMessage(&mMsg)将具体输入事件读取出来，然后调用env->CallVoidMethod(receiverObj.get(), gInputEventReceiverClassInfo.dispatchInputEvent,seq, inputEventObj)，可以知道native层读取输入事件后，然后会回调java层InputEventReceiver.java中的dispatchInputEvent()函数。事实上，

dispatchInputEvent继续调用onInputEvent(event); 此时可能并不调用InputEventReceiver类中的onInputEvent()方法，而是调用子类onInputEvent()方法。在 ViewRootImpl中存在WindowInputEventReceiver类型变量 mInputEventReceiver，WindowInputEventReceiver类继承InputEventReceiver，并实现 onInputEvent()方法由此可得出结论：native层socket客户端读取输入事件，最终调用InputEventReceiver类子类 的onInputEvent()方法，ViewRootImpl继承InputEventReceiver，因此 ViewRootImpl.onInputEvent()将被调用。

总结：对于一般的触摸屏事件最终处理者是ViewRootImpl类，对于输入法则处理者是IInputMethodSessionWrapper类，当然WMS是不会处理这些输入事件的。

继 续研究ViewRootImpl.onInputEvent()函 数，onInputEvent()->doProcessInputEvents()->deliverInputEvent()，deliverInputEvent() 函数中会调用stage.deliver(q)，stage是mFirstPostImeInputStage 或 mFirstInputStage，这个两个InputStage对象在setView中赋值。InputStage类设计就是责任链模式。因为触摸事件是要分发到具体的View上来，所以对于一般的触摸事件最后是传递到ViewPostImeInputStage类中来处理，处理函数是processPointerEvent(q)，这个函数调用mView.dispatchPointerEvent(event)将事件分发出去，mView具体是什么呢？mView其实就是DecorView，每一个窗口有且仅有一个DecorView，且处在最顶层，由于DecorView未重写dispatchPointerEvent()，所以调用还是父类View类的dispatchPointerEvent()方法。

[java] view plaincopy

1. public final boolean dispatchPointerEvent(MotionEvent event) {  

2.         if (event.isTouchEvent()) {  

3.             return dispatchTouchEvent(event);  

4.         } else {  

5.             return dispatchGenericMotionEvent(event);  

6.         }  

7.     }  

该方法继续调用dispatchTouchEvent(event)，DecorView重新了该方法：

[java] view plaincopy

1. @Override  

2.         public boolean dispatchTouchEvent(MotionEvent ev) {  

3.             final Callback cb = getCallback();  

4.             return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev)  

5.                     : super.dispatchTouchEvent(ev);  

6.         }  

getCallback() 函数获取apk注册的用于拦截按键、触摸等事件的回调函数。一般window不会拦截处理触摸事件，所以会继续调用 super.dispatchTouchEvent(ev)，即父类ViewGroup的dispatchTouchEvent()函数，在该函数中寻找 到对应的View再继续调用dispatchTransformedTouchEvent()

[java] view plaincopy

1. for (int i = childrenCount - 1; i >= 0; i--) {  

2.                           final int childIndex = customOrder ?  

3.                                   getChildDrawingOrder(childrenCount, i) : i;  

4.                           final View child = children[childIndex];  

5.                           if (!canViewReceivePointerEvents(child)  

6.                                   || !isTransformedTouchPointInView(x, y, child, null)) {  

7.                               continue;  

8.                           }  

9.   

10.                           newTouchTarget = getTouchTarget(child);  

11.                           if (newTouchTarget != null) {  

12.                               // Child is already receiving touch within its bounds.  

13.                               // Give it the new pointer in addition to the ones it is handling.  

14.                               newTouchTarget.pointerIdBits |= idBitsToAssign;  

15.                               break;  

16.                           }  

17.   

18.                           resetCancelNextUpFlag(child);  

19.                           if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {  

20.                               // Child wants to receive touch within its bounds.  

21.                               mLastTouchDownTime = ev.getDownTime();  

22.                               mLastTouchDownIndex = childIndex;  

23.                               mLastTouchDownX = ev.getX();  

24.                               mLastTouchDownY = ev.getY();  

25.                               newTouchTarget = addTouchTarget(child, idBitsToAssign);  

26.                               alreadyDispatchedToNewTouchTarget = true;  

27.                               break;  

28.                           }  

29.                        

具体的分发规则可自行研究代码。

ViewGroup.dispatchTouchEvent()函数分析

[html] view plaincopy

1. @Override  

2. public boolean dispatchTouchEvent(MotionEvent ev) {  

3.     if (mInputEventConsistencyVerifier != null) {  

4.         mInputEventConsistencyVerifier.onTouchEvent(ev, 1);  

5.     }  

6.   

7.     if (DBG_MOTION || DBG_TOUCH) {  

8.         Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent 1: ev = " + ev + ",mFirstTouchTarget = "  

9.                 + mFirstTouchTarget + ",this = " + this);  

10.     }  

11.   

12.     boolean handled = false;  

13.     if (onFilterTouchEventForSecurity(ev)) {  

14.         final int action = ev.getAction();  

15.         final int actionMasked = action & MotionEvent.ACTION_MASK;  

16.   

17.         // Handle an initial down.  

18.         if (actionMasked == MotionEvent.ACTION_DOWN) {  

19.             // Throw away all previous state when starting a new touch gesture.  

20.             // The framework may have dropped the up or cancel event for the previous gesture  

21.             // due to an app switch, ANR, or some other state change.  

22.             cancelAndClearTouchTargets(ev);  

23.             resetTouchState();  

24.         }  

25.   

26.         // Check for interception.  

27.         final boolean intercepted;  

28.         if (actionMasked == MotionEvent.ACTION_DOWN  

29.                 || mFirstTouchTarget != null) {  

30.             final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;  

31.             if (!disallowIntercept) {  

32.                 intercepted = onInterceptTouchEvent(ev);  

33.                 /// M : add log to help debugging  

34.                 if (intercepted == true) {  

35.                     if (DBG_TOUCH) {  

36.                         Xlog.d(TAG, "Touch event was intercepted event = " + ev + ",this = " + this);  

37.                     }  

38.                 }  

39.                 ev.setAction(action); // restore action in case it was changed  

40.             } else {  

41.                 intercepted = false;  

42.             }  

43.         } else {  

44.             // There are no touch targets and this action is not an initial down  

45.             // so this view group continues to intercept touches.  

46.             intercepted = true;  

47.         }  

48.   

49.         // Check for cancelation.  

50.         final boolean canceled = resetCancelNextUpFlag(this)  

51.                 || actionMasked == MotionEvent.ACTION_CANCEL;  

52.   

53.         // Update list of touch targets for pointer down, if needed.  

54.         final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;  

55.         if (DBG_MOTION) {  

56.             Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent 2: actionMasked = " + actionMasked  

57.                     + ",intercepted = " + intercepted + ",canceled = " + canceled + ",split = "  

58.                     + split + ",mChildrenCount = " + mChildrenCount + ",mFirstTouchTarget = "  

59.                     + mFirstTouchTarget + ",this = " + this);  

60.         }  

61.   

62.         TouchTarget newTouchTarget = null;  

63.         boolean alreadyDispatchedToNewTouchTarget = false;  

64.         if (!canceled && !intercepted) {  

65.             if (actionMasked == MotionEvent.ACTION_DOWN  

66.                     || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)  

67.                     || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {  

68.                 final int actionIndex = ev.getActionIndex(); // always 0 for down  

69.                 final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex)  

70.                         : TouchTarget.ALL_POINTER_IDS;  

71.   

72.                 // Clean up earlier touch targets for this pointer id in case they  

73.                 // have become out of sync.  

74.                 removePointersFromTouchTargets(idBitsToAssign);  

75.   

76.                 final int childrenCount = mChildrenCount;  

77.                 if (newTouchTarget == null && childrenCount != 0) {  

78.                     final float x = ev.getX(actionIndex);  

79.                     final float y = ev.getY(actionIndex);  

80.                     // Find a child that can receive the event.  

81.                     // Scan children from front to back.  

82.                     final View[] children = mChildren;  

83.   

84.                     final boolean customOrder = isChildrenDrawingOrderEnabled();  

85.                     for (int i = childrenCount - 1; i >= 0; i--) {  

86.                         final int childIndex = customOrder ?  

87.                                 getChildDrawingOrder(childrenCount, i) : i;  

88.                         final View child = children[childIndex];  

89.                         if (!canViewReceivePointerEvents(child)  

90.                                 || !isTransformedTouchPointInView(x, y, child, null)) {  

91.                             if (DBG_MOTION) {  

92.                                 Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent continue 6: i = "  

93.                                         + i + ",count = " + childrenCount + ",child = " + child  

94.                                         + ",this = " + this);  

95.                             }  

96.                             continue;  

97.                         }  

98.   

99.                         newTouchTarget = getTouchTarget(child);  

100.                         if (DBG_MOTION) {  

101.                             Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent to child 3: child = "  

102.                                     + child + ",childrenCount = " + childrenCount + ",i = " + i  

103.                                     + ",newTouchTarget = " + newTouchTarget + ",idBitsToAssign = "   

104.                                     + idBitsToAssign + ",mFirstTouchTarget = " + mFirstTouchTarget   

105.                                     + ",this = " + this);  

106.                         }  

107.                         if (newTouchTarget != null) {  

108.                             // Child is already receiving touch within its bounds.  

109.                             // Give it the new pointer in addition to the ones it is handling.  

110.                             newTouchTarget.pointerIdBits |= idBitsToAssign;  

111.                             break;  

112.                         }  

113.   

114.                         resetCancelNextUpFlag(child);  

115.                         if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {  

116.                             // Child wants to receive touch within its bounds.  

117.                             mLastTouchDownTime = ev.getDownTime();  

118.                             mLastTouchDownIndex = childIndex;  

119.                             mLastTouchDownX = ev.getX();  

120.                             mLastTouchDownY = ev.getY();  

121.                             newTouchTarget = addTouchTarget(child, idBitsToAssign);  

122.                             alreadyDispatchedToNewTouchTarget = true;  

123.                             break;  

124.                         }  

125.                     }  

126.                 }  

127.   

128.                 if (newTouchTarget == null && mFirstTouchTarget != null) {  

129.                     // Did not find a child to receive the event.  

130.                     // Assign the pointer to the least recently added target.  

131.                     newTouchTarget = mFirstTouchTarget;  

132.                     while (newTouchTarget.next != null) {  

133.                         newTouchTarget = newTouchTarget.next;  

134.                     }  

135.                     newTouchTarget.pointerIdBits |= idBitsToAssign;  

136.                 }  

137.             }  

138.         }  

139.   

140.         // Dispatch to touch targets.  

141.         if (mFirstTouchTarget == null) {  

142.             // No touch targets so treat this as an ordinary view.  

143.             handled = dispatchTransformedTouchEvent(ev, canceled, null,  

144.                     TouchTarget.ALL_POINTER_IDS);  

145.         } else {  

146.             // Dispatch to touch targets, excluding the new touch target if we already  

147.             // dispatched to it.  Cancel touch targets if necessary.  

148.             TouchTarget predecessor = null;  

149.             TouchTarget target = mFirstTouchTarget;  

150.             while (target != null) {  

151.                 final TouchTarget next = target.next;  

152.                 if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {  

153.                     handled = true;  

154.                 } else {  

155.                     final boolean cancelChild = resetCancelNextUpFlag(target.child)  

156.                             || intercepted;  

157.                     if (dispatchTransformedTouchEvent(ev, cancelChild,  

158.                             target.child, target.pointerIdBits)) {  

159.                         handled = true;  

160.                     }  

161.                     if (DBG_MOTION) {  

162.                         Xlog.d(TAG, "dispatchTouchEvent middle 5: cancelChild = " + cancelChild  

163.                                 + ",mFirstTouchTarget = " + mFirstTouchTarget + ",target = "  

164.                                 + target + ",predecessor = " + predecessor + ",next = " + next  

165.                                 + ",this = " + this);  

166.                     }  

167.                     if (cancelChild) {  

168.                         if (predecessor == null) {  

169.                             mFirstTouchTarget = next;  

170.                         } else {  

171.                             predecessor.next = next;  

172.                         }  

173.                         target.recycle();  

174.                         target = next;  

175.                         continue;  

176.                     }  

177.                 }  

178.                 predecessor = target;  

179.                 target = next;  

180.             }  

181.         }  

182.   

183.         // Update list of touch targets for pointer up or cancel, if needed.  

184.         if (canceled  

185.                 || actionMasked == MotionEvent.ACTION_UP  

186.                 || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {  

187.             resetTouchState();  

188.         } else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {  

189.             final int actionIndex = ev.getActionIndex();  

190.             final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);  

191.             removePointersFromTouchTargets(idBitsToRemove);  

192.         }  

193.     }  

194.   

195.     if (DBG_MOTION) {  

196.         Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent end 4: handled = " + handled + ",mFirstTouchTarget = "  

197.                 + mFirstTouchTarget + ",this = " + this);  

198.     }  

199.   

200.     if (!handled && mInputEventConsistencyVerifier != null) {  

201.         mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);  

202.     }  

203.     return handled;  

204. }