在ViewRootImpl的setView方法中，用户的触摸按键消息是体现在窗体上的，而windowManagerService则是管理这些窗口，它一旦接收到用户对窗体的一些触摸按键消息，会进行相应的动作，这种动作是需要体现在具体的view上面，在Android中，一个具体的界面是由一个Activity呈现的，而Activity中则包含了一个window，此window中又包含了一个phoneWindow，这个phoneWindow才是真正意义上的窗口，它把一个框架布局进行了一定的包装，并提供了具体的窗口操作接口，phoneWindow中包含了一个DecorView，这个view才是包含整个Activity的ui，它将被attach到Activity主窗口中。所以说用户触摸按键的消息是由windowManagerService捕捉到然后交给phoneWindow中的DecorView进行相应的处理，而连接两者的桥梁则是一个ViewRoot类，ViewRoot类由windowManagerService创建，其内部有一个W类，这个W类是一个binder，负责WindowManagerService的ipc调用，W接收到windowManagerService发送过来的消息后，把消息传递给ViewRoot，进而传递给ActivityThread解析做出处理，
1、在ViewRootImpl.java类的setView方法中：
<span style="font-size:14px;"><span style="white-space:pre"> </span>res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, getHostVisibility(), mDisplay.getDisplayId(),mAttachInfo.mContentInsets, mInputChannel);</span>在这里把mWindow传递给了window，这个mWindow就是W类的一个实例
2、当具体的触摸按键消息发生后，会由ViewRootImpl类中WindowInputEventReceiver这个类的onInputEvent方法负责接收，其实也就是个回调。
<span style="font-size:14px;"><span style="white-space:pre"> </span>public void onInputEvent(InputEvent event) { <span style="white-space:pre"> </span> enqueueInputEvent(event, this, 0, true); <span style="white-space:pre"> </span>}</span> <span style="font-size:14px;">void enqueueInputEvent(InputEvent event, InputEventReceiver receiver, int flags, boolean processImmediately) { QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags); // Always enqueue the input event in order, regardless of its time stamp. // We do this because the application or the IME may inject key events // in response to touch events and we want to ensure that the injected keys // are processed in the order they were received and we cannot trust that // the time stamp of injected events are monotonic. QueuedInputEvent last = mFirstPendingInputEvent; if (last == null) { mFirstPendingInputEvent = q; } else { while (last.mNext != null) { last = last.mNext; } last.mNext = q; } if (processImmediately) { // 立即处理事件 doProcessInputEvents(); } else { // 将事件放到队列的最后 scheduleProcessInputEvents(); } }</span> 在enqueueInputEvent方法中，把event加入到队列的最后面，如果processImmediately为true，则直接调用doProcessInputEvents方法，否则scheduleProcessInputEvents被调用，这两个方法最后都调用了deliverInputEvent方法，用于分发输入事件。在这个方法中判断如果是按键事件，比如说back、home等，就会调用deliverKeyEvent分发事件，一些一般的移动事件调用deliverGenericMotionEvent方法。
<span style="font-size:14px;"> private void deliverInputEvent(QueuedInputEvent q) { Trace.traceBegin(Trace.TRACE_TAG_VIEW, "deliverInputEvent"); try { if (q.mEvent instanceof KeyEvent) { // 如果是按键事件，也就是back、home等按键 deliverKeyEvent(q); } else { // touch事件 final int source = q.mEvent.getSource(); if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) { deliverPointerEvent(q); } else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) { deliverTrackballEvent(q); } else { deliverGenericMotionEvent(q); } } } finally { Trace.traceEnd(Trace.TRACE_TAG_VIEW); } }</span>在deliverPointerEvent方法中，如果view对象不存在，或者没有被添加，则这个event不会被处理，直接finishInputEvent。接着判断action是否是MotionEvent.ACTION_DOWN，如果是，则表示触摸方式改变了，需要告诉windowManager在本地进行处理，因为每一次的按下操作都代表了一个新的event事件的到来。然后记录触摸的位置，这个位置就代表了应该是哪一个view来接收这个事件，然后直接调用mView.dispatchPointerEvent(event)来分发这个事件，如果这个事件被分发下去了，则结束事件。<span style="font-size:14px;"> private void deliverPointerEvent(QueuedInputEvent q) { final MotionEvent event = (MotionEvent)q.mEvent; final boolean isTouchEvent = event.isTouchEvent(); if (mInputEventConsistencyVerifier != null) { if (isTouchEvent) { mInputEventConsistencyVerifier.onTouchEvent(event, 0); } else { mInputEventConsistencyVerifier.onGenericMotionEvent(event, 0); } } // If there is no view, then the event will not be handled. if (mView == null || !mAdded) { // view对象为空，或者没有被添加，这个事件就不会被处理 finishInputEvent(q, false); return; } // Translate the pointer event for compatibility, if needed. if (mTranslator != null) { mTranslator.translateEventInScreenToAppWindow(event); } // Enter touch mode on down or scroll. final int action = event.getAction(); if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_SCROLL) { // 如果是MotionEvent.ACTION_DOWN // 如果是如果触摸方式改变，告诉wm，在本地进行处理 // 每一次的按下操作就是一个触摸事件的改变 ensureTouchMode(true); } // Offset the scroll position. if (mCurScrollY != 0) { event.offsetLocation(0, mCurScrollY); } if (MEASURE_LATENCY) { lt.sample("A Dispatching PointerEvents", System.nanoTime() - event.getEventTimeNano()); } // Remember the touch position for possible drag-initiation. // 有可能拖拽开始，记录触摸的位置 if (isTouchEvent) { mLastTouchPoint.x = event.getRawX(); mLastTouchPoint.y = event.getRawY(); } // Dispatch touch to view hierarchy. // 给view的层级上view分发事件 // DecorView继承FrameLayout也就间接继承了ViewGroup，View // DoverView---->Activity-->PhoneWindow--->DocerView---->ViewGroup boolean handled = mView.dispatchPointerEvent(event); if (MEASURE_LATENCY) { lt.sample("B Dispatched PointerEvents ", System.nanoTime() - event.getEventTimeNano()); } if (handled) { // 结束事件 finishInputEvent(q, true); return; } // Pointer event was unhandled. // 暗示事件已经被处理 finishInputEvent(q, false); </span>在DecorView中没有dispatchPointerEvent方法，所以调用的是View.java的dispatchPointerEvent方法中判断具体的是哪一类的事件，然后又调用了自身的dispatchTouchEvent。<span style="font-size:14px;">public final boolean dispatchPointerEvent(MotionEvent event) { if (event.isTouchEvent()) { // 如果是触摸事件 return dispatchTouchEvent(event); } else { // 如果是一般的移动事件 return dispatchGenericMotionEvent(event); } }</span>在DecorView.java的dispatchTouchEvent方法中，如果Activity不为空，并且没有被销毁，则调用Activity的dispatchTouchEvent方法，否则调用父类View的dispatchTouchEvent方法。
<span style="white-space:pre"> </span>@Override public boolean dispatchTouchEvent(MotionEvent ev) { // callback就是Activity本身 final Callback cb = getCallback(); // 如果Activity不为空，并且没有被销毁,则调用Activity的dispatchTouchEvent // 否则调用父类的dispatchTouchEvent return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev); }在Activity的dispatchTouchEvent方法中，调用的是PhoneWindow的superDispatchTouchEvent的方法去分发事件，如果到最后Activity中的所有的view都不去处理这个事件时，就有Activity的OnTouchEvent来处理。public boolean dispatchTouchEvent(MotionEvent ev) { if (ev.getAction() == MotionEvent.ACTION_DOWN) { // 在dispatch之前做一些操作，其实什么也没做 onUserInteraction(); } // 调用PhoneWindow中的superDispatchTouchEvent // PhoneWindow中superDispatchTouchEvent 直接调用了mDecor的superDispatchTouchEvent // mDecore的superDispatchTouchEvent方法中直接调用super.dispatchOnTouchEvent // 也就是开始进入了viewGroup中的dispatchOnTouchEvent方法 if (getWindow().superDispatchTouchEvent(ev)) { return true; } // 当Activity中所有的View都不处理Event的时候，就用由Activity的onTouchEvent()来处理 // 通知window关闭这个touch事件 return onTouchEvent(ev); } public boolean onTouchEvent(MotionEvent event) { if (mWindow.shouldCloseOnTouch(this, event)) { finish(); return true; } return false; } 在PhoneWindow的superDispatchTouchEvent中，调用了DecorView的superDispatchTouchEvent方法，进而调用了super.dispatchTouchEvent(event)方法，也就是进入了viewGroup中开始事件的分发。 @Override public boolean superDispatchTouchEvent(MotionEvent event) { return mDecor.superDispatchTouchEvent(event); } public boolean superDispatchTouchEvent(MotionEvent event) { return super.dispatchTouchEvent(event); } ViewGroup的dispatchTouchEvent中，处理如下，如果action是MotionEvent.ACTION_DOWN，则需要重置触摸的状态。继而判断是否拦截此事件，然后遍历所有的孩子以便找到一个可以接收此事件的孩子，如果child不存在TouchTarget中，则把事件分发给子view，这个寻找是根据view的区域来寻找的。如果childView没有消费掉此事件，则自己处理的事件，如果自己也没有处理，回溯至父view处理，否则viewGroup把事件一级一级的递归传递，如果child是一个viewGroup，则重复上述的步骤，如果是view，直接调用dispatchTouchEvent方法。 public boolean dispatchTouchEvent(MotionEvent ev) { if (mInputEventConsistencyVerifier != null) { mInputEventConsistencyVerifier.onTouchEvent(ev, 1); } boolean handled = false; if (onFilterTouchEventForSecurity(ev)) { final int action = ev.getAction(); final int actionMasked = action & MotionEvent.ACTION_MASK; // Handle an initial down. if (actionMasked == MotionEvent.ACTION_DOWN) { // Throw away all previous state when starting a new touch gesture. // The framework may have dropped the up or cancel event for the previous gesture // due to an app switch, ANR, or some other state change. // ACTION_DOWN意味着touch事件的改变，所以需要把之前的TouchTargets和TouchState都clear掉，mFirstTouchTarget = null cancelAndClearTouchTargets(ev); // 重置触摸的状态 resetTouchState(); } // Check for interception. final boolean intercepted; if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) { final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0; if (!disallowIntercept) { // 拦截事件，默认返回false，表示不拦截，如果拦截了就不继续往下面执行了 intercepted = onInterceptTouchEvent(ev); ev.setAction(action); // restore action in case it was changed } else { intercepted = false; } } else { // There are no touch targets and this action is not an initial down // so this view group continues to intercept touches. intercepted = true; } // Check for cancelation. final boolean canceled = resetCancelNextUpFlag(this) || actionMasked == MotionEvent.ACTION_CANCEL; // Update list of touch targets for pointer down, if needed. final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0; TouchTarget newTouchTarget = null; boolean alreadyDispatchedToNewTouchTarget = false; if (!canceled && !intercepted) { if (actionMasked == MotionEvent.ACTION_DOWN || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN) || actionMasked == MotionEvent.ACTION_HOVER_MOVE) { final int actionIndex = ev.getActionIndex(); // always 0 for down final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex) : TouchTarget.ALL_POINTER_IDS; // Clean up earlier touch targets for this pointer id in case they // have become out of sync. removePointersFromTouchTargets(idBitsToAssign); final int childrenCount = mChildrenCount; if (childrenCount != 0) { // Find a child that can receive the event. // Scan children from front to back. // 遍历所有的孩子，以便找到一个可以接收这个事件的孩子 // 某个区域内的孩子 final View[] children = mChildren; final float x = ev.getX(actionIndex); final float y = ev.getY(actionIndex); final boolean customOrder = isChildrenDrawingOrderEnabled(); for (int i = childrenCount - 1; i >= 0; i--) { final int childIndex = customOrder ? getChildDrawingOrder(childrenCount, i) : i; final View child = children[childIndex]; if (!canViewReceivePointerEvents(child) || !isTransformedTouchPointInView(x, y, child, null)) { continue; } // 判断child是否在TouchTarget中 newTouchTarget = getTouchTarget(child); if (newTouchTarget != null) { // 存在 // Child is already receiving touch within its bounds. // Give it the new pointer in addition to the ones it is handling. newTouchTarget.pointerIdBits |= idBitsToAssign; break; } resetCancelNextUpFlag(child); // child不存在TouchTarget中，则调用dispatchTransformedTouchEvent // 把event分发给子view，这里并不是做处理，应该就是找到touch区域 if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { // Child wants to receive touch within its bounds. mLastTouchDownTime = ev.getDownTime(); mLastTouchDownIndex = childIndex; mLastTouchDownX = ev.getX(); mLastTouchDownY = ev.getY(); newTouchTarget = addTouchTarget(child, idBitsToAssign); alreadyDispatchedToNewTouchTarget = true; break; } } } if (newTouchTarget == null && mFirstTouchTarget != null) { // Did not find a child to receive the event. // Assign the pointer to the least recently added target. newTouchTarget = mFirstTouchTarget; while (newTouchTarget.next != null) { newTouchTarget = newTouchTarget.next; } newTouchTarget.pointerIdBits |= idBitsToAssign; } } } // Dispatch to touch targets. if (mFirstTouchTarget == null) { // mFirstTouchTarget 为空，表示childview没有将此事件消费掉，则自己处理这个event // 如果viewGroup自己也没有处理，则回溯到父view进行处理 // No touch targets so treat this as an ordinary view. handled = dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS); } else { // Dispatch to touch targets, excluding the new touch target if we already // dispatched to it. Cancel touch targets if necessary. TouchTarget predecessor = null; TouchTarget target = mFirstTouchTarget; while (target != null) { final TouchTarget next = target.next; if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) { handled = true; } else { final boolean cancelChild = resetCancelNextUpFlag(target.child) || intercepted; // viewGroup把事件递归传递，如果child是一个gourp，则重复上述步骤 // 如果是view,则直接调用dispatchTouchEvent方法 if (dispatchTransformedTouchEvent(ev, cancelChild, target.child, target.pointerIdBits)) { handled = true; } if (cancelChild) { if (predecessor == null) { mFirstTouchTarget = next; } else { predecessor.next = next; } target.recycle(); target = next; continue; } } predecessor = target; target = next; } } // Update list of touch targets for pointer up or cancel, if needed. if (canceled || actionMasked == MotionEvent.ACTION_UP || actionMasked == MotionEvent.ACTION_HOVER_MOVE) { resetTouchState(); } else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) { final int actionIndex = ev.getActionIndex(); final int idBitsToRemove = 1 << ev.getPointerId(actionIndex); removePointersFromTouchTargets(idBitsToRemove); } } if (!handled && mInputEventConsistencyVerifier != null) { mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1); } return handled; }在View.java中的 dispatchTouchEvent方法中，如果已经注册了listener监听器并且是enable的，并且监听器的onTouch返回true，则onTouchEvent不会被调用。
public boolean dispatchTouchEvent(MotionEvent event) { if (mInputEventConsistencyVerifier != null) { mInputEventConsistencyVerifier.onTouchEvent(event, 0); } if (onFilterTouchEventForSecurity(event)) { //noinspection SimplifiableIfStatement ListenerInfo li = mListenerInfo; if (li != null && li.mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED && li.mOnTouchListener.onTouch(this, event)) { // 要想执行onTouchEvent方法上述三个条件只要一个不满足就可以了 // return true; } if (onTouchEvent(event)) { return true; } // 如果所有的View都不处理TouchEvent，最后由Activity来处理 } if (mInputEventConsistencyVerifier != null) { mInputEventConsistencyVerifier.onUnhandledEvent(event, 0); } return false; }如果Activity中所有的view都不处理这个事件，则由Activity自己处理
public boolean onTouchEvent(MotionEvent event) { if (mWindow.shouldCloseOnTouch(this, event)) { finish(); return true; } return false; }版权声明：本文为博主原创文章，未经博主允许不得转载。