Android4.4 Input模块笔记

浏览数：26 / 时间：2015年06月11日

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。

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public final boolean dispatchPointerEvent(MotionEvent event) {
if (event.isTouchEvent()) {
return dispatchTouchEvent(event);
} else {
return dispatchGenericMotionEvent(event);
}
}

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

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@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
final Callback cb = getCallback();
return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev)
: super.dispatchTouchEvent(ev);
}

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()

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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;
}
newTouchTarget = getTouchTarget(child);
if (newTouchTarget != null) {
// 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);
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;
}

具体的分发规则可自行研究代码。

ViewGroup.dispatchTouchEvent()函数分析

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@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
}
if (DBG_MOTION || DBG_TOUCH) {
Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent 1: ev = " + ev + ",mFirstTouchTarget = "
+ mFirstTouchTarget + ",this = " + this);
}
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.
cancelAndClearTouchTargets(ev);
resetTouchState();
}
// Check for interception.
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
/// M : add log to help debugging
if (intercepted == true) {
if (DBG_TOUCH) {
Xlog.d(TAG, "Touch event was intercepted event = " + ev + ",this = " + this);
}
}
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;
if (DBG_MOTION) {
Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent 2: actionMasked = " + actionMasked
+ ",intercepted = " + intercepted + ",canceled = " + canceled + ",split = "
+ split + ",mChildrenCount = " + mChildrenCount + ",mFirstTouchTarget = "
+ mFirstTouchTarget + ",this = " + this);
}
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 (newTouchTarget == null && childrenCount != 0) {
final float x = ev.getX(actionIndex);
final float y = ev.getY(actionIndex);
// Find a child that can receive the event.
// Scan children from front to back.
final View[] children = mChildren;
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)) {
if (DBG_MOTION) {
Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent continue 6: i = "
+ i + ",count = " + childrenCount + ",child = " + child
+ ",this = " + this);
}
continue;
}
newTouchTarget = getTouchTarget(child);
if (DBG_MOTION) {
Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent to child 3: child = "
+ child + ",childrenCount = " + childrenCount + ",i = " + i
+ ",newTouchTarget = " + newTouchTarget + ",idBitsToAssign = "
+ idBitsToAssign + ",mFirstTouchTarget = " + mFirstTouchTarget
+ ",this = " + this);
}
if (newTouchTarget != null) {
// 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);
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) {
// 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;
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
if (DBG_MOTION) {
Xlog.d(TAG, "dispatchTouchEvent middle 5: cancelChild = " + cancelChild
+ ",mFirstTouchTarget = " + mFirstTouchTarget + ",target = "
+ target + ",predecessor = " + predecessor + ",next = " + next
+ ",this = " + this);
}
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 (DBG_MOTION) {
Xlog.d(TAG, "(ViewGroup)dispatchTouchEvent end 4: handled = " + handled + ",mFirstTouchTarget = "
+ mFirstTouchTarget + ",this = " + this);
}
if (!handled && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);
}
return handled;
}