Android touch事件传输过程
一、先看看整理流程图：
二、事件从Framework层如何传到UI进程
实际上就是实际从 WindowManagerService 传递到ViewRootImpl层。
我们在ViewRootImpl 可以看到这几个属性：
InputChannel mInputChannel; //输入事件channel
InputQueue.Callback mInputQueueCallback; //队列回掉
InputQueue mInputQueue; //输入队列
我们在setView方法中, 将ViewRootImpl的inputChannel对象交给了WindowManagerService
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mInputChannel);
在WindowManagerService#addWindow方法中将channel与nativeChannel关联上
public int addWindow(Session session, IWindow client, int seq,
WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
InputChannel outInputChannel) {
...
final boolean openInputChannels = (outInputChannel != null
&& (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0);
if (openInputChannels) {
win.openInputChannel(outInputChannel);
}
....
在看看win.openInputChannel方法
void openInputChannel(InputChannel outInputChannel) {
....
String name = getName();
InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);
mInputChannel = inputChannels[0];
mClientChannel = inputChannels[1];
mInputWindowHandle.inputChannel = inputChannels[0];
if (outInputChannel != null) {
mClientChannel.transferTo(outInputChannel);
mClientChannel.dispose();
mClientChannel = null;
} else {
// If the window died visible, we setup a dummy input channel, so that taps
// can still detected by input monitor channel, and we can relaunch the app.
// Create dummy event receiver that simply reports all events as handled.
mDeadWindowEventReceiver = new DeadWindowEventReceiver(mClientChannel);
}
//最终将输入channel和inputManager关联了。最终事件就传到mInputWindowHandle，
// mInputWindowHandle 和 outInputChannel 是配对的，可以理解为mInputWindowHandle接收到事件后
// 同时通知传递给了outInputChannel， 也就是 ViewRootImpl的InputChannel
mService.mInputManager.registerInputChannel(mInputChannel, mInputWindowHandle);
}
再Ui进程，ViewRootImpl#WindowInputEventReceiver
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
Looper.myLooper());
}
final class WindowInputEventReceiver extends InputEventReceiver {
public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
super(inputChannel, looper);
}
public void onInputEvent(InputEvent event) {
enqueueInputEvent(event, this, 0, true); //得到input事件，并且放入队列
}
...
}
public InputEventReceiver(InputChannel inputChannel, Looper looper) {
if (inputChannel == null) {
throw new IllegalArgumentException("inputChannel must not be null");
}
if (looper == null) {
throw new IllegalArgumentException("looper must not be null");
}
mInputChannel = inputChannel;
mMessageQueue = looper.getQueue();
//native层不断从inputChannel中传递事件到MessageQueue中，得到从WindowManagerService中的事件
mReceiverPtr = nativeInit(new WeakReference<InputEventReceiver>(this),
inputChannel, mMessageQueue);
mCloseGuard.open("dispose");
}
void enqueueInputEvent(InputEvent event,
InputEventReceiver receiver, int flags, boolean processImmediately) {
adjustInputEventForCompatibility(event);
QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
QueuedInputEvent last = mPendingInputEventTail;
...
doProcessInputEvents(); //处理分发event。最终调用到了mView.dispatchPointerEvent
}
三、UI层的传递
ViewRootImpl 内部类接收到来自WindowManagerService的事件之后。通过调用view.dispatchPointerEvent 向下分发事件。
View#dispatchPointerEvent
public final boolean dispatchPointerEvent(MotionEvent event) {
if (event.isTouchEvent()) {
return dispatchTouchEvent(event);
} else {
return dispatchGenericMotionEvent(event); //这个是什么shi
}
}
ViewRootImpl 中的view其实就是DecorView。让我们看看DecorView的dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent ev) {
final Window.Callback cb = mWindow.getCallback(); // 这里其实是activity#attach方法中设置，callback在activity中实现
return cb != null && !mWindow.isDestroyed() && mFeatureId < 0
? cb.dispatchTouchEvent(ev) : super.dispatchTouchEvent(ev);
}
mWindow.getCallback()其实就是activity 中实现了这个接口。好的，让我们看看activity#dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction(); // 空实现，表示用户开始交互
}
if (getWindow().superDispatchTouchEvent(ev)) {
// 若getWindow().superDispatchTouchEvent(ev)的返回true
// 则Activity.dispatchTouchEvent（）就返回true，则方法结束。即 ：该点击事件停止往下传递 & 事件传递过程结束
// 否则：继续往下调用Activity.onTouchEvent
return true;
}
return onTouchEvent(ev);
}
让我们分析下getWindow().superDispatchTouchEvent。 其实就是调用的PhoneWindow#superDispatchTouchEvent
public boolean superDispatchTouchEvent(MotionEvent event) {
return mDecor.superDispatchTouchEvent(event); //DecorView
}
//DecorView#superDispatchTouchEvent
public boolean superDispatchTouchEvent(MotionEvent event) {
return super.dispatchTouchEvent(event);
// 调用父类的方法 = ViewGroup的dispatchTouchEvent()
// 即 将事件传递到ViewGroup去处理，详细请看ViewGroup的事件分发机制
}
好的，让我们继续往下看Activity#onTouchEvent
// 当一个点击事件未被Activity下任何一个View接收 / 处理时
public boolean onTouchEvent(MotionEvent event) {
if (mWindow.shouldCloseOnTouch(this, event)) {
finish();
return true;
}
return false; // 返回，事件分发结束，
}
//Window#shouldCloseOnTouch 按下事件，不再context边界范围内 就返回true
public boolean shouldCloseOnTouch(Context context, MotionEvent event) {
if (mCloseOnTouchOutside && event.getAction() == MotionEvent.ACTION_DOWN
&& isOutOfBounds(context, event) && peekDecorView() != null) {
return true;
}
return false;
}
小结：以下是touchEvent传递到Activity#dispatchTouchEvent这里的流程图。
在流程图中，getWindow.superDispatchTouchEvent最终实现是在 ViewGroup#ViewGroup的dispatchTouchEvent。
好了，解下来分析ViewGroup#ViewGroup的dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent ev) {
....
boolean handled = false;
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) { //如果是down事件或者说，是down之后的事件比如up，需要判断是否拦截
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev); //判断是否拦截，若是button、或者在滚动条上 返回true
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; //如果不是DOWN事件，并且没有触摸目标。就拦截住
}
if (intercepted || mFirstTouchTarget != null) {
ev.setTargetAccessibilityFocus(false);
}
////如果没有被拦截，并且不是取消事件
if (!canceled && !intercepted) {
//，找到当前获取焦点的view
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
....
//先将ziView进行排序
final ArrayList<View> preorderedList = buildTouchDispatchChildList()
//依次判断子View是否处理当前事件
for (int i = childrenCount - 1; i >= 0; i--) {
....
if (childWithAccessibilityFocus != null) { //寻找当前焦点的子View，否则一直往下查找
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) { //判断当前View是否能处理触摸点
ev.setTargetAccessibilityFocus(false);
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;
}
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { //如果有子View处理事件
// Child wants to receive touch within its bounds.
mLastTouchDownTime = ev.getDownTime();
if (preorderedList != null) {
// childIndex points into presorted list, find original index
for (int j = 0; j < childrenCount; j++) {
if (children[childIndex] == mChildren[j]) {
mLastTouchDownIndex = j;
break;
}
}
} else {
mLastTouchDownIndex = childIndex;
}
mLastTouchDownX = ev.getX();
mLastTouchDownY = ev.getY();
newTouchTarget = addTouchTarget(child, idBitsToAssign); //mFirstTouchTarget 设置为当前处理的View
alreadyDispatchedToNewTouchTarget = true;
break;
}...
}
....
// Dispatch to touch targets.
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
//也就是说当intercept为true的时候，就当成是view使用，调用view的dispatch， 然后是ontouch。也即是在本层处理touch事件。
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
}
..
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
if (child == null) {
handled = super.dispatchTouchEvent(event); //调用View的dispatch，在本层被消耗掉
} else {
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
event.offsetLocation(offsetX, offsetY);
handled = child.dispatchTouchEvent(event); //调用子View的Dispatch，子view可能是View Group 还可以继续向下传递
event.offsetLocation(-offsetX, -offsetY);
}
return handled;
return handled;
}
小结下，此处ViewGroup#dispatchEvent处理事件流程
可以看到， 这里ViewGroup最终将事件传递给了View处理。
View#dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent event) {
// If the event should be handled by accessibility focus first.
if (event.isTargetAccessibilityFocus()) {
// We don't have focus or no virtual descendant has it, do not handle the event.
if (!isAccessibilityFocusedViewOrHost()) {
return false;
}
// We have focus and got the event, then use normal event dispatch.
event.setTargetAccessibilityFocus(false);
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
// 看，这里执行到OnTouch了
if (!result && onTouchEvent(event)) {
result = true;
}
}
.....
//View#onTouchEvent
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
if ((viewFlags & ENABLED_MASK) == DISABLED) {
if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
// A disabled view that is clickable still consumes the touch
// events, it just doesn't respond to them.
return (((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
}
if (mTouchDelegate != null) { // 设置了其他代理，代理响应处理
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
(viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) { //如果能够满足能够被点击、被长按、CONTEXT_CLICKABLE 就处理，并返回true
.... //处理各类事件
}
return true;
}
return false; //否则返回为false
}
Android事件分发总是先传递到ViewGroup、再传递到View