Touch事件分发

之前分析了界面显示流程,显示以后,界面将接收用户操作事件,本文将分析Touch事件分发机制。

1. 由Activity显示到界面流程分析中我们知道最后创建ViewRoot,ViewRoot的setView中注册了事件消息处理。

具体的注册流程和事件回调请看老罗消息处理机制分析

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public void setView(View view, WindowManager.LayoutParams attrs,
View panelParentView) {
synchronized (this) {
if (mView == null) {
mView = view;
mWindowAttributes.copyFrom(attrs);
attrs = mWindowAttributes;

mSoftInputMode = attrs.softInputMode;
mWindowAttributesChanged = true;
mAttachInfo.mRootView = view;
mAttachInfo.mScalingRequired = mTranslator != null;
mAttachInfo.mApplicationScale =
mTranslator == null ? 1.0f : mTranslator.applicationScale;
if (panelParentView != null) {
mAttachInfo.mPanelParentWindowToken
= panelParentView.getApplicationWindowToken();
}

requestLayout();
mInputChannel = new InputChannel();
try {
res = sWindowSession.add(mWindow, mWindowAttributes,
getHostVisibility(), mAttachInfo.mContentInsets,
mInputChannel);
} catch (RemoteException e) {

} finally {
if (restore) {
attrs.restore();
}
}

if (mInputQueueCallback != null) {

} else {
InputQueue.registerInputChannel(mInputChannel, mInputHandler,
Looper.myQueue());
}
}
}
}

InputQueue.registerInputChannel(mInputChannel, mInputHandler,Looper.myQueue()),注册接收mInputHandler。

2. new InputHandler()

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private final InputHandler mInputHandler = new InputHandler() {
public void handleKey(KeyEvent event, Runnable finishedCallback) {
startInputEvent(finishedCallback);
dispatchKey(event, true);
}

public void handleMotion(MotionEvent event, Runnable finishedCallback) {
startInputEvent(finishedCallback);
dispatchMotion(event, true);
}
};

3. ViewRoot.dispatchMotion

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private void dispatchMotion(MotionEvent event, boolean sendDone) {
int source = event.getSource();
if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
dispatchPointer(event, sendDone);
} else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
dispatchTrackball(event, sendDone);
} else {
// TODO
Log.v(TAG, "Dropping unsupported motion event (unimplemented): " + event);
if (sendDone) {
finishInputEvent();
}
}
}

4. ViewRoot.dispatchPointer

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private void dispatchPointer(MotionEvent event, boolean sendDone) {
Message msg = obtainMessage(DISPATCH_POINTER);
msg.obj = event;
msg.arg1 = sendDone ? 1 : 0;
sendMessageAtTime(msg, event.getEventTime());
}

ViewRoot本身是Handler对象。

5. ViewRoot.handleMessage

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@Override 
public void handleMessage(Message msg) {
switch (msg.what) {
case DISPATCH_POINTER: {
MotionEvent event = (MotionEvent) msg.obj;
try {
deliverPointerEvent(event);
} finally {
event.recycle();
if (msg.arg1 != 0) {
finishInputEvent();
}
if (LOCAL_LOGV || WATCH_POINTER) Log.i(TAG, "Done dispatching!");
}
} break;
}

6. ViewRoot.deliverPointerEvent

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private void deliverPointerEvent(MotionEvent event) {
if (mTranslator != null) {
mTranslator.translateEventInScreenToAppWindow(event);
}

boolean handled;
if (mView != null && mAdded) {

...

handled = mView.dispatchTouchEvent(event);
if (MEASURE_LATENCY) {
lt.sample("B Dispatched TouchEvents ", System.nanoTime() - event.getEventTimeNano());
}
if (!handled && isDown) {
int edgeSlop = mViewConfiguration.getScaledEdgeSlop();

....

if (edgeFlags != 0 && mView instanceof ViewGroup) {
View nearest = FocusFinder.getInstance().findNearestTouchable(
((ViewGroup) mView), x, y, direction, deltas);
if (nearest != null) {
event.offsetLocation(deltas[0], deltas[1]);
event.setEdgeFlags(0);
mView.dispatchTouchEvent(event);
}
}
}
}
}
这里mView在setView的方法中初始化,其实就是Window中的DecorView。

7. DecorView.dispatchTouchEvent

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public boolean dispatchKeyEvent(KeyEvent event) {
final int keyCode = event.getKeyCode();
final boolean isDown = event.getAction() == KeyEvent.ACTION_DOWN;

final Callback cb = getCallback();
final boolean handled = cb != null && mFeatureId < 0 ? cb.dispatchKeyEvent(event)
: super.dispatchKeyEvent(event);
if (handled) {
return true;
}
return isDown ? PhoneWindow.this.onKeyDown(mFeatureId, event.getKeyCode(), event)
: PhoneWindow.this.onKeyUp(mFeatureId, event.getKeyCode(), event);
}

这里的callback就是在activity的attach方法中设置的,其实就是Activity。

8. Activity.dispatchTouchEvent

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public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}

9. PhoneWindow.superDispatchTouchEvent

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@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
return mDecor.superDispatchTouchEvent(event);
}

10. DecorView.superDispatchTouchEvent

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public boolean superDispatchTouchEvent(MotionEvent event) {
return super.dispatchTouchEvent(event);
}

11. ViewGroup.dispatchTouchEvent

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@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (!onFilterTouchEventForSecurity(ev)) {
return false;
}

final int action = ev.getAction();
final float xf = ev.getX();
final float yf = ev.getY();
final float scrolledXFloat = xf + mScrollX;
final float scrolledYFloat = yf + mScrollY;
final Rect frame = mTempRect;

boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;

if (action == MotionEvent.ACTION_DOWN) {
if (mMotionTarget != null) {
// this is weird, we got a pen down, but we thought it was
// already down!
// XXX: We should probably send an ACTION_UP to the current
// target.
mMotionTarget = null;
}
// If we're disallowing intercept or if we're allowing and we didn't
// intercept
if (disallowIntercept || !onInterceptTouchEvent(ev)) {
// reset this event's action (just to protect ourselves)
ev.setAction(MotionEvent.ACTION_DOWN);
// We know we want to dispatch the event down, find a child
// who can handle it, start with the front-most child.
final int scrolledXInt = (int) scrolledXFloat;
final int scrolledYInt = (int) scrolledYFloat;
final View[] children = mChildren;
final int count = mChildrenCount;

for (int i = count - 1; i >= 0; i--) {
final View child = children[i];
if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE
|| child.getAnimation() != null) {
child.getHitRect(frame);
if (frame.contains(scrolledXInt, scrolledYInt)) {
// offset the event to the view's coordinate system
final float xc = scrolledXFloat - child.mLeft;
final float yc = scrolledYFloat - child.mTop;
ev.setLocation(xc, yc);
child.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
if (child.dispatchTouchEvent(ev)) {
// Event handled, we have a target now.
mMotionTarget = child;
return true;
}
// The event didn't get handled, try the next view.
// Don't reset the event's location, it's not
// necessary here.
}
}
}
}
}

boolean isUpOrCancel = (action == MotionEvent.ACTION_UP) ||
(action == MotionEvent.ACTION_CANCEL);

if (isUpOrCancel) {
// Note, we've already copied the previous state to our local
// variable, so this takes effect on the next event
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
}

// The event wasn't an ACTION_DOWN, dispatch it to our target if
// we have one.
final View target = mMotionTarget;
if (target == null) {
// We don't have a target, this means we're handling the
// event as a regular view.
ev.setLocation(xf, yf);
if ((mPrivateFlags & CANCEL_NEXT_UP_EVENT) != 0) {
ev.setAction(MotionEvent.ACTION_CANCEL);
mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
}
return super.dispatchTouchEvent(ev);
}

// if have a target, see if we're allowed to and want to intercept its
// events
if (!disallowIntercept && onInterceptTouchEvent(ev)) {
final float xc = scrolledXFloat - (float) target.mLeft;
final float yc = scrolledYFloat - (float) target.mTop;
mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
ev.setAction(MotionEvent.ACTION_CANCEL);
ev.setLocation(xc, yc);
if (!target.dispatchTouchEvent(ev)) {
// target didn't handle ACTION_CANCEL. not much we can do
// but they should have.
}
// clear the target
mMotionTarget = null;
// Don't dispatch this event to our own view, because we already
// saw it when intercepting; we just want to give the following
// event to the normal onTouchEvent().
return true;
}

if (isUpOrCancel) {
mMotionTarget = null;
}

// finally offset the event to the target's coordinate system and
// dispatch the event.
final float xc = scrolledXFloat - (float) target.mLeft;
final float yc = scrolledYFloat - (float) target.mTop;
ev.setLocation(xc, yc);

if ((target.mPrivateFlags & CANCEL_NEXT_UP_EVENT) != 0) {
ev.setAction(MotionEvent.ACTION_CANCEL);
target.mPrivateFlags &= ~CANCEL_NEXT_UP_EVENT;
mMotionTarget = null;
}

return target.dispatchTouchEvent(ev);
}

1)首先判断disallowIntercept,只有ViewGroup才可以中断touch事件传递。
2)onInterceptTouchEvent开发者自定义是否中断事件传递,默认为false。
3)for循环遍历子View,然后调用子View的dispatchTouchEvent,如果有子View消费事件使用mMotionTarget记录当前的子View。
4)这里可以看出,只有Down的时候消费了事件才可以接收接下来的事件。
5)如果没有子View消费事件或者ViewGroup中断事件传递则调用super.dispatchTouchEvent(ev),则是View.dispatchTouchEvent(ev)。

12. View.dispatchTouchEvent

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public boolean dispatchTouchEvent(MotionEvent event) {
if (!onFilterTouchEventForSecurity(event)) {
return false;
}

if (mOnTouchListener != null && (mViewFlags & ENABLED_MASK) == ENABLED &&
mOnTouchListener.onTouch(this, event)) {
return true;
}
return onTouchEvent(event);
}

这里如果设置自定义的mOnTouchListener,然后消费事件则直接返回true,否则调用onTouchEvent

13 View.onTouchEvent

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public boolean onTouchEvent(MotionEvent event) {
final int viewFlags = mViewFlags;

if ((viewFlags & ENABLED_MASK) == DISABLED) {
// 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));
}

if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}

if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {
switch (event.getAction()) {
case MotionEvent.ACTION_UP:
boolean prepressed = (mPrivateFlags & PREPRESSED) != 0;
if ((mPrivateFlags & PRESSED) != 0 || prepressed) {
// take focus if we don't have it already and we should in
// touch mode.
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}

if (!mHasPerformedLongPress) {
// This is a tap, so remove the longpress check
removeLongPressCallback();

// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
// Use a Runnable and post this rather than calling
// performClick directly. This lets other visual state
// of the view update before click actions start.
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
performClick();
}
}
}

if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}

}
break;

case MotionEvent.ACTION_DOWN:

break;

case MotionEvent.ACTION_CANCEL:

break;

case MotionEvent.ACTION_MOVE:

break;
}
return true;
}

return false;
}

如果View是CLICKABLE,直接消费事件(Button就是CLICKABLE)

touch消息处理流程图