Android(安卓)触摸消息处理

1. WindowInputEventReceiver.onInputEvent() ----ViewRootImpl.java

从InputDispatch中publish一个Eent事件后，会由WindowInputEventReceiver.onInputEvent作为回调函数被调用。

        @Override        public void onInputEvent(InputEvent event) {            enqueueInputEvent(event, this, 0, true);        }

1.2. ViewRootImpl.enqueueInputEvent()

把event作为一个QueuedInputEvent放到列表队列最后，如果processImmediately == true那么就直接执行doProcessInputEvents()去立即处理这个event事件，如果不是就调用scheduleProcessInputEvents把Eent通过hander放入到主线程的Looper中。

    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) {            doProcessInputEvents();        } else {            scheduleProcessInputEvents();        }    }

2. ViewRootImpl.deliverInputEvent()

最后都会调用deliverInputEvent去分发事件，如果是KeyEent就调用deliverKeyEent(),同理如果是Touch，Pointer Event就调用deliverPointerEvent。

    private void deliverInputEvent(QueuedInputEvent q) {        Trace.traceBegin(Trace.TRACE_TAG_VIEW, "deliverInputEvent");        try {            if (q.mEvent instanceof KeyEvent) {                deliverKeyEvent(q);            } else {                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);        }    }

2.1 ViewRootImpl.deliverPointerEvent()

1. 如果mView == null || !mAdded, 就直接调用fininshInputEvent去告诉InputDispatcher;

2. 如果是ActionDown就是通过ensureTouchMode(true)告诉WMS去设置对应WindowState的touch mode，并且调用ensureTouchModeLocally来handle the change

3. 如果是touchevent就是用mLastTouchPoint去记录此次的Point的Position用于possible drag-initiation

4. mView.dispatchPointerEvent(event); 通过DecorView去dispatchPointerEvent;

5. 无论Event是否被处理，都会调用finishInputEvent(q, true);去告诉InputDispatcher。

    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) {            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) {            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.        if (isTouchEvent) {            mLastTouchPoint.x = event.getRawX();            mLastTouchPoint.y = event.getRawY();        }        // Dispatch touch to view hierarchy.        boolean handled = mView.dispatchPointerEvent(event);        if (MEASURE_LATENCY) {            lt.sample("B Dispatched PointerEvents ", System.nanoTime() - event.getEventTimeNano());        }        if (handled) {            finishInputEvent(q, true);            return;        }        // Pointer event was unhandled.        finishInputEvent(q, false);    }

2.1.4 DecorView.dispatchPointerEvent

DecorView继承FrameLayout也就间接继承了ViewGroup，View。

1. 调用父类View的dispatchPointerEvent(), 然后去调用自己的dispatchTouchEvent;

2. dispatchTouchEvent中调用callback.dispatchTouchEvent，这里的Callback就是Activity对象。

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

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

2.1.4.2 Activity.dispatchtouchEvent

1. onUserInteraction(), 在dispatch之前做一些操作

2. getwindow().superDispatchtouchEvent就是调用PhoneWindow中的superDispatchTouchEvent。而PhoneWindow也是直接调用mDecorView的对应的方法。而DoverView的superDispatchTouchEvent方法中是去调用了父类ViewGroup的dispatchTouchEvent。

3. 当Activity中所有的View都不处理Event的时候，就用由Activity的onTouchEvent()来处理。

这里的调用顺序从DoverView---->Activity-->PhoneWindow--->DocerView---->ViewGroup

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

2.1.4.2.1 ViewGroupdispatchTouchEvent(MotionEvent ev)

1. 如果是Action_Down事件，那么把之前的TouchTargets和TouchState都clear掉，mFirstTouchTarget = null

2. onInterceptTouchEvent()，通过这个函数去告诉当前的View是否拦截掉这个Event，如果return就不会把这个event往下dispatch了

3. 如果不去Intercept当前的Event，就通过遍历自己的child views去找到处在Touch所在区域的view，找到之后通过getTouchTarget(View)去查找View是否在TouchTarget中了；如果不在，则调用dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)，把Event分发给child view。

4. 如果child没有消耗掉event事件，那么mFirstTouchTarget == null)，这时候就会调用handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS)自己去处理此次Event; 参数中child为null。

如果ViewGroup也没处理，就会以此回溯上去给父View处理。

    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.                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);                    ev.setAction(action); // restore action in case it was changed                } else {                    intercepted = false;                }            } else {                ... ...            }            // 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.                        final View[] children = mChildren;                        final float x = ev.getX(actionIndex);                        final float y = ev.getY(actionIndex);                        for (int i = childrenCount - 1; i >= 0; i--) {                            final View child = children[i];                            if (!canViewReceivePointerEvents(child)                                    || !isTransformedTouchPointInView(x, y, child, null)) {                                continue;                            }                            newTouchTarget = getTouchTarget(child);  //通过getTouchTarget去查找View是否在TouchTarget中了。                            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 = i;                                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 (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;    }

2.1.4.2.1.3 ViewGroup.dispatchTransformedTouchEvent()

1. 主要是调用child.dispatchTouchEvent(transformedEvent);把事件递归传下去，如果child还是一个ViewGroup那么步骤和上面有一样，如果是View就调用View.dispatchTouchEvent(MotionEvent event)

  private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,            View child, int desiredPointerIdBits) {        final boolean handled;         // Calculate the number of pointers to deliver.        final int oldPointerIdBits = event.getPointerIdBits();        final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;        // If the number of pointers is the same and we don't need to perform any fancy        // irreversible transformations, then we can reuse the motion event for this        // dispatch as long as we are careful to revert any changes we make.        // Otherwise we need to make a copy.        final MotionEvent transformedEvent;        if (newPointerIdBits == oldPointerIdBits) {            if (child == null || child.hasIdentityMatrix()) {                if (child == null) {                    handled = super.dispatchTouchEvent(event);                } else {                    final float offsetX = mScrollX - child.mLeft;                    final float offsetY = mScrollY - child.mTop;                    event.offsetLocation(offsetX, offsetY);                    handled = child.dispatchTouchEvent(event);                    event.offsetLocation(-offsetX, -offsetY);                }                return handled;            }            transformedEvent = MotionEvent.obtain(event);        } else {            transformedEvent = event.split(newPointerIdBits);        }        // Perform any necessary transformations and dispatch.        if (child == null) {            handled = super.dispatchTouchEvent(transformedEvent);        } else {            final float offsetX = mScrollX - child.mLeft;            final float offsetY = mScrollY - child.mTop;            transformedEvent.offsetLocation(offsetX, offsetY);            if (! child.hasIdentityMatrix()) {                transformedEvent.transform(child.getInverseMatrix());            }            handled = child.dispatchTouchEvent(transformedEvent);        }        // Done.        transformedEvent.recycle();        return handled;    }

2.1.4.2.1.3.1View.dispatchTouchEvent(MotionEvent event)

1. 如果有TouchListener就去调用注册过的TouchListener的回调函数onTouch事件并直接返回。这就是为什么我们想接收一个touch event的时候只要写一个listener的原故。

2. 如果没有TouchListener，则调用默认的onTouchEvent(event)事件

    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)) {                return true;            }            if (onTouchEvent(event)) {                return true;            }        }        if (mInputEventConsistencyVerifier != null) {            mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);        }        return false;    }

2.1.4.2.1.4 Activity.onTouchEvent(MotionEvent event)

如果所有的View都不处理TouchEvent，最后由Activity来处理。

判断一下mWindow是否因此此Event要close掉，如果不close，就return false。

最后调用FinishInputEvent(false), 返回这个没有处理的Event。

    public boolean onTouchEvent(MotionEvent event) {        if (mWindow.shouldCloseOnTouch(this, event)) {            finish();            return true;        }                return false;    }

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