天天记录 - Android Touch Event接收并传递给Activity

    代码执行堆栈

ViewRootImpl. dispatchMotion

ViewRootImpl. dispatchPointer   (sendMessage)

ViewRootImpl. handleMessage

     @Override
    public void handleMessage(Message msg) {
         ......
          case DISPATCH_POINTER:
            deliverPointerEvent((MotionEvent) msg.obj, msg.arg1 != 0);
         ......
     }

ViewRootImpl. deliverPointerEvent

    private void deliverPointerEvent(MotionEvent event, boolean sendDone) {
        if (ViewDebug.DEBUG_LATENCY) {
            mInputEventDeliverTimeNanos = System.nanoTime();
        }

        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) {
            finishMotionEvent(event, sendDone, 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.
          // 派发Touch Event
        boolean handled = mView.dispatchPointerEvent(event);
        if (MEASURE_LATENCY) {
            lt.sample("B Dispatched PointerEvents ", System.nanoTime() - event.getEventTimeNano());
        }
        if (handled) {
            finishMotionEvent(event, sendDone, true);
            return;
        }

        // Pointer event was unhandled.
        finishMotionEvent(event, sendDone, false);
    }

mView由PhoneWindow.DecorView实现，即执行PhoneWindow.DecorView. dispatchPointerEvent

     @Override
     public boolean dispatchTouchEvent(MotionEvent ev) {
          final Callback cb = getCallback();
          // cb != null cb就是拥有这个PhoneWindow的Activity
          //
          return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev)
                    : super.dispatchTouchEvent(ev);
     }

Callback就是Activity，通过分析获知以上判断 执行cb.dispatchTouchEvent即Activity.dispatchTouchEvent

    /**
     * Called to process touch screen events.  You can override this to
     * intercept all touch screen events before they are dispatched to the
     * window.  Be sure to call this implementation for touch screen events
     * that should be handled normally.
     *
     * @param ev The touch screen event.
     *
     * @return boolean Return true if this event was consumed.
     */
    public boolean dispatchTouchEvent(MotionEvent ev) {
        if (ev.getAction() == MotionEvent.ACTION_DOWN) {
            onUserInteraction();
        }
        if (getWindow().superDispatchTouchEvent(ev)) {
            return true;
        }
        return onTouchEvent(ev);
    }

接着执行  PhoneWindow.superDispatchTouchEvent

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

执行 PhoneWindow.DecorView.superDispatchTouchEvent

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

ViewGroup.dispatchTouchEvent 通过UI树，向下传递Touch Event

 Activity.onTouchEvent

     /**
     * Called when a touch screen event was not handled by any of the views
     * under it.  This is most useful to process touch events that happen
     * outside of your window bounds, where there is no view to receive it.
     *
     * @param event The touch screen event being processed.
     *
     * @return Return true if you have consumed the event, false if you haven't.
     * The default implementation always returns false.
     */
    public boolean onTouchEvent(MotionEvent event) {
        if (mWindow.shouldCloseOnTouch(this, event)) {
            finish();
            return true;
        }
       
        return false;
    }