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

   從InputDispatch中publish一個Eent事件後，會由WindowInputEventReceiver.onInputEvent作為回撥函式被呼叫。

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

1.2.   ViewRootImpl.enqueueInputEvent()

    把event作為一個QueuedInputEvent放到列表佇列最後，如果processImmediately == true那麼就直接執行doProcessInputEvents()去立即處理這個event事件，如果不是就呼叫scheduleProcessInputEvents把Eent通過hander放入到主執行緒的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()

     最後都會呼叫deliverInputEvent去分發事件，如果是KeyEent就呼叫deliverKeyEent(),同理如果是Touch，Pointer Event就呼叫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, 就直接呼叫fininshInputEvent去告訴InputDispatcher;

    2. 如果是ActionDown就是通過ensureTouchMode(true)告訴WMS去設定對應WindowState的touch mode，並且呼叫ensureTouchModeLocally來handle the change

    3. 如果是touchevent就是用mLastTouchPoint去記錄此次的Point的Position用於possible drag-initiation

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

    5. 無論Event是否被處理，都會呼叫finishInputEvent(q, true);去告訴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繼承FrameLayout也就間接繼承了ViewGroup，View。

    1. 呼叫父類View的dispatchPointerEvent(), 然後去呼叫自己的dispatchTouchEvent;

    2. dispatchTouchEvent中呼叫callback.dispatchTouchEvent，這裡的Callback就是Activity物件。

    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就是呼叫PhoneWindow中的superDispatchTouchEvent。而PhoneWindow也是直接呼叫mDecorView的對應的方法。而DoverView的superDispatchTouchEvent方法中是去呼叫了父類ViewGroup的dispatchTouchEvent。

       3. 當Activity中所有的View都不處理Event的時候，就用由Activity的onTouchEvent()來處理。

        這裡的呼叫順序從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，那麼把之前的TouchTargets和TouchState都clear掉，mFirstTouchTarget = null

     2. onInterceptTouchEvent()，通過這個函式去告訴當前的View是否攔截掉這個Event，如果return就不會把這個event往下dispatch了

     3. 如果不去Intercept當前的Event，就通過遍歷自己的child views去找到處在Touch所在區域的view，找到之後通過getTouchTarget(View)去查詢View是否在TouchTarget中了；如果不在，則呼叫dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)，把Event分發給child view。

     4. 如果child沒有消耗掉event事件，那麼mFirstTouchTarget == null)，這時候就會呼叫handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS)自己去處理此次Event; 引數中child為null。

        如果ViewGroup也沒處理，就會以此回溯上去給父View處理。

    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);  //通過getTouchTarget去查詢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. 主要是呼叫child.dispatchTouchEvent(transformedEvent);把事件遞迴傳下去，如果child還是一個ViewGroup那麼步驟和上面有一樣，如果是View就呼叫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就去呼叫註冊過的TouchListener的回撥函式onTouch事件並直接返回。這就是為什麼我們想接收一個touch event的時候只要寫一個listener的原故。

     2. 如果沒有TouchListener，則呼叫預設的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都不處理TouchEvent，最後由Activity來處理。

  判斷一下mWindow是否因此此Event要close掉，如果不close，就return false。

 最後呼叫FinishInputEvent(false), 返回這個沒有處理的Event。

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