1.View的事件分发有两个重要的方法：`diapatchTouchEvent`和`touchEvent`

|---View
|   |---boolean dispatchTouchEvent(MotionEvent event)
|   |--- boolean onTouchEvent(MotionEvent event)

1. dispatchTouchEvent

dispatchTouchEvent中final int actionMasked = event.getActionMasked();
ListenerInfo :将view所有的listener信息封装到一个对象中。
在该方法中有两个判断：

 ListenerInfo li = mListenerInfo;
            if (li != null && li.mOnTouchListener != null
                    && (mViewFlags & ENABLED_MASK) == ENABLED
                    && li.mOnTouchListener.onTouch(this, event)) {
                result = true;
            }

            if (!result && onTouchEvent(event)) {
                result = true;
            }

如果onTouchEvent或者是onTouchListenner是true的话，会消费此事件，同时，在这里也走了onTouchEvent

2. boolean onTouchEvent

MotionEvent.ACTION_UP:调用了PerformClick()

三个问题：

1. 在activity中调用了

 mTouchView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.e("TAG", "onTouch: " + event.getAction());
                return false;
            }
        });
        mTouchView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.e("TAG", "onClick: " );
            }
        });
        
     /***********TabLayout************/   
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.e("TAG", "onTouchEvent: "+event.getAction());
        return super.onTouchEvent(event);
    }

执行顺序：

2. 如果是Tablyout中直接return ture呢？

不执行onClick,因为onClick在View.OntouchEvent中的ACTION_UP中，若直接return true 就不会走super中的方法。

3. 如果是dispatchEvent return true呢？

什么都不执行

分发流程

super.dispatchEvent->ListenerInfo->super.onTouchEvent(event)->ACTION_UP->performListener().

ViewGroup的事件分发：

首先是actionDown:

 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;
                }
            }

mFirstTouchTarget: 这个很重要,只有在第一次按下的时候才会调用disallowIntercept,如果之后想要改变效果的时候，这是一个坑。

|---ViewGroup
|   |---dispatchTouchEvent
|   |   |---onInterceptTouchEvent(ev)

有View会消耗时间的情况（比如点击，onTouchListener）

第一次按下进来(down)--->ViewGroup.dispatchTouchEvent--->ViewGroup.onInterceptTouchEvent(ev)-->view.dispatchEvent---(view的那一套)
第二次进来（move）ViewGroup.dispatchTouchEvent--->ViewGroup.onInterceptTouchEvent(ev)-->view.dispatchEvent---(view的那一套)
第三次（up））ViewGroup.dispatchTouchEvent--->ViewGroup.onInterceptTouchEvent(ev)-->view.dispatchEvent---(view的那一套)-->view.onClick

子View中没有消费事件的情况。只走一遍

第一次进来(down)ViewGroup.dispatchTouchEvent--->ViewGroup.onInterceptTouchEvent(ev)-->view.dispatchEvent---view.onTouch-->onTouchEvent

viewGroup的源码分析

actionDown

 /**
     * Clears all touch targets.
     */
    private void clearTouchTargets() {
        TouchTarget target = mFirstTouchTarget;
        if (target != null) {
            do {
                TouchTarget next = target.next;
                target.recycle();
                target = next;
            } while (target != null);
            mFirstTouchTarget = null; //清除target
        }
    }
<!--------------------------------------------------->
      if (!canceled && !intercepted) // intercepted 默认是没有拦截
      {
         if (newTouchTarget == null && childrenCount != 0) {
              for (int i = childrenCount - 1; i >= 0; i--) {//反序列的for循环 先拿最上面的layout
                if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
                }
              }
         }
      }


/**
     * Transforms a motion event into the coordinate space of a particular child view,
     * filters out irrelevant pointer ids, and overrides its action if necessary.
     * If child is null, assumes the MotionEvent will be sent to this ViewGroup instead.
     */
    private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
            View child, int desiredPointerIdBits) {
        final boolean handled;

        // Canceling motions is a special case.  We don't need to perform any transformations
        // or filtering.  The important part is the action, not the contents.
        final int oldAction = event.getAction();
        if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
            event.setAction(MotionEvent.ACTION_CANCEL);
            if (child == null) {
                handled = super.dispatchTouchEvent(event);
            } else {
                handled = child.dispatchTouchEvent(event);
            }
            event.setAction(oldAction);
            return handled;
        }

        // Calculate the number of pointers to deliver.
        final int oldPointerIdBits = event.getPointerIdBits();
        final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;

        // If for some reason we ended up in an inconsistent state where it looks like we
        // might produce a motion event with no pointers in it, then drop the event.
        if (newPointerIdBits == 0) {
            return false;
        }

        // 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;
    }

View的事件分发

1.View的事件分发有两个重要的方法：diapatchTouchEvent和touchEvent