Android View事件分发机制

Android View 事件分发机制

// Activity.dispatchTouchEvent()
public boolean dispatchTouchEvent(MotionEvent ev) {
        if (getWindow().superDispatchTouchEvent(ev)) {
            return true;
        }
        return onTouchEvent(ev);
}
// PhoneWindow.superDispatchTouchEvent()
public boolean superDispatchTouchEvent(MotionEvent event) {
        return mDecor.superDispatchTouchEvent(event);
}
// DecorView.superDispatchTouchEvent()
public boolean superDispatchTouchEvent(MotionEvent event) {
        return super.dispatchTouchEvent(event);
}
// ViewGroup.dispatchTouchEvent()
public boolean dispatchTouchEvent(MotionEvent ev) {
        if (actionMasked == MotionEvent.ACTION_DOWN) {
            resetTouchState();// 重置FLAG_DISALLOW_INTERCEPT
        }
        /**
        1、ViewGroup不拦截事件 -> mFirstTouchTarget != null
        2、ViewGroup拦截事件   -> mFirstTouchTarget == null
        3、ViewGroup拦截事件   -> ACTION_MOVE和ACTION_UP的onInterceptTouchEvent不执行
        4、ACTION_DOWN -> onInterceptTouchEvent必执行
        5、requestDisallowInterceptTouchEvent -> ViewGroup无法拦截非ACTION_DOWN事件
        */
        if (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != null) {
            disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
            if (!disallowIntercept) {
                intercepted = onInterceptTouchEvent(ev);
            } else {
                intercepted = false;
            }
        } else {
            intercepted = true;
        }
        if (!intercepted) {
            final View[] children = mChildren;
            for (int i = childrenCount - 1; i >= 0; i--) {
                View child = children[childIndex];
                // 子元素是否在播动画 || 点击事件坐标是否在子元素区域内
                if (!canViewReceivePointerEvents(child)
                        || !isTransformedTouchPointInView(x, y, child)) {
                    continue;
                }
                newTouchTarget = getTouchTarget(child);
                //  -> child.dispatchTouchEvent
                if (dispatchTransformedTouchEvent(ev, false, child)) {
                    // 设置mFirstTouchTarget
                    newTouchTarget = addTouchTarget(child);
                    break;
                }
            }
        }
        /**
        1、ViewGroup没有子元素；
        2、child.dispatchTouchEvent -> false : child.onTouchEvent -> false
        */
        if (mFirstTouchTarget == null) {
            // -> super.dispatchTouchEvent
            handled = dispatchTransformedTouchEvent(ev, canceled, null);
        } 
        return handled;
    }

    // View.dispatchTouchEvent()
    public boolean dispatchTouchEvent(MotionEvent event) {
        // mOnToucheListener.onTouch : true -> onTouchEvent不执行
        if (mOnTouchListener != null && mOnTouchListener.onTouch(this, event)) {
            result = true;
        }
        if (!result && onTouchEvent(event)) {
            result = true;
        }
        return result;
    }
    // View.onTouchEvent()
    public boolean onTouchEvent(MotionEvent event) {
        // if(CLICKABLE || LONG_CLICKABLE) : onTouchEvent -> true
        
        if ((viewFlags & ENABLED_MASK) == DISABLED) {
            return (((viewFlags & CLICKABLE) == CLICKABLE
                    || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE));
        }
        if (((viewFlags & CLICKABLE) == CLICKABLE ||
                (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {
            switch (action) {
                case MotionEvent.ACTION_UP:
                    performClick();// -> onClick()
                    break;
            }
            return true;
        }
        return false;
    }
    /**
    1、ViewGroup -> dispatchTouchEvent 、onInterceptTouchEvent
    2、View      -> dispatchTouchEvent 、onTouchEvent
    */
    public boolean dispatchTouchEvent(MotionEvent ev) {
        boolean consume = false;
        if(onInterceptTouchEvent(ev)){
            // super.dispatchTouchEvent -> View.dispatchTouchEvent -> onTouchEvent
            consume = onTouchEvent(ev);
        }else{
            // View || ViewGroup -> dispatchTouchEvent
            consume = child.dispatchTouchEvent(ev);
        }
        return consume;
    }