android事件处理涉及到的三个重要函数

事件分发：public boolean dispatchTouchEvent(MotionEvent ev)

由外部View接收，然后依次传递给其内层View

事件拦截：public boolean onInterceptTouchEvent(MotionEvent ev)

从最内View单元（事件源）开始依次向外层传递

事件响应：public boolean onTouchEvent(MotionEvent ev)

复杂性表现在：

可以控制每层事件是否继续传递（分发和拦截协同实现），以及事件的具体消费（事件分发也具有事件消费能力）。

三个函数所处位置

Activity 包含 dispatchTouchEvent 和 onTouchEvent方法（API 25）：

    /**
     * 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);
    }

    /**
     * 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;
    }

ViewGroup包含dispatchTouchEvent和onInterceptTouchEvent方法。

View包含 dispatchTouchEvent 和 onTouchEvent方法。

点击Button按钮时：

硬件触发

--> Activity示例(如LoginAcvtivity).dispatchTouchEvent --> Activity.dispatchTouchEvent

--> ViewGroup.dispatchTouchEvent --> ViewGroup.onInterceptTouchEvent

--> View.dispatchTouchEvent --> View.onTouchEvent

中间还有 DecorView.dispatchTouchEvent，PhoneView.superDispatchTouchEvent，DecorView.superDispatchTouchEvent被触发，因为他们在Activity和ViewGrounp之间。

image.png

参考：

Android View事件分发机制源码分析

Android事件分发机制源码解析

Android事件分发机制完全解析，带你从源码的角度彻底理解(上)

Android事件分发机制完全解析，带你从源码的角度彻底理解(下)