Android事件分发简单介绍

简单的讨论下关于Android的事件分发，其实网上的介绍很多，但是每次看完我都记的很晕，而我也只想知道当不同的返回值事件走的流程，所以这也只为自己做个简单的记录
首先说一下关于事件分发ViewGroup和View对应的方法
ViewGroup：dispatchTouchEvent、onTouchEvent、onInterceptTouchEvent、
View：dispatchTouchEvent、onTouchEvent
再定义了两个类GroupTest继承于LinearLayout（ViewGroup）和ButtonTest继承于Buttom（View），界面布局：

    <com.mmf.ibinderdemo.GroupTestandroid:id="@+id/lyt_test"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><com.mmf.ibinderdemo.ButtonTestandroid:id="@+id/btn_test"android:layout_width="match_parent"android:layout_height="48dp"android:text="click"/></com.mmf.ibinderdemo.GroupTest>

一、事件拦截

onInterceptTouchEvent(MotionEvent ev)方法
从上面可以看出这个方法只有ViewGroup有，作用是拦截事件向下传递，啥意思呢，就是当你的ViewGroup中有子控件，而在onInterceptTouchEvent被拦截了，那么你的子控价就收不到touch事件,我们从代码中来看这个效果
在GroupTest复写事件分发的三个方法

  @Overridepublic boolean onInterceptTouchEvent(MotionEvent ev){super.onInterceptTouchEvent(ev);Log.e("Touch = ", "group onInterceptTouchEvent  "+ ev.getAction() );return true;}@Overridepublic boolean onTouchEvent(MotionEvent event) {Log.e("Touch = ", "group onTouchEvent  "+ event.getAction() );return  super.onTouchEvent(event);}@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {boolean dispatchTouch = super.dispatchTouchEvent(ev);Log.e("Touch = ", "group dispatchTouchEvent +   " +dispatchTouch +ev.getAction());return dispatchTouch;}

ButtonTest复写

    @Overridepublic boolean onTouchEvent(MotionEvent event) {Log.e("Touch = ", "chile touch");return super.onTouchEvent(event);}@Overridepublic boolean dispatchTouchEvent(MotionEvent event) {Log.e("Touch = ", "chile dispatchTouchEvent");return super.dispatchTouchEvent(event);}

当onInterceptTouchEvent返回true时查看运行结果

10-20 05:17:13.207 8138-8138/com.mmf.ibinderdemo E/Touch =: group onInterceptTouchEvent  0
10-20 05:17:13.208 8138-8138/com.mmf.ibinderdemo E/Touch =: group onTouchEvent  0
10-20 05:17:13.208 8138-8138/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true0
10-20 05:17:13.302 8138-8138/com.mmf.ibinderdemo E/Touch =: group onTouchEvent  1
10-20 05:17:13.302 8138-8138/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true1
10-20 05:17:13.303 8138-8138/com.mmf.ibinderdemo E/MainActivity: lyt_test: grouptrue

当onInterceptTouchEvent返回false时查看运行结果

10-20 05:28:46.053 8362-8362/com.mmf.ibinderdemo E/Touch =: group onInterceptTouchEvent  0
10-20 05:28:46.053 8362-8362/com.mmf.ibinderdemo E/Touch =: chile dispatchTouchEvent
10-20 05:28:46.053 8362-8362/com.mmf.ibinderdemo E/Touch =: chile onTouchEvent
10-20 05:28:46.053 8362-8362/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true0
10-20 05:28:46.183 8362-8362/com.mmf.ibinderdemo E/Touch =: group onInterceptTouchEvent  1
10-20 05:28:46.183 8362-8362/com.mmf.ibinderdemo E/Touch =: chile dispatchTouchEvent
10-20 05:28:46.183 8362-8362/com.mmf.ibinderdemo E/Touch =: chile onTouchEvent
10-20 05:28:46.183 8362-8362/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true1
10-20 05:28:46.185 8362-8362/com.mmf.ibinderdemo E/MainActivity: btn_test: chiletrue

从以上结果可以看出当onInterceptTouchEvent返回true时会拦截事件的分发，子view接收不到事件，不执行onTouchEvent事件
如果返回 false，则表示不会拦截该事件，事件会被传递到子 View 上，执行onTouchEvent事件

二、事件消费

onTouchEvent(MotionEvent ev)这个方法就是用来处理具体点击事件的，它是在dispatchTouchEvent方法中调用
它的返回值表示是否消费当前事件，也就是是否响应当前事件，具体逻辑如下：
如果return true 则会接收并消费该事件。
如果return false，那么这个事件会向上传递，并由上层 View 的 onTouchEvent 来接收，如果传递到上面的 onTouchEvent 还是返回 false，这个事件无效，且接收不到下一次事件。什么意思呢，我们来看一下运行效果，将ButtonTest的onTouchEvent方法设置返回false，其他的保持原本状态

 @Overridepublic boolean onTouchEvent(MotionEvent event) {super.onTouchEvent(event);Log.e("Touch = ", "chile onTouchEvent = " + event.getAction());return false;}

执行结果

10-20 07:29:57.526 10182-10182/com.mmf.ibinderdemo E/Touch =: group onInterceptTouchEvent  0
10-20 07:29:57.526 10182-10182/com.mmf.ibinderdemo E/Touch =: chile dispatchTouchEvent
10-20 07:29:57.526 10182-10182/com.mmf.ibinderdemo E/Touch =: chile onTouchEvent = 0
10-20 07:29:57.526 10182-10182/com.mmf.ibinderdemo E/Touch =: group onTouchEvent  0
10-20 07:29:57.526 10182-10182/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true0
10-20 07:29:57.643 10182-10182/com.mmf.ibinderdemo E/Touch =: group onTouchEvent  1
10-20 07:29:57.643 10182-10182/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true1
10-20 07:29:57.643 10182-10182/com.mmf.ibinderdemo E/MainActivity: lyt_test: grouptrue

将ButtonTest的onTouchEvent方法设置返回true，其他的保持原本状态

 @Overridepublic boolean onTouchEvent(MotionEvent event) {super.onTouchEvent(event);Log.e("Touch = ", "chile onTouchEvent = " + event.getAction());return true;}

执行结果

10-20 07:28:25.021 10118-10118/? E/libprocessgroup: failed to make and chown /acct/uid_10066: Read-only file system
10-20 07:28:34.403 10118-10118/com.mmf.ibinderdemo E/Touch =: group onInterceptTouchEvent  0
10-20 07:28:34.403 10118-10118/com.mmf.ibinderdemo E/Touch =: chile dispatchTouchEvent
10-20 07:28:34.403 10118-10118/com.mmf.ibinderdemo E/Touch =: chile onTouchEvent = 0
10-20 07:28:34.403 10118-10118/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true0
10-20 07:28:34.530 10118-10118/com.mmf.ibinderdemo E/Touch =: group onInterceptTouchEvent  1
10-20 07:28:34.530 10118-10118/com.mmf.ibinderdemo E/Touch =: chile dispatchTouchEvent
10-20 07:28:34.530 10118-10118/com.mmf.ibinderdemo E/Touch =: chile onTouchEvent = 1
10-20 07:28:34.530 10118-10118/com.mmf.ibinderdemo E/Touch =: group dispatchTouchEvent +   true1
10-20 07:28:34.531 10118-10118/com.mmf.ibinderdemo E/MainActivity: btn_test: chiletrue

从结果上看，当返回false时，ButtonTest的onTouchEvent方式只执行了一次down的事件，别的事件都不再执行，且GroupTest消费了事件
当返回true时，表示该事件被这个ButtonTest消费了，GroupTest都没听调过onTouchEvent方法，因为事件被消费不再向上传递
ps：事件对应的值

MotionEvent.ACTION_DOWN = 0
MotionEvent.ACTION_MOVE = 2
MotionEvent.ACTION_UP = 1

三、事件分发

dispatchTouchEvent(MotionEvent ev)
竟然最后一个说事件分发，顺序跟事件步骤相反，因为我觉得如果事件拦截和事件消费大概流程懂了，事件分发就会更好理解