Android事件分发详细介绍
来源：互联网 发布：游戏原画网络班 编辑：程序博客网 时间：2024/05/30 07:14
由于最近本宝宝很是不开心，所以就觉得要拼命学习才可以。辣么大家就和我一起总结一下事件分发，可能很多人和我一样知道其一还不知道其二吧，或者还只是很模糊的知道。那么今天就去攻克它咯！在总结之前给大家说一个小的知识点吧，关于外部类使用内部类的内部类。（不知道内部类和外部类的一定要去百度学习一下哦）内部类也是外部类的一部分，所以在使用内部类的内部类的时候：内部类的内部类 a=内部类.内部类的内部类。不用new哦。好了，严肃点学习时间分发机制去啦。
鉴于手机屏幕的限制，所以android选择了分层的方式布局，这就引出了今天的主题－－事件分发
Android 中与 Touch 事件相关的方法包括：dispatchTouchEvent(MotionEvent ev)、onInterceptTouchEvent(MotionEvent ev)、onTouchEvent(MotionEvent ev)；能够响应这些方法的控件包括：ViewGroup 及其子类、Activity。方法与控件的对应关系如下表所示：
ViewGroup
Activity
public boolean dispatchTouchEvent(MotionEvent ev)事件分发
Yes Yes public boolean onInterceptTouchEvent(MotionEvent ev)
事件拦截
Yes No public boolean onTouchEvent(MotionEvent ev)事件响应
Yes Yes
从这张表中我们可以看到 ViewGroup 及其子类对与 Touch 事件相关的三个方法均能响应，而 Activity 对 onInterceptTouchEvent(MotionEvent ev) 也就是事件拦截不进行响应。
另外需要注意的是 View 对 dispatchTouchEvent(MotionEvent ev) 和 onInterceptTouchEvent(MotionEvent ev) 的响应的前提是可以向该 View 中添加子 View，如果当前的 View 已经是一个最小的单元 View（比如 TextView），那么就无法向这个最小 View 中添加子 View，也就无法向子 View 进行事件的分发和拦截，所以它没有dispatchTouchEvent(MotionEvent ev) 和 onInterceptTouchEvent(MotionEvent ev)，只有 onTouchEvent(MotionEvent ev)。
下面我们就来详细介绍一下这三个厉害的方法：
事件分发：
▐ 事件分发：public boolean dispatchTouchEvent(MotionEvent ev)
Touch 事件发生时 Activity 的 dispatchTouchEvent(MotionEvent ev) 方法会以隧道方式（从根元素依次往下传递直到最内层子元素或在中间某一元素中由于某一条件停止传递）将事件传递给最外层 View 的 dispatchTouchEvent(MotionEvent ev) 方法，并由该 View 的 dispatchTouchEvent(MotionEvent ev) 方法对事件进行分发。dispatchTouchEvent 的事件分发逻辑如下：
- 如果 return true，事件会分发给当前 View 并由 onTouchEvent(event)方法进行消费，同时事件会停止向下传递；
- 如果 return false，事件分发分为两种情况：
- 如果当前 View 获取的事件直接来自 Activity，则会将事件返回给 Activity 的 onTouchEvent 进行消费；
- 如果当前 View 获取的事件来自外层父控件，则会将事件返回给父 View 的 onTouchEvent 进行消费。
- 如果返回系统默认的 super.dispatchTouchEvent(ev)，事件会自动的分发给当前 View 的 onInterceptTouchEvent 方法。
▐ 事件拦截：public boolean onInterceptTouchEvent(MotionEvent ev)
在外层 View 的 dispatchTouchEvent(MotionEvent ev) 方法返回系统默认的 super.dispatchTouchEvent(ev) 情况下，事件会自动的分发给当前 View 的 onInterceptTouchEvent 方法。onInterceptTouchEvent 的事件拦截逻辑如下：
- 如果 onInterceptTouchEvent 返回 true，则表示将事件进行拦截，并将拦截到的事件交由当前 View 的 onTouchEvent 进行处理；
- 如果 onInterceptTouchEvent 返回 false，则表示将事件放行，当前 View 上的事件会被传递到子 View 上，再由子 View 的 dispatchTouchEvent 来开始这个事件的分发；
- 如果 onInterceptTouchEvent 返回 super.onInterceptTouchEvent(ev)，事件默认会被拦截，并将拦截到的事件交由当前 View 的 onTouchEvent 进行处理。
▐ 事件响应：public boolean onTouchEvent(MotionEvent ev)
在 dispatchTouchEvent 返回 super.dispatchTouchEvent(ev) 并且 onInterceptTouchEvent 返回 true 或返回 super.onInterceptTouchEvent(ev) 的情况下 onTouchEvent 会被调用。onTouchEvent 的事件响应逻辑如下：
- 如果事件传递到当前 View 的 onTouchEvent 方法，而该方法返回了 false，那么这个事件会从当前 View 向上传递，并且都是由上层 View 的 onTouchEvent 来接收，如果传递到上面的 onTouchEvent 也返回 false，这个事件就会“消失”，而且接收不到下一次事件。
- 如果返回了 true 则会接收并消费该事件。
- 如果返回 super.onTouchEvent(ev) 默认处理事件的逻辑和返回 false 时相同。
看了上面的描述，大家是不是有点小奔溃啊，就像读书那会看历史书一样，嘿嘿，老实说我也觉得刚刚开始看的时候有点晕。下面就从源码去找答案吧，到时候再看估计就会豁然开朗了。
先从简单的view的事件分发机制开始看，完了再看比较复杂的viewgroup吧！
view的事件分发机制源码
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">dispatchTouchEvent</span>(MotionEvent <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>) { boolean result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mInputEventConsistencyVerifier != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mInputEventConsistencyVerifier.onTouchEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>); } final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> actionMasked = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getActionMasked(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (actionMasked == MotionEvent.ACTION_DOWN) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Defensive cleanup for new gesture</span> stopNestedScroll(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (onFilterTouchEventForSecurity(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//noinspection SimplifiableIfStatement</span> ListenerInfo li = mListenerInfo; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (li != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && li.mOnTouchListener != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && (mViewFlags & ENABLED_MASK) == ENABLED && li.mOnTouchListener.onTouch(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) { result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!result && onTouchEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) { result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!result && mInputEventConsistencyVerifier != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mInputEventConsistencyVerifier.onUnhandledEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Clean up after nested scrolls if this is the end of a gesture;</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// also cancel it if we tried an ACTION_DOWN but we didn't want the rest</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// of the gesture.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (actionMasked == MotionEvent.ACTION_UP || actionMasked == MotionEvent.ACTION_CANCEL || (actionMasked == MotionEvent.ACTION_DOWN && !result)) { stopNestedScroll(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> result; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li></ul>我们来看核心代吧，请注意我的注释哦<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (onFilterTouchEventForSecurity(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) {//<span style="font-family: Simsun; font-size: 14px; line-height: 24px;">这个是事件安全过滤，与主题无关，就不去研究啦</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//noinspection SimplifiableIfStatement</span> ListenerInfo li = mListenerInfo;//重点就在这里，大家往下看 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (li != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && li.mOnTouchListener != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && (mViewFlags & ENABLED_MASK) == ENABLED && li.mOnTouchListener.onTouch(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) {//<span style="font-family: 'microsoft yahei'; font-size: 14px; line-height: 26px;">判断监听事件是否为空,是否有touch事件,</span></code><code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span style="font-family: 'microsoft yahei'; font-size: 14px; line-height: 26px;">判断当前控件是否为enable,回调onTouch()事件的返回值</span> result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!result && onTouchEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) { result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } } </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul><code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ListenerInfo getListenerInfo() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mListenerInfo != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mListenerInfo; } mListenerInfo = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ListenerInfo(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> mListenerInfo; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>从以上这段代码会看出mListenerInfo一定会被赋值,当然限定于ListenerInfo有的监听事件,监听事件不为空时,监听事件就存在onTouchListener,第三个条件基本都满足,Android控件默认的情况下都是enable,除非你手动设置,第四个条件,如果回调的onTouch()事件返回的为true,dispatchTouchEvent(event)直接返回true,否则继续走onTouchEvent(event) 。这个大家可以对照前面的内容去理解。
那么下面就看看onTouchEvent(event)是怎么执行的吧！
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">onTouchEvent</span>(MotionEvent <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>) { final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getX(); final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getY(); final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> viewFlags = mViewFlags; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((viewFlags & ENABLED_MASK) == DISABLED) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getAction() == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) { setPressed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// A disabled view that is clickable still consumes the touch</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// events, it just doesn't respond to them.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> (((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mTouchDelegate != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mTouchDelegate.onTouchEvent(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (((viewFlags & CLICKABLE) == CLICKABLE || (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getAction()) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> MotionEvent.ACTION_UP: boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((mPrivateFlags & PFLAG_PRESSED) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> || prepressed) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// take focus if we don't have it already and we should in</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// touch mode.</span> boolean focusTaken = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (isFocusable() && isFocusableInTouchMode() && !isFocused()) { focusTaken = requestFocus(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (prepressed) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// The button is being released before we actually</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// showed it as pressed. Make it show the pressed</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// state now (before scheduling the click) to ensure</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// the user sees it.</span> setPressed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>, x, y); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!mHasPerformedLongPress) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// This is a tap, so remove the longpress check</span> removeLongPressCallback(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Only perform take click actions if we were in the pressed state</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!focusTaken) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Use a Runnable and post this rather than calling</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// performClick directly. This lets other visual state</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// of the view update before click actions start.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mPerformClick == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mPerformClick = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> PerformClick(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!post(mPerformClick)) { performClick(); } } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mUnsetPressedState == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mUnsetPressedState = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> UnsetPressedState(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (prepressed) { postDelayed(mUnsetPressedState, ViewConfiguration.getPressedStateDuration()); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!post(mUnsetPressedState)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// If the post failed, unpress right now</span> mUnsetPressedState.run(); } removeTapCallback(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> MotionEvent.ACTION_DOWN: mHasPerformedLongPress = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (performButtonActionOnTouchDown(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>)) {//重点部分下面会解释 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Walk up the hierarchy to determine if we're inside a scrolling container.</span> boolean isInScrollingContainer = isInScrollingContainer(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// For views inside a scrolling container, delay the pressed feedback for</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// a short period in case this is a scroll.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (isInScrollingContainer) { mPrivateFlags |= PFLAG_PREPRESSED; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mPendingCheckForTap == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mPendingCheckForTap = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> CheckForTap(); } mPendingCheckForTap.x = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getX(); mPendingCheckForTap.y = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getY(); postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout()); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Not inside a scrolling container, so show the feedback right away</span> setPressed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>, x, y); checkForLongClick(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> MotionEvent.ACTION_CANCEL: setPressed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); removeTapCallback(); removeLongPressCallback(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> MotionEvent.ACTION_MOVE: drawableHotspotChanged(x, y); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Be lenient about moving outside of buttons</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!pointInView(x, y, mTouchSlop)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Outside button</span> removeTapCallback(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((mPrivateFlags & PFLAG_PRESSED) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Remove any future long press/tap checks</span> removeLongPressCallback(); setPressed(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>); } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li><li style="box-sizing: border-box; padding: 0px 5px;">87</li><li style="box-sizing: border-box; padding: 0px 5px;">88</li><li style="box-sizing: border-box; padding: 0px 5px;">89</li><li style="box-sizing: border-box; padding: 0px 5px;">90</li><li style="box-sizing: border-box; padding: 0px 5px;">91</li><li style="box-sizing: border-box; padding: 0px 5px;">92</li><li style="box-sizing: border-box; padding: 0px 5px;">93</li><li style="box-sizing: border-box; padding: 0px 5px;">94</li><li style="box-sizing: border-box; padding: 0px 5px;">95</li><li style="box-sizing: border-box; padding: 0px 5px;">96</li><li style="box-sizing: border-box; padding: 0px 5px;">97</li><li style="box-sizing: border-box; padding: 0px 5px;">98</li><li style="box-sizing: border-box; padding: 0px 5px;">99</li><li style="box-sizing: border-box; padding: 0px 5px;">100</li><li style="box-sizing: border-box; padding: 0px 5px;">101</li><li style="box-sizing: border-box; padding: 0px 5px;">102</li><li style="box-sizing: border-box; padding: 0px 5px;">103</li><li style="box-sizing: border-box; padding: 0px 5px;">104</li><li style="box-sizing: border-box; padding: 0px 5px;">105</li><li style="box-sizing: border-box; padding: 0px 5px;">106</li><li style="box-sizing: border-box; padding: 0px 5px;">107</li><li style="box-sizing: border-box; padding: 0px 5px;">108</li><li style="box-sizing: border-box; padding: 0px 5px;">109</li><li style="box-sizing: border-box; padding: 0px 5px;">110</li><li style="box-sizing: border-box; padding: 0px 5px;">111</li><li style="box-sizing: border-box; padding: 0px 5px;">112</li><li style="box-sizing: border-box; padding: 0px 5px;">113</li><li style="box-sizing: border-box; padding: 0px 5px;">114</li><li style="box-sizing: border-box; padding: 0px 5px;">115</li><li style="box-sizing: border-box; padding: 0px 5px;">116</li><li style="box-sizing: border-box; padding: 0px 5px;">117</li><li style="box-sizing: border-box; padding: 0px 5px;">118</li><li style="box-sizing: border-box; padding: 0px 5px;">119</li><li style="box-sizing: border-box; padding: 0px 5px;">120</li><li style="box-sizing: border-box; padding: 0px 5px;">121</li><li style="box-sizing: border-box; padding: 0px 5px;">122</li><li style="box-sizing: border-box; padding: 0px 5px;">123</li><li style="box-sizing: border-box; padding: 0px 5px;">124</li><li style="box-sizing: border-box; padding: 0px 5px;">125</li><li style="box-sizing: border-box; padding: 0px 5px;">126</li><li style="box-sizing: border-box; padding: 0px 5px;">127</li><li style="box-sizing: border-box; padding: 0px 5px;">128</li><li style="box-sizing: border-box; padding: 0px 5px;">129</li><li style="box-sizing: border-box; padding: 0px 5px;">130</li><li style="box-sizing: border-box; padding: 0px 5px;">131</li></ul>代码比较长，我们就从重点看吧，Android的控件默认都是enable的,所以第一个if跳过,直接看第三个if,控件是否可点击(或者是是否有长按事件)进入switch中。
而事件通常重要的有如下三种它也是switch中的主要内容：
MotionEvent.ACTION_DOWN 按下View，是所有事件的开始
MotionEvent.ACTION_MOVE 滑动事件
MotionEvent.ACTION_UP 与down对应，表示抬起
ACTION_DOWN，首先判断当前点击down事件的操作，如果点击到menu时，显示菜单，返回true，程序直接跳出。如果程序执行完Down返回false的话后面的Move.Up就不会执行 。
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> boolean <span class="hljs-title" style="box-sizing: border-box;">performButtonActionOnTouchDown</span>(MotionEvent <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getButtonState() & MotionEvent.BUTTON_SECONDARY) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (showContextMenu(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getX(), <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getY(), <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">event</span>.getMetaState())) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li></li></ul>ACTION_UP，按不按的那一堆直接跳过，直接看核心代码 performClick()。
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">performClick</span>() { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> result; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ListenerInfo li = mListenerInfo; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (li != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && li.mOnClickListener != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { playSoundEffect(SoundEffectConstants.CLICK); li.mOnClickListener.onClick(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>); result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { result = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; } sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> result; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>这里看到了熟悉的代码onClick()，只要li和li.mOnClickListener不为空，onClick()就会被执行，上面说过li不会为空，li.mOnClickListener赋值如下:
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setOnClickListener</span>(OnClickListener l) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!isClickable()) { setClickable(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>); } getListenerInfo().mOnClickListener = l; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li></li></ul>只要注册了点击事件li.mOnClickListener也不会为空，所以只要你注册点击事件onClick()就会被执行，当然前提是执行Up事件哦! 给大家一张图并且咱们也稍微总结一下吧！
在这里稍微总结一下咯，当控件被点击时，首先会触发dispatchTouchEvent(MotionEvent ev)事件，例如这里的button看它的源码它没有这个方法，那么看它的父类textview也没有，最后我们在view中找到了，那么就从view开始分发这个点击事件，如果返回为true那么事件就被消费啦（这里也就是说执行了onTouchEvent(MotionEvent ev)方法，并且它返回了true），button就无法再去消费这个事件，反之继续向下分发，分发到button执行onTouchEvent(MotionEvent ev)这个方法如果返回true那么事件就被消费啦，如果返回为false就未被消费，紧接着就会返回到它的上一层view去执行onTouchEvent(MotionEvent ev)这个方法，如果都返回为false，那么这个点击事件就消失了。
viewgroup的事件分发机制源码
先来看viewgroup的dispatchTouchEvent(event)
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">dispatchTouchEvent</span>(MotionEvent ev) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mInputEventConsistencyVerifier != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mInputEventConsistencyVerifier.onTouchEvent(ev, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> handled = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (onFilterTouchEventForSecurity(ev)) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> action = ev.getAction(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> actionMasked = action & MotionEvent.ACTION_MASK; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Handle an initial down.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (actionMasked == MotionEvent.ACTION_DOWN) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Throw away all previous state when starting a new touch gesture.</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// The framework may have dropped the up or cancel event for the previous gesture</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// due to an app switch, ANR, or some other state change.</span> cancelAndClearTouchTargets(ev); resetTouchState(); } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Check for interception.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> intercepted; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (actionMasked == MotionEvent.ACTION_DOWN || mFirstTouchTarget != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!disallowIntercept) { intercepted = onInterceptTouchEvent(ev); ev.setAction(action); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// restore action in case it was changed</span> } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { intercepted = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// There are no touch targets and this action is not an initial down</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// so this view group continues to intercept touches.</span> intercepted = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Check for cancelation.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> canceled = resetCancelNextUpFlag(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>) || actionMasked == MotionEvent.ACTION_CANCEL; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Update list of touch targets for pointer down, if needed.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; TouchTarget newTouchTarget = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> alreadyDispatchedToNewTouchTarget = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!canceled && !intercepted) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (actionMasked == MotionEvent.ACTION_DOWN || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN) || actionMasked == MotionEvent.ACTION_HOVER_MOVE) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> actionIndex = ev.getActionIndex(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// always 0 for down</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> idBitsToAssign = split ? <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> << ev.getPointerId(actionIndex) : TouchTarget.ALL_POINTER_IDS; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Clean up earlier touch targets for this pointer id in case they</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// have become out of sync.</span> removePointersFromTouchTargets(idBitsToAssign); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> childrenCount = mChildrenCount; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (newTouchTarget == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && childrenCount != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x = ev.getX(actionIndex); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y = ev.getY(actionIndex); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Find a child that can receive the event.</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Scan children from front to back.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ArrayList<View> preorderedList = buildOrderedChildList(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> customOrder = preorderedList == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && isChildrenDrawingOrderEnabled(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> View[] children = mChildren; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = childrenCount - <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>; i >= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i--) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> childIndex = customOrder ? getChildDrawingOrder(childrenCount, i) : i; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> View child = (preorderedList == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) ? children[childIndex] : preorderedList.get(childIndex); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!canViewReceivePointerEvents(child) || !isTransformedTouchPointInView(x, y, child, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>; } newTouchTarget = getTouchTarget(child); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (newTouchTarget != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Child is already receiving touch within its bounds.</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Give it the new pointer in addition to the ones it is handling.</span> newTouchTarget.pointerIdBits |= idBitsToAssign; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } resetCancelNextUpFlag(child); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (dispatchTransformedTouchEvent(ev, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>, child, idBitsToAssign)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Child wants to receive touch within its bounds.</span> mLastTouchDownTime = ev.getDownTime(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (preorderedList != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// childIndex points into presorted list, find original index</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> j = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; j < childrenCount; j++) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (children[childIndex] == mChildren[j]) { mLastTouchDownIndex = j; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { mLastTouchDownIndex = childIndex; } mLastTouchDownX = ev.getX(); mLastTouchDownY = ev.getY(); newTouchTarget = addTouchTarget(child, idBitsToAssign); alreadyDispatchedToNewTouchTarget = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (preorderedList != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) preorderedList.clear(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (newTouchTarget == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> && mFirstTouchTarget != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Did not find a child to receive the event.</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Assign the pointer to the least recently added target.</span> newTouchTarget = mFirstTouchTarget; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (newTouchTarget.next != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { newTouchTarget = newTouchTarget.next; } newTouchTarget.pointerIdBits |= idBitsToAssign; } } } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Dispatch to touch targets.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mFirstTouchTarget == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// No touch targets so treat this as an ordinary view.</span> handled = dispatchTransformedTouchEvent(ev, canceled, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>, TouchTarget.ALL_POINTER_IDS); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Dispatch to touch targets, excluding the new touch target if we already</span> <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// dispatched to it. Cancel touch targets if necessary.</span> TouchTarget predecessor = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>; TouchTarget target = mFirstTouchTarget; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (target != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> TouchTarget next = target.next; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) { handled = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> cancelChild = resetCancelNextUpFlag(target.child) || intercepted; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (dispatchTransformedTouchEvent(ev, cancelChild, target.child, target.pointerIdBits)) { handled = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (cancelChild) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (predecessor == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mFirstTouchTarget = next; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { predecessor.next = next; } target.recycle(); target = next; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>; } } predecessor = target; target = next; } } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Update list of touch targets for pointer up or cancel, if needed.</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (canceled || actionMasked == MotionEvent.ACTION_UP || actionMasked == MotionEvent.ACTION_HOVER_MOVE) { resetTouchState(); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (split && actionMasked == MotionEvent.ACTION_POINTER_UP) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> actionIndex = ev.getActionIndex(); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> idBitsToRemove = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> << ev.getPointerId(actionIndex); removePointersFromTouchTargets(idBitsToRemove); } } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!handled && mInputEventConsistencyVerifier != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mInputEventConsistencyVerifier.onUnhandledEvent(ev, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>); } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> handled; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li><li style="box-sizing: border-box; padding: 0px 5px;">87</li><li style="box-sizing: border-box; padding: 0px 5px;">88</li><li style="box-sizing: border-box; padding: 0px 5px;">89</li><li style="box-sizing: border-box; padding: 0px 5px;">90</li><li style="box-sizing: border-box; padding: 0px 5px;">91</li><li style="box-sizing: border-box; padding: 0px 5px;">92</li><li style="box-sizing: border-box; padding: 0px 5px;">93</li><li style="box-sizing: border-box; padding: 0px 5px;">94</li><li style="box-sizing: border-box; padding: 0px 5px;">95</li><li style="box-sizing: border-box; padding: 0px 5px;">96</li><li style="box-sizing: border-box; padding: 0px 5px;">97</li><li style="box-sizing: border-box; padding: 0px 5px;">98</li><li style="box-sizing: border-box; padding: 0px 5px;">99</li><li style="box-sizing: border-box; padding: 0px 5px;">100</li><li style="box-sizing: border-box; padding: 0px 5px;">101</li><li style="box-sizing: border-box; padding: 0px 5px;">102</li><li style="box-sizing: border-box; padding: 0px 5px;">103</li><li style="box-sizing: border-box; padding: 0px 5px;">104</li><li style="box-sizing: border-box; padding: 0px 5px;">105</li><li style="box-sizing: border-box; padding: 0px 5px;">106</li><li style="box-sizing: border-box; padding: 0px 5px;">107</li><li style="box-sizing: border-box; padding: 0px 5px;">108</li><li style="box-sizing: border-box; padding: 0px 5px;">109</li><li style="box-sizing: border-box; padding: 0px 5px;">110</li><li style="box-sizing: border-box; padding: 0px 5px;">111</li><li style="box-sizing: border-box; padding: 0px 5px;">112</li><li style="box-sizing: border-box; padding: 0px 5px;">113</li><li style="box-sizing: border-box; padding: 0px 5px;">114</li><li style="box-sizing: border-box; padding: 0px 5px;">115</li><li style="box-sizing: border-box; padding: 0px 5px;">116</li><li style="box-sizing: border-box; padding: 0px 5px;">117</li><li style="box-sizing: border-box; padding: 0px 5px;">118</li><li style="box-sizing: border-box; padding: 0px 5px;">119</li><li style="box-sizing: border-box; padding: 0px 5px;">120</li><li style="box-sizing: border-box; padding: 0px 5px;">121</li><li style="box-sizing: border-box; padding: 0px 5px;">122</li><li style="box-sizing: border-box; padding: 0px 5px;">123</li><li style="box-sizing: border-box; padding: 0px 5px;">124</li><li style="box-sizing: border-box; padding: 0px 5px;">125</li><li style="box-sizing: border-box; padding: 0px 5px;">126</li><li style="box-sizing: border-box; padding: 0px 5px;">127</li><li style="box-sizing: border-box; padding: 0px 5px;">128</li><li style="box-sizing: border-box; padding: 0px 5px;">129</li><li style="box-sizing: border-box; padding: 0px 5px;">130</li><li style="box-sizing: border-box; padding: 0px 5px;">131</li><li style="box-sizing: border-box; padding: 0px 5px;">132</li><li style="box-sizing: border-box; padding: 0px 5px;">133</li><li style="box-sizing: border-box; padding: 0px 5px;">134</li><li style="box-sizing: border-box; padding: 0px 5px;">135</li><li style="box-sizing: border-box; padding: 0px 5px;">136</li><li style="box-sizing: border-box; padding: 0px 5px;">137</li><li style="box-sizing: border-box; padding: 0px 5px;">138</li><li style="box-sizing: border-box; padding: 0px 5px;">139</li><li style="box-sizing: border-box; padding: 0px 5px;">140</li><li style="box-sizing: border-box; padding: 0px 5px;">141</li><li style="box-sizing: border-box; padding: 0px 5px;">142</li><li style="box-sizing: border-box; padding: 0px 5px;">143</li><li style="box-sizing: border-box; padding: 0px 5px;">144</li><li style="box-sizing: border-box; padding: 0px 5px;">145</li><li style="box-sizing: border-box; padding: 0px 5px;">146</li><li style="box-sizing: border-box; padding: 0px 5px;">147</li><li style="box-sizing: border-box; padding: 0px 5px;">148</li><li style="box-sizing: border-box; padding: 0px 5px;">149</li><li style="box-sizing: border-box; padding: 0px 5px;">150</li><li style="box-sizing: border-box; padding: 0px 5px;">151</li><li style="box-sizing: border-box; padding: 0px 5px;">152</li><li style="box-sizing: border-box; padding: 0px 5px;">153</li><li style="box-sizing: border-box; padding: 0px 5px;">154</li><li style="box-sizing: border-box; padding: 0px 5px;">155</li><li style="box-sizing: border-box; padding: 0px 5px;">156</li><li style="box-sizing: border-box; padding: 0px 5px;">157</li><li style="box-sizing: border-box; padding: 0px 5px;">158</li><li style="box-sizing: border-box; padding: 0px 5px;">159</li><li style="box-sizing: border-box; padding: 0px 5px;">160</li><li style="box-sizing: border-box; padding: 0px 5px;">161</li><li style="box-sizing: border-box; padding: 0px 5px;">162</li><li style="box-sizing: border-box; padding: 0px 5px;">163</li><li style="box-sizing: border-box; padding: 0px 5px;">164</li><li style="box-sizing: border-box; padding: 0px 5px;">165</li><li style="box-sizing: border-box; padding: 0px 5px;">166</li><li style="box-sizing: border-box; padding: 0px 5px;">167</li><li style="box-sizing: border-box; padding: 0px 5px;">168</li><li style="box-sizing: border-box; padding: 0px 5px;">169</li><li style="box-sizing: border-box; padding: 0px 5px;">170</li><li style="box-sizing: border-box; padding: 0px 5px;">171</li><li style="box-sizing: border-box; padding: 0px 5px;">172</li><li style="box-sizing: border-box; padding: 0px 5px;">173</li><li style="box-sizing: border-box; padding: 0px 5px;">174</li><li style="box-sizing: border-box; padding: 0px 5px;">175</li><li style="box-sizing: border-box; padding: 0px 5px;">176</li><li></li></ul>首先判断当前是不是down状态或者是首次touch,然后判断disallowIntercept的值,默认情况下为false,你也可以通过调用下面这个方法改变它的值
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">requestDisallowInterceptTouchEvent</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> disallowIntercept) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// We're already in this state, assume our ancestors are too</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (disallowIntercept) { mGroupFlags |= FLAG_DISALLOW_INTERCEPT; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> { mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT; } <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Pass it up to our parent</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mParent != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) { mParent.requestDisallowInterceptTouchEvent(disallowIntercept); } }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li></ul>继续上面说的,怎么突然间出现了onInterceptTouchEvent(),这个方法就是传说中的事件拦截了
<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> <span class="hljs-title" style="box-sizing: border-box;">onInterceptTouchEvent</span>(MotionEvent ev) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>原来这个高大上的拦截事件就两行,直接给你return false,也就说默认情况下是不拦截的,当然There are no touch targets and this action is not an initial down的情况下也是拦截的.如果当前事件被拦截,事件就不再向下分发,如果当前事件没有被拦截并且没有取消，继续走view的事件分发。
总结一下viewgroup的事件分发吧，我的理解呢就是重点方法就是onInterceptTouchEvent()了，不论是ViewGroup还是View，都由它来处理事件的消费和传递。看图理解吧。
举个栗子，看下图：
描述情景L内嵌套R，R内嵌套B，当手指点击按钮B时，事件传递的顺序是从底向上传递的，也就是按照L（LinearLayout）->R（RelativeLayout）->B（Button）的顺序由下往上逐层传递，响应正好相反，是自上而下。
L首先接收到点击事件，L的父类是ViewGroup类，并将事件传递给dispatchTouchEvent方法，dispatchTouchEvent函数中判断该控件L是否重载了onInterceptTouchEvent方法进行事件拦截，onInterceptTouchEvent默认返回false不拦截，那么dispatchTouchEvent方法将事件传递给R去处理（进入第2流程处理），如果返回true表示当前L控件拦截了事件向其它控件的传递，交给它自己父类View的dispatchTouchEvent去处理，在父方法的dispatchTouchEvent中，将会按照前面讲的View的事件处理机制去判断，比如判断L是否重载了onTouch方法，是否可点击，是否做了监听等事件。
R也是ViewGroup的子类，因此与第1流程基本相似，如果onInterceptTouchEvent返回了false，表示事件将不拦截继续传递给B。
B是View的子类，它没有onInterceptTouchEvent方法，直接交给自己父类View的dispatchTouchEvent去处理，流程同不再敷述。
onInterceptTouchEvent只有ViewGroup才有，当一个控件是继承自ViewGroup而来的，那么它就可能会有子控件，因此，才有可能传递给子控件，而继承自View的控件，不会有子控件，也就没有onInterceptTouchEvent函数了。通过dispatchTouchEvent分发的控件返回值True和false，表示当前控件是否消费了传递过来的事件，如果消费了，返回True，反之false。消费了，就不再继续传递了，没有消费，如果有子控件将继续传递。onInterceptTouchEvent主要来决定当前控件是否需要拦截传递给子控件，如果返回True表示该控件拦截，并交由自己父类的dispatchTouchEvent处理消费，如果返回false表示不拦截，允许传递给子控件处理。
说了这么多自己算是理解的差不多了，大家理解了吗？如果没理解也没事，多看几遍总有一天会理解的。本来要来几个实际应用的例子，感觉太长了，后面再写咯！大家早上好啊！拜拜。
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