文章大纲

• 引言
• 一、Android 事件分发概述
• 二、Touch事件分发的对象MotionEvent
• 三、分发事件的核心对象及方法
• • 1、分发事件的核心对象
  • 2、事件分发的核心方法
• 四、Touch事件分发的流程
• • 1、Activity的事件处理流程
  • 2、ViewGroup&View的事件分发流程
• 五、事件分发的应用
• • 1、事件拦截
  • 2、响应点击事件

引言

Android 事件详细总结。

该文章基于android-28，仅分析Framework java层代码逻辑，仅供参考，不敢保证百分百正确无误。

一、Android 事件分发概述

一般说来当用户触摸屏幕或者按键操作，首次触发的是底层硬件驱动，驱动收到事件后并将该相应事件写入到输入设备节点， 便产生最原生态的内核事件。接着，输入（Input）系统取出原生态的事件再经过层层封装后成为KeyEvent或者MotionEvent ，最后交付给相应的目标窗口(Window)来消费该输入事件。其中Input模块的主要组成有：

• Native层的InputReader负责从EventHub取出事件并处理，再交给InputDispatcher；
• Native层的InputDispatcher接收来自InputReader的输入事件，并记录WMS（WindowManagerService）的窗口信息，用于派发事件到合适的窗口；
• Java层的InputManagerService跟WMS交互，WMS记录所有窗口信息，并同步更新到IMS，为InputDispatcher正确派发事件到ViewRootImpl提供保障。

简而言之，Android 中事件传递按照从上到下进行层级传递，事件处理从 Activity 开始到 ViewGroup 再到 View。事件传递方法包括dispatchTouchEvent、onTouchEvent、onInterceptTouchEvent，其中前两个是 View 和 ViewGroup 都有的，最后一个是只有 ViewGroup 才有的方法。其中onTouch 方法要先于 onClick 触发执行，onTouch 在 dispatchTouchEvent 中被调用，而 onClick 在 onTouchEvent 方法中被调用，因此onTouchEvent 要后于 dispatchTouchEvent 方法的调用。

二、Touch事件分发的对象MotionEvent

MotionEvent 继承自InputEvent并实现Parcelable接口，作为事件分发机制的核心对象，在Android中当用户触摸屏幕上的View 或 ViewGroup（及其子View），将产生点击事件（Touch事件）并根据Touch事件的发生时触摸的位置、时间、类型等相关细节封装不同类型的MotionEvent对象进行传递，该对象用于记录所有与移动相关的事件信息（事件分发和处理由Activity去调用native层完成），比较典型的有以上四种：

事件ACTION触发场景单次事件流中触发的次数

MotionEvent.ACTION_DOWN	在屏幕被按下时（所有事件的源头）	1次
MotionEvent.ACTION_MOVE	在屏幕上进行滑动时	0次或者多次
MotionEvent.ACTION_UP	从屏幕上抬起时	0次或者1次
MotionEvent.ACTION_CANCEL	结束事件（非人为原因）	0或者1次

所以一次完整的MotionEvent事件，是从用户触摸屏幕到离开屏幕。整个过程的动作序列：ACTION_DOWN(1次) —> ACTION_MOVE(N次) -> ACTION_UP(1次)。

而对于多点触摸，每一个触摸点Pointer会有一个id和index。对于多指操作，通过pointerindex来获取指定Pointer的触屏位置。比如单点操作时通过getX()获取x坐标，而多点操作时通过getX(pointerindex)获取x坐标。

MotionEvent 还有很多的ACTION类型，MotionEvent需要继承native 层InputEvent（其实是内核层的Input机制），因为Android Framework 通过JNI 进行处理，同时需要跨进程因而MotionEvent实现了Parcelable序列化接口。

三、分发事件的核心对象及方法

1、分发事件的核心对象

• Activity——作为Android四大基本组件之一，当手指触摸到屏幕时，屏幕硬件逐行不断地扫描每个像素点，获取到触摸事件后，从底层产生中断上报。再通过native层调用Java层InputEventReceiver中的dispatchInputEvent方法。最后经过层层调用交由Activity的dispatchTouchEvent方法来处理。

• View——作为所有视图对象的父类，实现了Drawable.Callback（动画相关的接口）、KeyEvent.Callback（按键相关的接口）和AccessibilityEventSource（交互相关的接口）。

• ViewGroup——ViewGroup是一个继承了View并实现了ViewParent（用于与父视图交互的接口）， ViewManager（用于添加、删除、更新子视图到Activity的接口）的抽象类，作为盛放其他View的容器，可以包含View和ViewGroup，是所有布局的父类或间接父类。

2、事件分发的核心方法

Touch事件都源自按下屏幕里Activity中的View或者ViewGroup（及其子View），所以事件的处理都是由Activity、View或ViewGroup对象完成的，换言之，只在Activity、View或ViewGroup里拥有处理事件系列方法如下表所示：

从源码中可以得知在Activity、 ViewGroup 和View中都存在 dispatchTouchEvent 和 onTouchEvent 方法（但是在 ViewGroup 中还有一个 onInterceptTouchEvent 方法），他们都接受了一个MotionEvent类型的参数用于标记各种动作事件且返回值都是boolean型，true则代表不往下传递，false则表示继续往下传递，那么这些方法有何功能的呢？

• boolean dispatchTouchEvent(MotionEvent event)——负责Touch事件的分发，Android 中所有的事件都必须经过此方法的分发，然后决定是自身消费当前事件还是继续往下分发给子View返回 true 则表示不继续分发，反之返回 false 则继续往下分发；而如果ViewGroup 则是先分发给 onInterceptTouchEvent 进行判断是否拦截该事件。

• boolean onTouchEvent(MotionEvent event)—— 负责Touch事件的处理，返回 true 则表示消费当前事件，反之返回 false 则不处理交给子View继续进行分发。

• boolean onInterceptTouchEvent(MotionEvent event)—— 负责Touch事件的拦截 返回 true 则表示拦截当前事件就不继续往下分发，交给自身的 onTouchEvent 进行处理；而返回 false 则不拦截，继续往下传。这是 ViewGroup 特有的方法，因为 ViewGroup 作为容器可以存放其他子 View，而View 则不能，换言之，只有 ViewGroup才有拦截事件的能力。

事件分发的核心流程都是围绕这些方法进行的，由不同的对象直接或者间接调用进行处理。

四、Touch事件分发的流程

事件分发有多种类型, 以下是Touch相关的事件分发大致流程：
Activity——>Window（PhoneWindow）——>DecorView——>ViewGroup——>View。

1、Activity的事件处理流程

事件的分发是由Activity开始的，当用户点击屏幕的时候首先接触到的就是Activity，从而触发Activity#dispatchTouchEvent方法，

/*** android.app.Activity#dispatchTouchEvent* 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) {//如果是DOWN类型则说明是一个全新的事件if (ev.getAction() == MotionEvent.ACTION_DOWN) {//默认为空实现，可以被重写，如果你想要知道用户已经与Activity进行交互onUserInteraction();}//调用Window的dispatchTouchEvent方法,并把事件分发至PhoneWindow（获取当前Activity的顶层窗口是PhoneWindow），返回false表示当前事件没有被消费。if (getWindow().superDispatchTouchEvent(ev)) {return true;}//如果PhoneWindow消费了事件则把事件分发至Activity的onTouchEventreturn onTouchEvent(ev);}

Activity#dispatchTouchEvent返回结果之前，会先分发到ViewGroup&View，而最终的执行分为两个分支（抛开中间细节）：

• getWindow().superDispatchTouchEvent(ev)返回flase时，代表当前事件没有被Activity中的任何View或者ViewGroup处理（即DecorView #dispatchTouchEvent方法返回false），则此次事件最终是由Activity#onTouchEvent 去处理的。

/***android.app.Activity#onTouchEvent* 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) {//判断是否屏幕出界，比如说点击到屏幕的非有效区域时，当窗口需要关闭时，消费掉当前eventif (mWindow.shouldCloseOnTouch(this, event)) {finish();return true;}return false;}

• getWindow().superDispatchTouchEvent(ev)返回true时，代表事件已被Activity中的View或者ViewGroup消费了。

再回到分发流程，Activity#dispatchTouchEvent执行后，接着会通过getWindow()方法得到当前Activity的顶层窗口（即PhoneWindow）并调用它的superDispatchTouchEvent方法把事件分发到PhoneWindow，执行PhoneWindow#superDispatchTouchEvent方法传入到DecorView（根ViewGroup）…

DecorView继承自 FrameLayout 并实现了RootViewSurfaceTaker和WindowCallbacks接口，是当前界面的最外（顶）层容器，即setContentView方法所设置的View的父容器根ViewGroup。

//com.android.internal.policy.PhoneWindow#superDispatchTouchEvent@Overridepublic boolean superDispatchTouchEvent(MotionEvent event) {//分发至DecorViewreturn mDecor.superDispatchTouchEvent(event);}

分发到DecorView，再通过DecorView#superDispatchTouchEvent方法

//com.android.internal.policy.DecorView#superDispatchTouchEventpublic boolean superDispatchTouchEvent(MotionEvent event) {return super.dispatchTouchEvent(event);//实际上调用的是ViewGroup#dispatchTouchEvent}

接下来分发到了ViewGroup中，ViewGroup的分发流程比较复杂，篇幅有限会省略部分逻辑。

2、ViewGroup&View的事件分发流程

ViewGroup&View的事件分发流程的起点是从PhoneWindow#superDispatchTouchEvent开始的，首先分发至根ViewGroup（DecorView）并执行ViewGroup#dispatchTouchEvent方法。

//android.view.ViewGroup#dispatchTouchEventpublic boolean dispatchTouchEvent(MotionEvent ev) {//辅助功能跨进程调用，是当前应用与系统层进行交互的，模拟的点击事件if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onTouchEvent(ev, 1);}...//是否消费了当前事件的标识，最终的返回值boolean handled = false;//根据隐私策略而来决定是否过滤本次触摸事件,相当于是检测当前事件，功能类似检测操作UI时是否在主线程中if (onFilterTouchEventForSecurity(ev)) {final int action = ev.getAction();final int actionMasked = action & MotionEvent.ACTION_MASK;if (actionMasked == MotionEvent.ACTION_DOWN) {// 发生ACTION_DOWN事件, 则取消并清除之前所有的触摸targets，可能是由于App切换、ANR或者其他原因抛弃了上一次的UP或者CANCEL，需要取消并移除所有目标cancelAndClearTouchTargets(ev);resetTouchState(); // 重置触摸状态为下一次循环做准备}// 发生ACTION_DOWN事件或者已经发生过ACTION_DOWN;才进入此区域，主要功能是拦截器//第一次触摸屏幕时是DOWN，只有发生过ACTION_DOWN事件，则mFirstTouchTarget != null;final boolean intercepted;if (actionMasked == MotionEvent.ACTION_DOWN|| mFirstTouchTarget != null) {//可以通过在其子View中去调用父ViewGroup的requestDisallowInterceptTouchEvent方法设置是否允许拦截，让父View是否拦截事件final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;//判断是否允许调用拦截器if (!disallowIntercept) {//！！调用拦截逻辑的方法！！intercepted = onInterceptTouchEvent(ev);ev.setAction(action);} else {intercepted = false;}} else {// 当没有触摸targets，且不是down事件时，开始持续拦截触摸。intercepted = true;}...//不取消事件，同时不拦截事件, 并且是Down事件时if (!canceled && !intercepted) {//把事件分发给所有的子视图，寻找可以获取焦点的视图。View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()? findChildWithAccessibilityFocus() : null;if (actionMasked == MotionEvent.ACTION_DOWN|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {final int actionIndex = ev.getActionIndex(); // down事件等于0final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex): TouchTarget.ALL_POINTER_IDS;removePointersFromTouchTargets(idBitsToAssign); //清空早先的触摸对象final int childrenCount = mChildrenCount;//第一次down事件，同时子视图不会空时if (newTouchTarget == null && childrenCount != 0) {final float x = ev.getX(actionIndex);final float y = ev.getY(actionIndex);// Find a child that can receive the event. Scan children from front to back.//创建可以接收事件的子View，并按照z轴值对子View进行排序，因为子View可能存在相互重叠的部分，从顶层到底层排序final ArrayList<View> preorderedList = buildTouchDispatchChildList();final boolean customOrder = preorderedList == null&& isChildrenDrawingOrderEnabled();//当前ViewGroup 中所有的子View数组final View[] children = mChildren;/* 倒序遍历，从底层到顶层，从最底层的父视图开始遍历， ** 找寻newTouchTarget，并赋予view与 pointerIdBits； ** 如果已经存在找寻newTouchTarget，说明正在接收触摸事件，则跳出循环。 */for (int i = childrenCount - 1; i >= 0; i--) {final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);//获取当前ViewGroup中的子Viewfinal View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);// 如果当前视图无法获取用户焦点，则跳过本次循环if (childWithAccessibilityFocus != null) {if (childWithAccessibilityFocus != child) {continue;}childWithAccessibilityFocus = null;i = childrenCount - 1;}//如果view不可见或正在执行动画，或者触摸的坐标点不在view的范围内，则跳过本次循环if (!canViewReceivePointerEvents(child)|| !isTransformedTouchPointInView(x, y, child, null)) {ev.setTargetAccessibilityFocus(false);continue;}//获取当前的View的包装对象newTouchTarget = getTouchTarget(child);// 已经开始接收触摸事件,并退出整个循环。if (newTouchTarget != null) {newTouchTarget.pointerIdBits |= idBitsToAssign;break;}//重置取消或抬起标志位resetCancelNextUpFlag(child);//如果触摸位置在child的区域内，则把事件分发给子View或ViewGroup，开始事件分发，child为null时传递到View#dispatchTouchEvent,而child不为null时则调用child自身的dispatchTouchEventif (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) { // [见小节2.4.4]// 获取TouchDown的时间点mLastTouchDownTime = ev.getDownTime();// 获取TouchDown的Indexif (preorderedList != null) {for (int j = 0; j < childrenCount; j++) {if (children[childIndex] == mChildren[j]) {mLastTouchDownIndex = j;break;}}} else {mLastTouchDownIndex = childIndex;}//获取TouchDown的x,y坐标mLastTouchDownX = ev.getX();mLastTouchDownY = ev.getY();//添加TouchTarget,则mFirstTouchTarget != null，给mFirstTouchTarget赋值newTouchTarget = addTouchTarget(child, idBitsToAssign);//表示以及分发给NewTouchTargetalreadyDispatchedToNewTouchTarget = true;break;}ev.setTargetAccessibilityFocus(false);}// 清除视图列表if (preorderedList != null) preorderedList.clear();}if (newTouchTarget == null && mFirstTouchTarget != null) {//将mFirstTouchTarget的链表最后的touchTarget赋给newTouchTargetnewTouchTarget = mFirstTouchTarget;while (newTouchTarget.next != null) {newTouchTarget = newTouchTarget.next;}newTouchTarget.pointerIdBits |= idBitsToAssign;}}}///#endif if (!canceled && !intercepted)//ViewGroup进行事件拦截之后直接越过前面的逻辑，执行到这里，mFirstTouchTarget赋值是在通过addTouchTarget方法获取的；// 只有处理ACTION_DOWN事件，才会进入addTouchTarget方法。这也正是当View没有消费ACTION_DOWN事件，则不会接收其他MOVE,UP等事件的原if (mFirstTouchTarget == null) {//没有触摸target,则由当前ViewGroup来处理handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);} else {//如果View消费ACTION_DOWN事件，那么MOVE,UP等事件相继开始执行TouchTarget predecessor = null;TouchTarget target = mFirstTouchTarget;while (target != null) {final TouchTarget next = target.next;if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {handled = true;} else {final boolean cancelChild = resetCancelNextUpFlag(target.child)|| intercepted;if (dispatchTransformedTouchEvent(ev, cancelChild,target.child, target.pointerIdBits)) {handled = true;}if (cancelChild) {if (predecessor == null) {mFirstTouchTarget = next;} else {predecessor.next = next;}target.recycle();target = next;continue;}}predecessor = target;target = next;}}//当发生抬起或取消事件，更新触摸targetsif (canceled|| actionMasked == MotionEvent.ACTION_UP|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {resetTouchState();} else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {final int actionIndex = ev.getActionIndex();final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);removePointersFromTouchTargets(idBitsToRemove);}} //此处大括号，是if (onFilterTouchEventForSecurity(ev))的结尾//通知verifier由于当前时间未处理，那么该事件其余的都将被忽略if (!handled && mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);}return handled;}

在ViewGroup每次调用ViewGroup#dispatchTouchEvent方法时，当requestDisallowInterceptTouchEvent方法返回true时则说明允许事件拦截，就会先执行ViewGroup#onInterceptTouchEvent判断是否进行事件拦截，

/*** Implement this method to intercept all touch screen motion events. ** @param ev The motion event being dispatched down the hierarchy.* @return Return true to steal motion events from the children and have* them dispatched to this ViewGroup through onTouchEvent().* The current target will receive an ACTION_CANCEL event, and no further* messages will be delivered here.*/public boolean onInterceptTouchEvent(MotionEvent ev) {if (ev.isFromSource(InputDevice.SOURCE_MOUSE)&& ev.getAction() == MotionEvent.ACTION_DOWN&& ev.isButtonPressed(MotionEvent.BUTTON_PRIMARY)&& isOnScrollbarThumb(ev.getX(), ev.getY())) {return true;}return false;}

返回true则进行拦截，就会越过 if (!canceled && !intercepted)分支，直接执行ViewGroup#dispatchTransformedTouchEvent方法

/*** Transforms a motion event into the coordinate space of a particular child view,* filters out irrelevant pointer ids, and overrides its action if necessary.* If child is null, assumes the MotionEvent will be sent to this ViewGroup instead.* ViewGroup 真正分发事件的逻辑* @param child null则调用View#dispatchTouchEvent;反之则调用child里的dispatchTouchEvent方法*/private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,View child, int desiredPointerIdBits) {final boolean handled;// Canceling motions is a special case. We don't need to perform any transformations// or filtering. The important part is the action, not the contents.final int oldAction = event.getAction();if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {event.setAction(MotionEvent.ACTION_CANCEL);if (child == null) {handled = super.dispatchTouchEvent(event);} else {handled = child.dispatchTouchEvent(event);}event.setAction(oldAction);return handled;}// Calculate the number of pointers to deliver.final int oldPointerIdBits = event.getPointerIdBits();final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;// If for some reason we ended up in an inconsistent state where it looks like we// might produce a motion event with no pointers in it, then drop the event.if (newPointerIdBits == 0) {return false;}// If the number of pointers is the same and we don't need to perform any fancy// irreversible transformations, then we can reuse the motion event for this// dispatch as long as we are careful to revert any changes we make.// Otherwise we need to make a copy.final MotionEvent transformedEvent;if (newPointerIdBits == oldPointerIdBits) {if (child == null || child.hasIdentityMatrix()) {if (child == null) {handled = super.dispatchTouchEvent(event);} else {final float offsetX = mScrollX - child.mLeft;final float offsetY = mScrollY - child.mTop;event.offsetLocation(offsetX, offsetY);handled = child.dispatchTouchEvent(event);event.offsetLocation(-offsetX, -offsetY);}return handled;}transformedEvent = MotionEvent.obtain(event);} else {transformedEvent = event.split(newPointerIdBits);}// Perform any necessary transformations and dispatch.if (child == null) {// 第一次触发Touch事件时执行到这里，去调用父类的dispatchTouchEventhandled = super.dispatchTouchEvent(transformedEvent);} else {final float offsetX = mScrollX - child.mLeft;final float offsetY = mScrollY - child.mTop;transformedEvent.offsetLocation(offsetX, offsetY);if (! child.hasIdentityMatrix()) {transformedEvent.transform(child.getInverseMatrix());}handled = child.dispatchTouchEvent(transformedEvent);}// Done.transformedEvent.recycle();return handled;}

其核心逻辑取决于传入的child，当child =null则调用View#dispatchTouchEvent;反之则调用child自身（有可能是View或ViewGroup）的dispatchTouchEvent方法，假设调用的是View#dispatchTouchEvent方法

/*** Pass the touch screen motion event down to the target view, or this view if it is the target.* @param event The motion event to be dispatched.* @return True if the event was handled by the view, false otherwise.*/public boolean dispatchTouchEvent(MotionEvent event) {// If the event should be handled by accessibility focus first.if (event.isTargetAccessibilityFocus()) {// We don't have focus or no virtual descendant has it, do not handle the event.if (!isAccessibilityFocusedViewOrHost()) {return false;}// We have focus and got the event, then use normal event dispatch.event.setTargetAccessibilityFocus(false);}//是否消费此事件标识，最终的返回值boolean result = false;if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onTouchEvent(event, 0);}final int actionMasked = event.getActionMasked();if (actionMasked == MotionEvent.ACTION_DOWN) {// Defensive cleanup for new gesturestopNestedScroll();}if (onFilterTouchEventForSecurity(event)) {if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {result = true;}//ListenerInfo（可从View#getListenerInfo方法获取）为所有View的事件监听封装类，包含了所有常见事件的监听接口ListenerInfo li = mListenerInfo;//如果外部调用了setOnTouchListener方法时，会先执行OnTouchListener#onTouch，当onTouch返回true时则不会执行View#onTouchEvent方法if (li != null && li.mOnTouchListener != null&& (mViewFlags & ENABLED_MASK) == ENABLED&& li.mOnTouchListener.onTouch(this, event)) {result = true;}if (!result && onTouchEvent(event)) {result = true;}}if (!result && mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);}// Clean up after nested scrolls if this is the end of a gesture; also cancel it if we tried an ACTION_DOWN but we didn't want the rest of the gesture.if (actionMasked == MotionEvent.ACTION_UP ||actionMasked == MotionEvent.ACTION_CANCEL ||(actionMasked == MotionEvent.ACTION_DOWN && !result)) {stopNestedScroll();}return result;}

如果外部调用了setOnTouchListener方法时设置onTouchListener监听时，会先执行View$$OnTouchListener#onTouch，当OnTouchListener#onTouch返回true时则不会执行View#onTouchEvent方法;反之还会去调用View#onTouchEvent方法

/*** Implement this method to handle touch screen motion events.** @param event The motion event.* @return True if the event was handled, false otherwise.*/public boolean onTouchEvent(MotionEvent event) {final float x = event.getX();final float y = event.getY();final int viewFlags = mViewFlags;final int action = event.getAction();// 是否可点击的标志final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;if ((viewFlags & ENABLED_MASK) == DISABLED) {if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {setPressed(false);}mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;// A disabled view that is clickable still consumes the touch// events, it just doesn't respond to them.return clickable;}if (mTouchDelegate != null) {if (mTouchDelegate.onTouchEvent(event)) {return true;}}if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {switch (action) {case MotionEvent.ACTION_UP:mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;if ((viewFlags & TOOLTIP) == TOOLTIP) {handleTooltipUp();}if (!clickable) {removeTapCallback();removeLongPressCallback();mInContextButtonPress = false;mHasPerformedLongPress = false;mIgnoreNextUpEvent = false;break;}boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {// take focus if we don't have it already and we should in// touch mode.boolean focusTaken = false;if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {focusTaken = requestFocus();}if (prepressed) {// The button is being released before we actually// showed it as pressed. Make it show the pressed// state now (before scheduling the click) to ensure// the user sees it.setPressed(true, x, y);}if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {// This is a tap, so remove the longpress checkremoveLongPressCallback();// Only perform take click actions if we were in the pressed stateif (!focusTaken) {// Use a Runnable and post this rather than calling// performClick directly. This lets other visual state// of the view update before click actions start.if (mPerformClick == null) {//PerformClick实现了Runnable接口mPerformClick = new PerformClick();}if (!post(mPerformClick)) {//在该方法内处理Click事件触发OnClickListener.onClick方法performClickInternal();}}}if (mUnsetPressedState == null) {mUnsetPressedState = new UnsetPressedState();}if (prepressed) {postDelayed(mUnsetPressedState,ViewConfiguration.getPressedStateDuration());} else if (!post(mUnsetPressedState)) {// If the post failed, unpress right nowmUnsetPressedState.run();}removeTapCallback();}mIgnoreNextUpEvent = false;break;case MotionEvent.ACTION_DOWN:if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {mPrivateFlags3 |= PFLAG3_FINGER_DOWN;}mHasPerformedLongPress = false;if (!clickable) {checkForLongClick(0, x, y);break;}if (performButtonActionOnTouchDown(event)) {break;}// Walk up the hierarchy to determine if we're inside a scrolling container.boolean isInScrollingContainer = isInScrollingContainer();// For views inside a scrolling container, delay the pressed feedback for// a short period in case this is a scroll.if (isInScrollingContainer) {mPrivateFlags |= PFLAG_PREPRESSED;if (mPendingCheckForTap == null) {mPendingCheckForTap = new CheckForTap();}mPendingCheckForTap.x = event.getX();mPendingCheckForTap.y = event.getY();postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());} else {// Not inside a scrolling container, so show the feedback right awaysetPressed(true, x, y);//处理OnLongClickListener.onLongClick方法checkForLongClick(0, x, y);}break;case MotionEvent.ACTION_CANCEL:if (clickable) {setPressed(false);}removeTapCallback();removeLongPressCallback();mInContextButtonPress = false;mHasPerformedLongPress = false;mIgnoreNextUpEvent = false;mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;break;case MotionEvent.ACTION_MOVE:if (clickable) {drawableHotspotChanged(x, y);}// Be lenient about moving outside of buttonsif (!pointInView(x, y, mTouchSlop)) {// Outside button// Remove any future long press/tap checksremoveTapCallback();removeLongPressCallback();if ((mPrivateFlags & PFLAG_PRESSED) != 0) {setPressed(false);}mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;}break;}return true;}return false;}

所以基本就是在View#onTouchEvent方法的处理onClickListener

private final class PerformClick implements Runnable {@Overridepublic void run() {performClickInternal();}}public boolean performClick() {// We still need to call this method to handle the cases where performClick() was called// externally, instead of through performClickInternal()notifyAutofillManagerOnClick();final boolean result;final ListenerInfo li = mListenerInfo;if (li != null && li.mOnClickListener != null) {playSoundEffect(SoundEffectConstants.CLICK);//处理OnClickListener接口li.mOnClickListener.onClick(this);result = true;} else {result = false;}sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);notifyEnterOrExitForAutoFillIfNeeded(true);return result;}

onLongClickListener等其他监听接口也类似。

五、事件分发的应用

1、事件拦截

拦截事件可以通过两种形式：

• 继承ViewGroup或其子类重写onInterceptTouchEvent方法并返回true。

• 在子View中调用父ViewGroup的requestDisallowInterceptTouchEvent方法并返回true。

2、响应点击事件