Android 事件分发系列文章目录

【Android 事件分发】事件分发源码分析 ( 驱动层通过中断传递事件 | WindowManagerService 向 View 层传递事件 )
【Android 事件分发】事件分发源码分析 ( Activity 中各层级的事件传递 | Activity -＞ PhoneWindow -＞ DecorView -＞ ViewGroup )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制一 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制二 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制三 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制四 | View 事件传递机制 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制五 )
【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制六 )

文章目录

Android 事件分发系列文章目录
一、按下触摸事件记录
二、完整的触摸事件处理机制
三、ViewGroup | dispatchTouchEvent 方法返回
四、ViewGroup 事件分发相关源码
五、View 事件分发相关源码

一、按下触摸事件记录

在上一篇博客【Android 事件分发】事件分发源码分析 ( ViewGroup 事件传递机制五 ) 中 , 着重分析了 ViewGroup 事件分发中 , 触摸事件没有被消费 , 或被父容器拦截的情况 ;

这里再分析下触摸事件被消费之后的 , 触摸事件记录过程 ;

触摸事件如果成功被消费 , 则 dispatchTransformedTouchEvent 方法返回 true ;

对应的会调用 addTouchTarget 方法 , 创建 TouchTarget 对象 , 赋值给 newTouchTarget 成员变量 ;

newTouchTarget = addTouchTarget(child, idBitsToAssign)

TouchTarget 代表了个触摸事件 , 每个 TouchTarget 中都封装了消费该触摸事件的 View 组件 ;

        // The touched child view.// 当前 View 对象 public View child;

TouchTarget 经过优化后 , 以链表形式存储 , 每个 TouchTarget 都定义了一个 next 成员变量 , 指向下一个 TouchTarget 被消费的触摸事件 ;

        // The next target in the target list.// 链表操作 , 该引用指向下一个触摸事件 public TouchTarget next;

二、完整的触摸事件处理机制

完整触摸事件 :

一个完整的触摸动作 , 由 111 次按下触摸事件 , 若干次移动触摸事件 , 111 次抬起触摸事件组成 ,

111 个触摸动作只有 111 次按下操作 , 并且是整个触摸动作的起始触摸事件 ;

一个完整的动作 , 只有第一次按下 , 才执行子组件的排序 , 遍历 , 事件分发等操作 ; 第一次按下后 , 手指按着移动 , 属于第2次以及之后的第n次动作 , 不再走该分支 , 直接执行该分支后面的代码 ;

这里在第 111 次按下时 , 创建触摸事件记录 TouchTarget ; 假如当前动作时按下以后的移动/抬起动作 , 则跳过上面的分支 , 直接执行后面的代码逻辑 , 按下之后 mFirstTouchTarget 肯定不为空 ;

TouchTarget 事件记录封装 :

TouchTarget 对象对应着一个完整的动作 , 该动作包含 1 个按下事件 , 若干移动事件 , 1 个抬起事件 ;

第一次按下 , 负责构建 TouchTarget 链表 , 将消费事件的 View 组件封装到 TouchTarget 中 ;

然后的移动/抬起操作 , 不再重复的创建 TouchTarget 对象了 ; 直接使用第一次按下的 TouchTarget 对象作为当前动作的标识 , 直接向该 TouchTarget 对象中的 View 组件分发事件 ;

这也是我们按下按钮时 , 即使将手指按着移出边界 , 按钮也处于按下状态 ;

相关源码 :

public abstract class ViewGroup extends View implements ViewParent, ViewManager {// First touch target in the linked list of touch targets.private TouchTarget mFirstTouchTarget;@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {// 判断是否是按下操作 // 一个完整的动作 , 只有第一次按下 , 才执行下面的逻辑 // 第一次按下后 , 手指按着移动 , 属于第2次以及之后的第n次动作 , 不再走该分支 // 直接执行该分支后面的代码 if (actionMasked == MotionEvent.ACTION_DOWN|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {// 获取触摸索引值 final int actionIndex = ev.getActionIndex(); // always 0 for downfinal int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex): TouchTarget.ALL_POINTER_IDS;// 计算 ViewGroup 父容器下面有多少个子 View 组件 ; final int childrenCount = mChildrenCount;// TouchTarget newTouchTarget = null; 在上面声明为空 , 此处肯定为 null ; // childrenCount 子组件个数不为 0 // 如果子组件个数为 0 , 则不走下一段代码 , 如果子组件个数大于 0 , 则执行下一段代码 ; // 说明下面的代码块中处理的是 ViewGroup 中子组件的事件分发功能 ; if (newTouchTarget == null && childrenCount != 0) {// 获取单个手指的 x,y 坐标 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.// 子组件排序 , 按照 Z 轴排列的层级 , 从上到下进行排序 , // 控件会相互重叠 , Z 轴的排列次序上 , // 顶层的组件优先获取到触摸事件 final ArrayList<View> preorderedList = buildTouchDispatchChildList();final boolean customOrder = preorderedList == null&& isChildrenDrawingOrderEnabled();final View[] children = mChildren;// 倒序遍历 按照 Z 轴的上下顺序 , 排列好的组件 // 先遍历的 Z 轴方向上 , 放在最上面的组件 , 也就是顶层组件 for (int i = childrenCount - 1; i >= 0; i--) {// 获取索引final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);// 获取索引对应组件 final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);// If there is a view that has accessibility focus we want it// to get the event first and if not handled we will perform a// normal dispatch. We may do a double iteration but this is// safer given the timeframe.// 无障碍 辅助功能 if (childWithAccessibilityFocus != null) {if (childWithAccessibilityFocus != child) {continue;}childWithAccessibilityFocus = null;i = childrenCount - 1;}// X 控件范围 A , 如果手指按在 B 范围 , 不会触发 X 控件的事件 // 判定当前的组件是否可见 , 是否处于动画过程中 // ① canViewReceivePointerEvents 判定组件是否可见 , 会否处于动画 // ② isTransformedTouchPointInView 判定手指是否在控件上面 ; // 上述两种情况 , 不触发事件 if (!canViewReceivePointerEvents(child)|| !isTransformedTouchPointInView(x, y, child, null)) {ev.setTargetAccessibilityFocus(false);// 不触发事件 continue;}// 截止到此处 , 可以获取子组件进行操作   // 提取当前的子组件 // 第一次执行 getTouchTarget 代码时 , 是没有 mFirstTouchTarget 的// 此时第一次返回 null newTouchTarget = getTouchTarget(child);// 该分支操作第一次不执行 if (newTouchTarget != null) {// Child is already receiving touch within its bounds.// Give it the new pointer in addition to the ones it is handling.newTouchTarget.pointerIdBits |= idBitsToAssign;break;}resetCancelNextUpFlag(child);// 正式开始分发触摸事件// 处理以下两种情况 : // ① 情况一 : 子控件触摸事件返回 true // ② 情况二 : 子控件触摸事件返回 false if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {// Child wants to receive touch within its bounds.// 如果返回值为 true , 说明该事件已经被消费了 // 此时记录这个已经被消费的事件 mLastTouchDownTime = ev.getDownTime();if (preorderedList != null) {// childIndex points into presorted list, find original indexfor (int j = 0; j < childrenCount; j++) {if (children[childIndex] == mChildren[j]) {mLastTouchDownIndex = j;break;}}} else {mLastTouchDownIndex = childIndex;}mLastTouchDownX = ev.getX();mLastTouchDownY = ev.getY();// 记录消费事件 // 添加触摸目标 newTouchTarget = addTouchTarget(child, idBitsToAssign);alreadyDispatchedToNewTouchTarget = true;break;}// The accessibility focus didn't handle the event, so clear// the flag and do a normal dispatch to all children.ev.setTargetAccessibilityFocus(false);}if (preorderedList != null) preorderedList.clear();}// 上面的分支是只有第一次按下时才执行的 // 假如当前动作时按下以后的移动/抬起动作 // 则跳过上面的分支 , 直接执行后面的代码逻辑 // 按下之后 mFirstTouchTarget 肯定不为空 // 如果事件被消费 , 事件分发方法 dispatchTransformedTouchEvent 返回 true // 就会创建 newTouchTarget 值 , 该值不会为空 , 同时 mFirstTouchTarget 不为空// 反之// 如果上述事件分发方法 dispatchTransformedTouchEvent 返回 false // 此时 newTouchTarget 值 , 就会为空 , 同时 mFirstTouchTarget 为空 // // 还有一个逻辑就是 , 如果该事件被父容器拦截 , mFirstTouchTarget 也是 null 值// 调用 dispatchTransformedTouchEvent , 但是传入的子组件时 null // 在 dispatchTransformedTouchEvent 方法中触发调用 if (child == null) 分支的 // handled = super.dispatchTouchEvent(event) 方法 , 调用父类的事件分发方法 // Dispatch to touch targets.if (mFirstTouchTarget == null) {// 事件没有被消费的分支 // No touch targets so treat this as an ordinary view.handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);} else {// TouchTarget 对象对应着一个完整的动作 , 该动作包含 1 个按下事件 , 若干 移动 事件 , 1 个抬起事件 ; // 第一次按下 , 负责构建 TouchTarget 链表 , 将消费事件的 View 组件封装到 TouchTarget  中// 然后的移动/抬起操作 , 不再重复的创建 TouchTarget 对象了 // 直接使用第一次按下的 TouchTarget 对象作为当前动作的标识 // 直接向该 TouchTarget 对象中的 View 组件分发事件 // 这也是我们按下按钮时 , 即使将手指按着移出边界 , 按钮也处于按下状态 ; // 事件被消费的分支 , 事件消费成功 , 会走这个分支 // Dispatch to touch targets, excluding the new touch target if we already// dispatched to it.  Cancel touch targets if necessary.TouchTarget predecessor = null;// 将当前所有的消费的事件以及消费的 View 组件做成了一个链表 TouchTarget target = mFirstTouchTarget;while (target != null) {// 链表式操作 , 检索是哪个组件 , 然后开始分发 final TouchTarget next = target.next;if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {handled = true;} else {final boolean cancelChild = resetCancelNextUpFlag(target.child)|| intercepted;// 找到了 View , 开始分发触摸事件 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;}}}
}

三、ViewGroup | dispatchTouchEvent 方法返回

在【Android 事件分发】事件分发源码分析 ( Activity 中各层级的事件传递 | Activity -＞ PhoneWindow -＞ DecorView -＞ ViewGroup ) 博客中分析了从 Activity -＞ PhoneWindow -＞ DecorView -＞ ViewGroup 的调用链 ;

ViewGroup 的 dispatchTouchEvent 事件分发方法执行完毕后 ,
先返回到 DecorView | superDispatchTouchEvent 方法 ,
然后返回到 PhoneWindow | superDispatchTouchEvent 方法 .
最终返回到 Activity 的 dispatchTouchEvent ;

如果在 Activity 的 dispatchTouchEvent 方法中 , PhoneWindow 的 superDispatchTouchEvent 方法的返回值是 true , 即 ViewGroup 的 dispatchTouchEvent 方法返回 true ;

则直接返回 , 不再向后执行 ;

     // getWindow() 获取的是 PhoneWindow 窗口 // 调用 PhoneWindow 的 superDispatchTouchEvent ; if (getWindow().superDispatchTouchEvent(ev)) {return true;}

相关源码 :

public class Activity extends ContextThemeWrapperimplements LayoutInflater.Factory2,Window.Callback, KeyEvent.Callback,OnCreateContextMenuListener, ComponentCallbacks2,Window.OnWindowDismissedCallback, WindowControllerCallback,AutofillManager.AutofillClient {/*** Called to process touch screen events.  You can override this to* intercept all touch screen events before they are dispatched to the* window.  Be sure to call this implementation for touch screen events* that should be handled normally.** @param ev The touch screen event.** @return boolean Return true if this event was consumed.*/public boolean dispatchTouchEvent(MotionEvent ev) {if (ev.getAction() == MotionEvent.ACTION_DOWN) {// 判定是否是第一次按下 // 该方法与事件传递机制流程无关 // 提供给用户按下时可以执行的业务逻辑 onUserInteraction();}// getWindow() 获取的是 PhoneWindow 窗口 // 调用 PhoneWindow 的 superDispatchTouchEvent ; if (getWindow().superDispatchTouchEvent(ev)) {return true;}return onTouchEvent(ev);}public void onUserInteraction() {}
}

源码路径 : /frameworks/base/core/java/android/app/Activity.java

四、ViewGroup 事件分发相关源码

@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {// First touch target in the linked list of touch targets.private TouchTarget mFirstTouchTarget;@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {// 辅助功能 , 残疾人相关辅助 , 跨进程调用 无障碍 功能if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onTouchEvent(ev, 1);}// If the event targets the accessibility focused view and this is it, start// normal event dispatch. Maybe a descendant is what will handle the click.// 判断产生事件的目标组件是可访问性的 , 那么按照普通的事件分发进行处理 ; // 可能由其子类处理点击事件 ; // 判断当前是否正在使用 无障碍 相关功能产生事件 if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {ev.setTargetAccessibilityFocus(false);}// 是否按下操作 , 最终的对外返回结果 , 该方法的最终返回值 boolean handled = false;if (onFilterTouchEventForSecurity(ev)) {final int action = ev.getAction();final int actionMasked = action & MotionEvent.ACTION_MASK;// 第一步 : 判断是否是按下操作 // Handle an initial down.// 判断是否是第一次按下 , 如果是第一次按下 , 则执行下面的业务逻辑 if (actionMasked == MotionEvent.ACTION_DOWN) {// Throw away all previous state when starting a new touch gesture.// The framework may have dropped the up or cancel event for the previous gesture// due to an app switch, ANR, or some other state change.cancelAndClearTouchTargets(ev);// 如果是第一次按下 , 那么重置触摸状态 resetTouchState();}// 第二步 : 判断是否需要拦截 , 用户使用 requestDisallowInterceptTouchEvent 方法进行设置是否拦截事件// Check for interception.// 判定是否拦截 // 用于多点触控按下操作的判定 final boolean intercepted;if (actionMasked == MotionEvent.ACTION_DOWN|| mFirstTouchTarget != null) {// 判断是否需要拦截 , 可以使用 requestDisallowInterceptTouchEvent 方法进行设置final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;if (!disallowIntercept) {// 进行事件拦截 // 该 onInterceptTouchEvent 方法只返回是否进行事件拦截 , 返回一个布尔值 , 没有进行具体的事件拦截 // 是否进行拦截 , 赋值给了 intercepted 局部变量 // 该值决定是否进行拦截 intercepted = onInterceptTouchEvent(ev);ev.setAction(action); // restore action in case it was changed} else {// 不进行事件拦截 intercepted = false;}} else {// There are no touch targets and this action is not an initial down// so this view group continues to intercept touches.intercepted = true;}// If intercepted, start normal event dispatch. Also if there is already// a view that is handling the gesture, do normal event dispatch.if (intercepted || mFirstTouchTarget != null) {ev.setTargetAccessibilityFocus(false);}// 第三步 : 判定该动作是否是取消动作 , 手指移出组件边界范围就是取消事件 ; // Check for cancelation.// 检查是否取消操作 , 手指是否移除了组件便捷 ; // 一般情况默认该值是 false ; final boolean canceled = resetCancelNextUpFlag(this)|| actionMasked == MotionEvent.ACTION_CANCEL;// Update list of touch targets for pointer down, if needed.final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;// 注意此处 newTouchTarget 为空 TouchTarget newTouchTarget = null;boolean alreadyDispatchedToNewTouchTarget = false;// 第四步 : 判定是否拦截事件 , 以及是否取消事件 , 如果都为否 //         即不拦截事件 , 该事件也不取消 , 则执行该分支 //            在该分支中 , 记录该触摸事件 // 此处判定 , 是否拦截 // 假定不取消 , 也不拦截 // canceled 和 intercepted 二者都是 false , 才不能拦截 ; if (!canceled && !intercepted) {// If the event is targeting accessibility focus we give it to the// view that has accessibility focus and if it does not handle it// we clear the flag and dispatch the event to all children as usual.// We are looking up the accessibility focused host to avoid keeping// state since these events are very rare.// 无障碍 辅助功能 View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()? findChildWithAccessibilityFocus() : null;// 第五步 : 判定是否是按下操作 , 如果是 , 则记录该事件 , 如果不是 , 则不执行该分支// 判断是否是按下操作 // 一个完整的动作 , 只有第一次按下 , 才执行下面的逻辑 // 第一次按下后 , 手指按着移动 , 属于第2次以及之后的第n次动作 , 不再走该分支 // 直接执行该分支后面的代码 if (actionMasked == MotionEvent.ACTION_DOWN|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {// 获取触摸索引值 final int actionIndex = ev.getActionIndex(); // always 0 for downfinal int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex): TouchTarget.ALL_POINTER_IDS;// Clean up earlier touch targets for this pointer id in case they// have become out of sync.removePointersFromTouchTargets(idBitsToAssign);// 计算 ViewGroup 父容器下面有多少个子 View 组件 ; final int childrenCount = mChildrenCount;// TouchTarget newTouchTarget = null; 在上面声明为空 , 此处肯定为 null ; // childrenCount 子组件个数不为 0 // 如果子组件个数为 0 , 则不走下一段代码 , 如果子组件个数大于 0 , 则执行下一段代码 ; // 说明下面的代码块中处理的是 ViewGroup 中子组件的事件分发功能 ; if (newTouchTarget == null && childrenCount != 0) {// 获取单个手指的 x,y 坐标 final float x = ev.getX(actionIndex);final float y = ev.getY(actionIndex);// 第六步 : 对子控件进行排序 // Find a child that can receive the event.// Scan children from front to back.// 子组件排序 , 按照 Z 轴排列的层级 , 从上到下进行排序 , // 控件会相互重叠 , Z 轴的排列次序上 , // 顶层的组件优先获取到触摸事件 final ArrayList<View> preorderedList = buildTouchDispatchChildList();final boolean customOrder = preorderedList == null&& isChildrenDrawingOrderEnabled();final View[] children = mChildren;// 第七步 : 倒序遍历 , 取顶层组件// 倒序遍历 按照 Z 轴的上下顺序 , 排列好的组件 // 先遍历的 Z 轴方向上 , 放在最上面的组件 , 也就是顶层组件 for (int i = childrenCount - 1; i >= 0; i--) {// 获取索引final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);// 获取索引对应组件 final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);// If there is a view that has accessibility focus we want it// to get the event first and if not handled we will perform a// normal dispatch. We may do a double iteration but this is// safer given the timeframe.// 无障碍 辅助功能 if (childWithAccessibilityFocus != null) {if (childWithAccessibilityFocus != child) {continue;}childWithAccessibilityFocus = null;i = childrenCount - 1;}// 第八步 : 判定当前事件是否可用 , 组件可见 , 不处于动画阶段 , 手指在组件范围中// X 控件范围 A , 如果手指按在 B 范围 , 不会触发 X 控件的事件 // 判定当前的组件是否可见 , 是否处于动画过程中 // ① canViewReceivePointerEvents 判定组件是否可见 , 会否处于动画 // ② isTransformedTouchPointInView 判定手指是否在控件上面 ; // 上述两种情况 , 不触发事件 if (!canViewReceivePointerEvents(child)|| !isTransformedTouchPointInView(x, y, child, null)) {ev.setTargetAccessibilityFocus(false);// 不触发事件 continue;}// 截止到此处 , 可以获取子组件进行操作   // 提取当前的子组件 // 第一次执行 getTouchTarget 代码时 , 是没有 mFirstTouchTarget 的// 此时第一次返回 null newTouchTarget = getTouchTarget(child);// 该分支操作第一次不执行 if (newTouchTarget != null) {// Child is already receiving touch within its bounds.// Give it the new pointer in addition to the ones it is handling.newTouchTarget.pointerIdBits |= idBitsToAssign;break;}resetCancelNextUpFlag(child);// 第九步 : 正式向子组件分发触摸事件//           如果分发事件被消耗掉 , 返回 true , 则记录该事件//             记录事件调用的 addTouchTarget 方法中 , 为 mFirstTouchTarget 成员变量赋值 //          如果分发事件没有被消耗掉 , 返回 false // 正式开始分发触摸事件// 处理以下两种情况 : // ① 情况一 : 子控件触摸事件返回 true // ② 情况二 : 子控件触摸事件返回 false if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {// Child wants to receive touch within its bounds.// 如果返回值为 true , 说明该事件已经被消费了 // 此时记录这个已经被消费的事件 mLastTouchDownTime = ev.getDownTime();if (preorderedList != null) {// childIndex points into presorted list, find original indexfor (int j = 0; j < childrenCount; j++) {if (children[childIndex] == mChildren[j]) {mLastTouchDownIndex = j;break;}}} else {mLastTouchDownIndex = childIndex;}mLastTouchDownX = ev.getX();mLastTouchDownY = ev.getY();// 记录消费事件 // 添加触摸目标 newTouchTarget = addTouchTarget(child, idBitsToAssign);alreadyDispatchedToNewTouchTarget = true;break;}// The accessibility focus didn't handle the event, so clear// the flag and do a normal dispatch to all children.ev.setTargetAccessibilityFocus(false);}if (preorderedList != null) preorderedList.clear();}// 如果上述事件分发方法 dispatchTransformedTouchEvent 返回 true // 就会创建 newTouchTarget 值 , 该值不会为空 , 同时 mFirstTouchTarget 不为空// 如果上述事件分发方法 dispatchTransformedTouchEvent 返回 false // 此时 newTouchTarget 值 , 就会为空 , 同时 mFirstTouchTarget 为空 if (newTouchTarget == null && mFirstTouchTarget != null) {// Did not find a child to receive the event.// Assign the pointer to the least recently added target.newTouchTarget = mFirstTouchTarget;while (newTouchTarget.next != null) {newTouchTarget = newTouchTarget.next;}newTouchTarget.pointerIdBits |= idBitsToAssign;}}}// 第十步 : 判定当前是否有消费记录 , 即 Down 按下事件是否执行完毕//            如果有事件消费记录则 mFirstTouchTarget 成员不为空 , 此时从 TouchTarget 链表中取出相应的消费 Down 事件组件 , 直接将事件分发给该组件//           如果没有事件消费记录 , 则 mFirstTouchTarget 成员为空 , 此时调用 dispatchTransformedTouchEvent 方法消费自己 ; // 上面的分支是只有第一次按下时才执行的 // 假如当前动作时按下以后的移动/抬起动作 // 则跳过上面的分支 , 直接执行后面的代码逻辑 // 按下之后 mFirstTouchTarget 肯定不为空 // 如果事件被消费 , 事件分发方法 dispatchTransformedTouchEvent 返回 true // 就会创建 newTouchTarget 值 , 该值不会为空 , 同时 mFirstTouchTarget 不为空// 反之// 如果上述事件分发方法 dispatchTransformedTouchEvent 返回 false // 此时 newTouchTarget 值 , 就会为空 , 同时 mFirstTouchTarget 为空 // // 还有一个逻辑就是 , 如果该事件被父容器拦截 , mFirstTouchTarget 也是 null 值// 调用 dispatchTransformedTouchEvent , 但是传入的子组件时 null // 在 dispatchTransformedTouchEvent 方法中触发调用 if (child == null) 分支的 // handled = super.dispatchTouchEvent(event) 方法 , 调用父类的事件分发方法 // Dispatch to touch targets.if (mFirstTouchTarget == null) {// 事件没有被消费的分支 // No touch targets so treat this as an ordinary view.handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);} else {// TouchTarget 对象对应着一个完整的动作 , 该动作包含 1 个按下事件 , 若干 移动 事件 , 1 个抬起事件 ; // 第一次按下 , 负责构建 TouchTarget 链表 , 将消费事件的 View 组件封装到 TouchTarget  中// 然后的移动/抬起操作 , 不再重复的创建 TouchTarget 对象了 // 直接使用第一次按下的 TouchTarget 对象作为当前动作的标识 // 直接向该 TouchTarget 对象中的 View 组件分发事件 // 这也是我们按下按钮时 , 即使将手指按着移出边界 , 按钮也处于按下状态 ; // 事件被消费的分支 , 事件消费成功 , 会走这个分支 // Dispatch to touch targets, excluding the new touch target if we already// dispatched to it.  Cancel touch targets if necessary.TouchTarget predecessor = null;// 将当前所有的消费的事件以及消费的 View 组件做成了一个链表 TouchTarget target = mFirstTouchTarget;while (target != null) {// 链表式操作 , 检索是哪个组件 , 然后开始分发 final TouchTarget next = target.next;if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {handled = true;} else {final boolean cancelChild = resetCancelNextUpFlag(target.child)|| intercepted;// 找到了 View , 开始分发触摸事件 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;}}// Update list of touch targets for pointer up or cancel, if needed.// 移动取消相关逻辑 if (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);}}if (!handled && mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);}// ViewGroup 的 事件分发方法执行完毕后 // 返回到 Activity 的 dispatchTouchEvent return handled;}/* Describes a touched view and the ids of the pointers that it has captured.** This code assumes that pointer ids are always in the range 0..31 such that* it can use a bitfield to track which pointer ids are present.* As it happens, the lower layers of the input dispatch pipeline also use the* same trick so the assumption should be safe here...* 可以理解成触摸事件的消费目标 */private static final class TouchTarget {private static final int MAX_RECYCLED = 32;private static final Object sRecycleLock = new Object[0];private static TouchTarget sRecycleBin;private static int sRecycledCount;public static final int ALL_POINTER_IDS = -1; // all ones// The touched child view.// 当前 View 对象 public View child;// The combined bit mask of pointer ids for all pointers captured by the target.public int pointerIdBits;// The next target in the target list.// 链表操作 , 该引用指向下一个触摸事件 public TouchTarget next;private TouchTarget() {}public static TouchTarget obtain(@NonNull View child, int pointerIdBits) {if (child == null) {throw new IllegalArgumentException("child must be non-null");}final TouchTarget target;synchronized (sRecycleLock) {if (sRecycleBin == null) {target = new TouchTarget();} else {target = sRecycleBin;sRecycleBin = target.next;sRecycledCount--;target.next = null;}}target.child = child;target.pointerIdBits = pointerIdBits;return target;}public void recycle() {if (child == null) {throw new IllegalStateException("already recycled once");}synchronized (sRecycleLock) {if (sRecycledCount < MAX_RECYCLED) {next = sRecycleBin;sRecycleBin = this;sRecycledCount += 1;} else {next = null;}child = null;}}}@Overridepublic void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {// disallowIntercept 存在一个默认值 , 如果值为默认值 , 直接退出 if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) {// We're already in this state, assume our ancestors are tooreturn;}// 如果不是默认值 , 则进行相应更改 // 最终的值影响 mGroupFlags 是 true 还是 false if (disallowIntercept) {mGroupFlags |= FLAG_DISALLOW_INTERCEPT;} else {mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;}// Pass it up to our parentif (mParent != null) {mParent.requestDisallowInterceptTouchEvent(disallowIntercept);}}public boolean onInterceptTouchEvent(MotionEvent ev) {// 该方法只返回是否进行事件拦截 , 返回一个布尔值 , 没有进行具体的事件拦截 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;}/*** Provide custom ordering of views in which the touch will be dispatched.* 按照事件传递的顺序进行组件排序 ** This is called within a tight loop, so you are not allowed to allocate objects, including* the return array. Instead, you should return a pre-allocated list that will be cleared* after the dispatch is finished.* @hide*/public ArrayList<View> buildTouchDispatchChildList() {return buildOrderedChildList();}/*** Populates (and returns) mPreSortedChildren with a pre-ordered list of the View's children,* sorted first by Z, then by child drawing order (if applicable). This list must be cleared* after use to avoid leaking child Views.** Uses a stable, insertion sort which is commonly O(n) for ViewGroups with very few elevated* children.*/ArrayList<View> buildOrderedChildList() {final int childrenCount = mChildrenCount;if (childrenCount <= 1 || !hasChildWithZ()) return null;if (mPreSortedChildren == null) {mPreSortedChildren = new ArrayList<>(childrenCount);} else {// callers should clear, so clear shouldn't be necessary, but for safety...mPreSortedChildren.clear();mPreSortedChildren.ensureCapacity(childrenCount);}final boolean customOrder = isChildrenDrawingOrderEnabled();// 下面的组件排序的核心逻辑 // 获取当前所有组件的子组件的 Z 轴的深度 // 按照 Z 轴深度进行排序 // Z 轴方向上 , 对于事件传递 , 上面的组件优先级高于被覆盖的下面的组件优先级for (int i = 0; i < childrenCount; i++) {// add next child (in child order) to end of listfinal int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);final View nextChild = mChildren[childIndex];final float currentZ = nextChild.getZ();// insert ahead of any Views with greater Z// 计算当前遍历的组件应该被放到的索引位置int insertIndex = i;while (insertIndex > 0 && mPreSortedChildren.get(insertIndex - 1).getZ() > currentZ) {insertIndex--;}// 将当前遍历的组件插入到指定索引位置上 mPreSortedChildren.add(insertIndex, nextChild);}return mPreSortedChildren;}// 获取排序后的子组件的索引值private int getAndVerifyPreorderedIndex(int childrenCount, int i, boolean customOrder) {final int childIndex;if (customOrder) {final int childIndex1 = getChildDrawingOrder(childrenCount, i);if (childIndex1 >= childrenCount) {throw new IndexOutOfBoundsException("getChildDrawingOrder() "+ "returned invalid index " + childIndex1+ " (child count is " + childrenCount + ")");}childIndex = childIndex1;} else {childIndex = i;}return childIndex;}// 获取索引值对应的组件 private static View getAndVerifyPreorderedView(ArrayList<View> preorderedList, View[] children,int childIndex) {final View child;if (preorderedList != null) {child = preorderedList.get(childIndex);if (child == null) {throw new RuntimeException("Invalid preorderedList contained null child at index "+ childIndex);}} else {child = children[childIndex];}return child;}/*** Returns true if a child view can receive pointer events.* 判定控件是否可见 / 是否处于动画中 * @hide*/private static boolean canViewReceivePointerEvents(@NonNull View child) {return (child.mViewFlags & VISIBILITY_MASK) == VISIBLE|| child.getAnimation() != null;}/*** Returns true if a child view contains the specified point when transformed* into its coordinate space.* Child must not be null.* 判定手指是否触摸到了组件 , 是否在组件区域范围内 * @hide*/protected boolean isTransformedTouchPointInView(float x, float y, View child,PointF outLocalPoint) {// 获取当前坐标 final float[] point = getTempPoint();point[0] = x;point[1] = y;transformPointToViewLocal(point, child);final boolean isInView = child.pointInView(point[0], point[1]);if (isInView && outLocalPoint != null) {outLocalPoint.set(point[0], point[1]);}return isInView;}/*** Gets the touch target for specified child view.* Returns null if not found.* */private TouchTarget getTouchTarget(@NonNull View child) {// 判断 mFirstTouchTarget 中的 child 字段 , 是否是当前遍历的 子组件 View // 如果是 , 则返回该 TouchTarget // 如果不是 , 则返回空for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) {if (target.child == child) {return target;}}return null;}/*** 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.* 该方法是正式分发触摸事件的方法 * 注意参数中传入了当前正在被遍历的 child 子组件 */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.// 处理取消状态 , 暂时不分析 ; 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) {// 被遍历的 child 子组件为空 // 调用父类的分发方法 handled = super.dispatchTouchEvent(event);} else {// 被遍历的 child 子组件不为空 final float offsetX = mScrollX - child.mLeft;final float offsetY = mScrollY - child.mTop;event.offsetLocation(offsetX, offsetY);// 子组件分发触摸事件 // 此处调用的是 View 组件的 dispatchTouchEvent 方法 ; 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) {handled = 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;}/*** Adds a touch target for specified child to the beginning of the list.* Assumes the target child is not already present.*/private TouchTarget addTouchTarget(@NonNull View child, int pointerIdBits) {final TouchTarget target = TouchTarget.obtain(child, pointerIdBits);target.next = mFirstTouchTarget;mFirstTouchTarget = target;return target;}@Overridepublic void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {// 设置父容器是否要拦截子组件的触摸事件if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) {// We're already in this state, assume our ancestors are tooreturn;}if (disallowIntercept) {mGroupFlags |= FLAG_DISALLOW_INTERCEPT;} else {mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;}// Pass it up to our parentif (mParent != null) {mParent.requestDisallowInterceptTouchEvent(disallowIntercept);}}}

五、View 事件分发相关源码

public class View implements Drawable.Callback, KeyEvent.Callback,AccessibilityEventSource {/*** 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) {// 无障碍调用 , 辅助功能 // 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);}// 返回结果 boolean result = false;if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onTouchEvent(event, 0);}// 判定手指的动作 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;}//noinspection SimplifiableIfStatement// 设置的 触摸监听器 就是封装在该对象中 ListenerInfo li = mListenerInfo;// 判断该组件是否被用户设置了 触摸监听器 OnTouchListenerif (li != null && li.mOnTouchListener != null&& (mViewFlags & ENABLED_MASK) == ENABLED// 执行被用户设置的 触摸监听器 OnTouchListener&& li.mOnTouchListener.onTouch(this, event)) {// 如果用户设置的 触摸监听器 OnTouchListener 触摸方法返回 true// 此时该分发方法的返回值就是 true result = true;}// 如果上面为 true ( 触摸监听器的触摸事件处理返回 true ) , 就会阻断该分支的命中 , 该分支不执行了 // 也就不会调用 View 组件自己的 onTouchEvent 方法 // 因此 , 如果用户的 触摸监听器 OnTouchListener 返回 true // 则 用户的 点击监听器 OnClickListener 会被屏蔽掉 // 如果同时设置了 点击监听器 OnClickListener 和 触摸监听器 OnTouchListener // 触摸监听器 OnTouchListener 返回 false , 点击监听器 OnClickListener 才能被调用到 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;}/*** Implement this method to handle touch screen motion events.* <p>* If this method is used to detect click actions, it is recommended that* the actions be performed by implementing and calling* {@link #performClick()}. This will ensure consistent system behavior,* including:* <ul>* <li>obeying click sound preferences* <li>dispatching OnClickListener calls* <li>handling {@link AccessibilityNodeInfo#ACTION_CLICK ACTION_CLICK} when* accessibility features are enabled* </ul>** @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();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:// 点击事件 Click 是 按下 + 抬起 事件 // 如果要判定点击 , 需要同时有 MotionEvent.ACTION_DOWN + MotionEvent.ACTION_UP 事件 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) {// 此处创建点击对象 mPerformClick = new PerformClick();}// 调用点击事件 if (!post(mPerformClick)) {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);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;}/*** Entry point for {@link #performClick()} - other methods on View should call it instead of* {@code performClick()} directly to make sure the autofill manager is notified when* necessary (as subclasses could extend {@code performClick()} without calling the parent's* method).*/private boolean performClickInternal() {// Must notify autofill manager before performing the click actions to avoid scenarios where// the app has a click listener that changes the state of views the autofill service might// be interested on.notifyAutofillManagerOnClick();return performClick();}/*** Call this view's OnClickListener, if it is defined.  Performs all normal* actions associated with clicking: reporting accessibility event, playing* a sound, etc.** @return True there was an assigned OnClickListener that was called, false*         otherwise is returned.*/// NOTE: other methods on View should not call this method directly, but performClickInternal()// instead, to guarantee that the autofill manager is notified when necessary (as subclasses// could extend this method without calling super.performClick()).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);// 此处直接执行了 点击监听器 的点击方法 li.mOnClickListener.onClick(this);result = true;} else {result = false;}sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);notifyEnterOrExitForAutoFillIfNeeded(true);return result;}}

源码路径 : /frameworks/base/core/java/android/view/View.java

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Android 事件分发系列文章目录

文章目录

一、按下触摸事件记录

二、完整的触摸事件处理机制

三、ViewGroup | dispatchTouchEvent 方法返回

四、ViewGroup 事件分发相关源码

五、View 事件分发相关源码

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文章目录

一、按下触摸事件记录

二、完整的触摸事件处理机制

三、ViewGroup | dispatchTouchEvent 方法返回

四、ViewGroup 事件分发相关源码

五、View 事件分发相关源码

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