Android 点击事件图示源码解析

Android 点击事件图示源码解析

前言

仅用于知识点简介，详细描述建议百度，主要是一些个人的理解总结，可以在面试时来回答，所以并不是很详细，只是总结~

Android 点击事件

1. 传递过程

1. 分发流程：Activity -> Window -> DecorView -> ViewGroup… -> View
2. 消费流程：View -> ViewGroup… -> DecorView -> Window -> Activity

2. 图示

3. 源码解释

3.1 代码1 - Activity.dispatchTouchEvent

public boolean dispatchTouchEvent(MotionEvent ev) {if (ev.getAction() == MotionEvent.ACTION_DOWN) {// 点击事件会在 onUserInteraction 通知onUserInteraction();}// 向 Window 分发if (getWindow().superDispatchTouchEvent(ev)) {// 如果消耗 则 返回 truereturn true;}// Window 下均未消耗，则自己处理 onTouchEvent()return onTouchEvent(ev);
}

3.2 代码2 - ViewGroup.dispatchTouchEvent

public boolean dispatchTouchEvent(MotionEvent ev) {...// 检查是否拦截final boolean intercepted;if (actionMasked == MotionEvent.ACTION_DOWN|| mFirstTouchTarget != null) {// 是否禁止拦截final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;if (!disallowIntercept) {// 未禁止拦截，调用 onInterceptTouchEvent 检查是否拦截intercepted = onInterceptTouchEvent(ev);// 重新载入 action，所以在 onInterceptTouchEvent 中 ev 的 action 的变更是不会生效的ev.setAction(action); } else {intercepted = false;}} else {// 如果没有触摸目标 touchTarget 且 不是 Down 事件，那么说明从 Down 事件就与本视图无关，不关注后续事件，所以直接屏蔽// 这也是为什么如果拦截了 Down 事件，那么后续的事件都收不到intercepted = true;}...if (!canceled && !intercepted) {...TouchTarget newTouchTarget = null;boolean alreadyDispatchedToNewTouchTarget = false;for (int i = childrenCount - 1; i >= 0; i--) {if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {// 检查点击范围内的 childmLastTouchDownTime = 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();// 添加到     mFirstTouchTargetnewTouchTarget = addTouchTarget(child, idBitsToAssign);alreadyDispatchedToNewTouchTarget = true;break;}}}...if (mFirstTouchTarget == null) {// 没有找到点击目标，自己处理点击事件handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);} else {// 根据 mFirstTouchTarget 逐级发放点击事件，根据需要向其中的 target 发放 cancel 事件TouchTarget predecessor = null;TouchTarget target = mFirstTouchTarget;while (target != null) {final TouchTarget next = ;if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {handled = true;} else {final boolean cancelChild = resetCancelNextUpFlag(target.child)|| intercepted;// 发放事件if (dispatchTransformedTouchEvent(ev, cancelChild,target.child, target.pointerIdBits)) {handled = true;}if (cancelChild) {if (predecessor == null) {mFirstTouchTarget = next;} else { = next;}le();target = next;continue;}}predecessor = target;target = next;}}...return true;
}

3.3 代码3 - View.dispatchTouchEvent

public boolean dispatchTouchEvent(MotionEvent event) {boolean result = false;...if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {// 处理滚动result = true;}ListenerInfo li = mListenerInfo;if (li != null && li.mOnTouchListener != null&& (mViewFlags & ENABLED_MASK) == ENABLED&& Touch(this, event)) {// 有 mOnTouchListener，且Touch 返回 true 消耗了事件result = true;}if (!result && onTouchEvent(event)) {// 如果之前的操作没有消耗事件，则会调用自己的 onTouchEvent 处理事件result = true;}...return result;
}