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 )
文章目录
- Android 事件分发 系列文章目录
- 前言
- 一、ViewGroup | dispatchTransformedTouchEvent 方法返回值含义
- 二、记录被消费的触摸事件
- 三、触摸事件没有被消费的调用链分析
- 四、触摸事件被拦截的调用链分析
- 五、ViewGroup 事件分发相关源码
- 六、View 事件分发相关源码
- 总结
前言
接上一篇博客 【Android 事件分发】事件分发源码分析 ( View 事件传递机制 ) , 继续分析 ViewGroup 的事件分发机制后续代码 ;
Activity 事件传递 , 最终调用到了 ViewGroup 的 dispatchTouchEvent 方法 , 在该方法中有调用了 View 的 dispatchTouchEvent 方法 ;
View 的 dispatchTouchEvent 调用完毕后 , 会返回 true 或 false 结果 ；
那么继续回到 ViewGroup 的 dispatchTransformedTouchEvent 方法 , 在该方法中 , 也就是遍历 ViewGroup 子组件时 , 调用遍历的子组件 View 的 dispatchTouchEvent 方法 , 处理相关触摸和点击相关的操作 ;
本博客继续分析 ViewGroup 的后续调用链 ;
一、ViewGroup | dispatchTransformedTouchEvent 方法返回值含义
在 ViewGroup | dispatchTouchEvent 方法中 , 调用 ViewGroup | dispatchTransformedTouchEvent 方法进行事件的转发 , 主要是遍历子组件调用子组件的触摸方法 ;
在 ViewGroup | dispatchTransformedTouchEvent 方法中 , 调用了 View 子组件的 View | dispatchTouchEvent 方法 , 该方法返回 true/false , 那么对应的 ViewGroup | dispatchTransformedTouchEvent 方法也会返回相同的值 ;
由下面的代码可知 , handled 是子组件 child.dispatchTouchEvent 调用返回值 , 返回结果就是 handled , 然后有将该值直接返回 , 说明 View 子组件的 dispatchTouchEvent 调用结果 , 就是 ViewGroup 的 dispatchTransformedTouchEvent 方法的返回结果 ;
ViewGroup | dispatchTransformedTouchEvent 方法的返回值含义 :
① 如果返回 true , 证明 子组件 View 已经将事件消费完毕 , 后续不需要再继续执行遍历了 ;
② 如果返回 false , 证明 子组件并没有将事件消费 , 后续还可以进行触发 ;
代码语言：javascript复制public abstract class ViewGroup extends View implements ViewParent, ViewManager {
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
...
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;
}
...
}
}二、记录被消费的触摸事件
如果 ViewGroup | dispatchTransformedTouchEvent 方法的返回值为 true , 则会触发记录已经被消费的事件的分支 ; 如果返回 false , 则不会触发 ;
代码语言：javascript复制// 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)) {记录时 , 同时会创建 TouchTarget , 并赋值给 ViewGroup | dispatchTouchEvent | newTouchTarget 局部变量 ;
代码语言：javascript复制// 记录消费事件
// 添加触摸目标
newTouchTarget = addTouchTarget(child, idBitsToAssign);调用 addTouchTarget 方法 , 创建被消费的事件 , 并将创建的值赋值给了 ViewGroup | mFirstTouchTarget 成员 ; 第一次消费事件被赋值 ;
代码语言：javascript复制 private TouchTarget addTouchTarget(@NonNull View child, int pointerIdBits) {
final TouchTarget target = TouchTarget.obtain(child, pointerIdBits);
target.next = mFirstTouchTarget;
mFirstTouchTarget = target;
return target;
}完整代码如下 :
代码语言：javascript复制@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
...
// 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 index
for (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();
...
}
/**
* 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;
}
}三、触摸事件没有被消费的调用链分析
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 ;
如果 ViewGroup | dispatchTransformedTouchEvent 方法的返回值为 false , 则不会记录事件消费 ; 也就不会调用 ViewGroup | addTouchTarget 方法 , 此时
ViewGroup | dispatchTouchEvent | newTouchTarget 局部变量
ViewGroup | mFirstTouchTarget 成员变量
为空 ;
代码语言：javascript复制 /**
* 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;
}当执行到 if (mFirstTouchTarget == null) 分支时 , 会命中该分支 , 进而调用 dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS) 方法 , 在 dispatchTransformedTouchEvent 方法中 , 如果 child 为空 , 则会调用父类的 super.dispatchTouchEvent 方法 ;
@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
...
// 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 index
for (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();
// Dispatch to touch targets.
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
}
...
}
/**
* 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;
}
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
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;
}
...
}
}ViewGroup 继承自 View , 在 ViewGroup 中调用 super.dispatchTouchEvent 方法 , 就是调用 View 的 dispatchTouchEvent 方法 ;
super.dispatchTouchEvent(event) 方法消费的是父容器自己的事件 ;
child.dispatchTouchEvent(event) 方法消费的是子组件的事件 ;
四、触摸事件被拦截的调用链分析
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 ;
假设事件已经被消费了 , if (newTouchTarget == null && mFirstTouchTarget != null) 分支的代码不会被命中 , 继续向下分析 ;
同理如果事件被消费 , 也不会命中 if (mFirstTouchTarget == null) 分支 ;
下面讨论另外一种情况 , 就是父容器拦截触摸事件 ;
调用 ViewGroup | requestDisallowInterceptTouchEvent 可以设置是否拦截触摸事件 , 如果传入 true 则拦截触摸事件 , 如果传入 false , 则不拦截触摸事件 ;
在该 ViewGroup | requestDisallowInterceptTouchEvent 方法中 , 会修改 mGroupFlags 值 ;
代码语言：javascript复制 @Override
public 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 too
return;
}
if (disallowIntercept) {
mGroupFlags |= FLAG_DISALLOW_INTERCEPT;
} else {
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
}
// Pass it up to our parent
if (mParent != null) {
mParent.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}在 ViewGroup | dispatchTouchEvent 方法中 , 通过 mGroupFlags & FLAG_DISALLOW_INTERCEPT 判定父容器是否需要拦截子组件的触摸事件 , 该值最终影响 ViewGroup | dispatchTouchEvent | intercepted 局部变量的判断 ;
// Check for interception.
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
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;
}假如父容器要拦截事件 , 此时 intercepted 值为 true , if (!canceled && !intercepted) { 分支就不会被命中 , 该分支是事件分发的核心逻辑 , 全都被屏蔽了 , 最终 :
ViewGroup | dispatchTouchEvent | newTouchTarget 局部变量
ViewGroup | mFirstTouchTarget 成员变量
都为空 , 执行到 if (mFirstTouchTarget == null) 分支时 , 会命中该分支 , 进而调用 dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS) 方法 , 在 dispatchTransformedTouchEvent 方法中 , 如果 child 为空 , 则会调用父类的 super.dispatchTouchEvent 方法 ;
ViewGroup 继承自 View , 在 ViewGroup 中调用 super.dispatchTouchEvent 方法 , 就是调用 View 的 dispatchTouchEvent 方法 ;
super.dispatchTouchEvent(event) 方法消费的是父容器自己的事件 ;
child.dispatchTouchEvent(event) 方法消费的是子组件的事件 ;
代码语言：javascript复制 private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
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;
}
...
}ViewGroup | dispatchTouchEvent 相关代码 :
代码语言：javascript复制@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
...
// 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;
}
}
}
// 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);
}
...
}
/**
* 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;
}
/**
* 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.
*/
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;
}
...
}
}五、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;
@Override
public 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;
// 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();
}
// 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);
}
// 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;
// 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;
// 判断是否是按下操作
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 down
final 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);
// 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 index
for (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;
}
}
}
// 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 {
// 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;
//
TouchTarget target = mFirstTouchTarget;
while (target != null) {
// 链表式操作
final TouchTarget next = target.next;
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
// 转发下一个触摸事件
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.
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);
}
return handled;
}
@Override
public 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 too
return;
}
// 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 parent
if (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 list
final 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;
}
@Override
public 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 too
return;
}
if (disallowIntercept) {
mGroupFlags |= FLAG_DISALLOW_INTERCEPT;
} else {
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
}
// Pass it up to our parent
if (mParent != null) {
mParent.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}
}六、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 gesture
stopNestedScroll();
}
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 OnTouchListener
if (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 check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!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 now
mUnsetPressedState.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 away
setPressed(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 buttons
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
// Remove any future long press/tap checks
removeTapCallback();
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
总结
触摸事件 , 子组件优先进行判定 , 消费触摸事件 ;
如果子组件将事件消费掉 , 则父容器不再进行消费 , 即父容器的触摸事件被屏蔽 ; ( 子组件 )
如果子组件没有讲事件消费掉 , 则在子组件调用返回后 , 在执行父容器的触摸事件 ; ( 先子组件后父容器 )
如果父容器设置了事件拦截 , 此时不会遍历子组件进行事件分发 , 直接调用父容器的触摸事件 ; ( 父容器 )
