了解更多,移步Android触摸事件传递机制系列详解
Android触摸事件的传递(六)-ViewRootImpl-->Activity
1 activity的dispatchTouchEvent方法
activity
和Dialog
都是Callback
接口的具体实现,主要看activity
的dispatchTouchEvent
方法,
public boolean dispatchTouchEvent(MotionEvent ev) {
•••
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
首先调用PhoneWindow
的superDispatchTouchEvent
方法,如果未处理才继续调用onTouchEvent
方法
2 DecorView的superDispatchTouchEvent
Window
的superDispatchTouchEvent
是个抽象方法
public abstract boolean superDispatchTouchEvent(MotionEvent event);
找到window
的实现类---PhoneWindow
(wingdow的唯一实现)
public boolean superDispatchTouchEvent(MotionEvent event){
return mDecor.superDispatchTouchEvent(event);
};
直接调用DecorView的superDispatchTouchEvent
3 ViewGoup--dispatchTouchEvent
-
DecorView
继承自FrameLayout
且是父view,所以事件最终传递给了ViewGroup
-
DecorView
一般就是当前底层容器(即setContentView
所设置的View
的父容器) - 通过
Activity.getWindow().getDecorView();
获得
通过下面可以获得activity
所设置的view
,setContentView
设置的view
是其一个子view
。
((ViewGroup)getWindow().getDecorView().findViewById(android.R.id.content)).getChildAt(0);
public boolean dispatchTouchEvent(MotionEvent ev) {
//验证事件是否连续
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
}
//这个变量用于记录事件是否被处理完
boolean handled = false;
//过滤掉一些不合法的事件:当前的View的窗口被遮挡了。
if (onFilterTouchEventForSecurity(ev)) {
//如果事件发生的View在的窗口,没有被遮挡
final int action = ev.getAction();
//重置前面为0 ,只留下后八位,用于判断相等时候,可以提高性能。
final int actionMasked = action & MotionEvent.ACTION_MASK;
//判断是不是Down事件,如果是的话,就要做初始化操作
if (actionMasked == MotionEvent.ACTION_DOWN) {
//如果是down事件,就要清空掉之前的状态,比如,重置手势判断什么的。
//比如,之前正在判断是不是一个单点的滑动,但是第二个down来了,就表示,不可能是单点的滑动,要重新开始判断触摸的手势
//清空掉mFirstTouchTarget
// 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);
resetTouchState();
}
//检查是否拦截事件
final boolean intercepted;
//如果当前是Down事件,或者已经有处理Touch事件的目标了
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//判断允不允许这个View拦截
//使用与运算作为判断,可以让我们在flag中,存储好几个标志
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
//如果说允许拦截事件
if (!disallowIntercept) {
//确定是不是拦截了
intercepted = onInterceptTouchEvent(ev);
//重新恢复Action,以免action在上面的步骤被人为地改变了
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.
//如果说,事件已经初始化过了,并且没有子View被分配处理,那么就说明,这个ViewGroup已经拦截了这个事件
intercepted = true;
}
// Check for cancelation.
//如果viewFlag被设置了PFLAG_CANCEL_NEXT_UP_EVENT ,那么就表示,下一步应该是Cancel事件
//或者如果当前的Action为取消,那么当前事件应该就是取消了。
final boolean canceled = resetCancelNextUpFlag(this)
|| actionMasked == MotionEvent.ACTION_CANCEL;
// Update list of touch targets for pointer down, if needed.
//如果需要(不是取消,也没有被拦截)的话,那么在触摸down事件的时候更新触摸目标列表
//split代表,当前的ViewGroup是不是支持分割MotionEvent到不同的View当中
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
//新的触摸对象,
TouchTarget newTouchTarget = null;
//是否把事件分配给了新的触摸
boolean alreadyDispatchedToNewTouchTarget = false;
//事件不是取消事件,也没有拦截那么就要判断
if (!canceled && !intercepted) {
//如果是个全新的Down事件
//或者是有新的触摸点
//或者是光标来回移动事件(不太明白什么时候发生)
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
//这个事件的索引,也就是第几个事件,如果是down事件就是0
final int actionIndex = ev.getActionIndex(); // always 0 for down
//获取分配的ID的bit数量
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.
//清理之前触摸这个指针标识,以防他们的目标变得不同步。
removePointersFromTouchTargets(idBitsToAssign);
final int childrenCount = mChildrenCount;
//如果新的触摸对象为null(这个不是铁定的吗)并且当前ViewGroup有子元素
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.
//下面所做的工作,就是找到可以接收这个事件的子元素
final View[] children = mChildren;
//是否使用自定义的顺序来添加控件
final boolean customOrder = isChildrenDrawingOrderEnabled();
for (int i = childrenCount - 1; i >= 0; i--) {
//如果是用了自定义的顺序来添加控件,那么绘制的View的顺序和mChildren的顺序是不一样的
//所以要根据getChildDrawingOrder取出真正的绘制的View
//自定义的绘制,可能第一个会画到第三个,和第四个,第二个画到第一个,这样里面的内容和Children是不一样的
final int childIndex = customOrder ?
getChildDrawingOrder(childrenCount, i) : i;
final View child = children[childIndex];
//如果child不可以接收这个触摸的事件,或者触摸事件发生的位置不在这个View的范围内
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
continue;
}
//获取新的触摸对象,如果当前的子View在之前的触摸目标的列表当中就返回touchTarget
//子View不在之前的触摸目标列表那么就返回null
newTouchTarget = getTouchTarget(child);
if (newTouchTarget != null) {
// Child is already receiving touch within its bounds.
// Give it the new pointer in addition to the ones it is handling.
//如果新的触摸目标对象不为空,那么就把这个触摸的ID赋予它,这样子,
//这个触摸的目标对象的id就含有了好几个pointer的ID了
newTouchTarget.pointerIdBits |= idBitsToAssign;
break;
}
//如果子View不在之前的触摸目标列表中,先重置childView的标志,去除掉CACEL的标志
resetCancelNextUpFlag(child);
//调用子View的dispatchTouchEvent,并且把pointer的id 赋予进去
//如果说,子View接收并且处理了这个事件,那么就更新上一次触摸事件的信息,
//并且为创建一个新的触摸目标对象,并且绑定这个子View和Pointer的ID
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
// Child wants to receive touch within its bounds.
mLastTouchDownTime = ev.getDownTime();
mLastTouchDownIndex = childIndex;
mLastTouchDownX = ev.getX();
mLastTouchDownY = ev.getY();
//这里给mFirstTouchTarget赋值
newTouchTarget = addTouchTarget(child, idBitsToAssign);
alreadyDispatchedToNewTouchTarget = true;
break;
}
}
}
//如果newTouchTarget为null,就代表,这个事件没有找到子View去处理它,
//那么,如果之前已经有了触摸对象(比如,我点了一张图,另一个手指在外面图的外面点下去)
//那么就把这个之前那个触摸目标定为第一个触摸对象,并且把这个触摸(pointer)分配给最近添加的触摸目标
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;
}
}
}
// Dispatch to touch targets.
//如果没有触摸目标
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
//那么就表示我们要自己在这个ViewGroup处理这个触摸事件了
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
// 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;
//遍历TouchTargt树.分发事件,如果我们已经分发给了新的TouchTarget那么我们就不再分发给newTouchTarget
while (target != null) {
final TouchTarget next = target.next;
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
//是否让child取消处理事件,如果为true,就会分发给child一个ACTION_CANCEL事件
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
//派发事件
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
//cancelChild也就是说,派发给了当前child一个ACTION_CANCEL事件,
//那么就移除这个child
if (cancelChild) {
//没有父节点,也就是当前是第一个TouchTarget
//那么就把头去掉
if (predecessor == null) {
mFirstTouchTarget = next;
} else {
//把下一个赋予父节点的上一个,这样当前节点就被丢弃了
predecessor.next = next;
}
//回收内存
target.recycle();
//把下一个赋予现在
target = next;
//下面的两行不执行了,因为我们已经做了链表的操作了。
//主要是我们不能执行predecessor=target,因为删除本节点的话,父节点还是父节点
continue;
}
}
//如果没有删除本节点,那么下一轮父节点就是当前节点,下一个节点也是下一轮的当前节点
predecessor = target;
target = next;
}
}
// Update list of touch targets for pointer up or cancel, if needed.
//遇到了取消事件、或者是单点触摸下情况下手指离开,我们就要更新触摸的状态
if (canceled
|| actionMasked == MotionEvent.ACTION_UP
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
resetTouchState();
} else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {
//如果是多点触摸下的手指抬起事件,就要根据idBit从TouchTarget中移除掉对应的Pointer(触摸点)
final int actionIndex = ev.getActionIndex();
final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);
removePointersFromTouchTargets(idBitsToRemove);
}
}
if (!handled && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);
}
return handled;
}
3.1 解析一:检查是否拦截事件
-
viewgroup
会在两种情况下会判断是否要拦截当前事件:事件类型为ACTION_DOWN
或者mFirstTouchTarget != null
。 - 当事件交由
viewgroup
的子元素处理时,mFirstTouchTarge
t被赋值并指向子元素,事件传递给子元素时才不为null。
通常
-
ACTION_DOWN
的时候mFirstTouchTarget
还是null
。 -
ACTION_DOWN
后面的事件mFirstTouchTarget
不为null
。 -
ACTION_DOWN
后面的事件mFirstTouchTarget
为null
了viewgroup
默认拦截 。 - onInterceptTouchEvent默认返回false,viewgroup`默认不拦截
//检查是否拦截事件
final boolean intercepted;
//如果当前是Down事件,或者已经有处理Touch事件的目标了
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//判断允不允许这个View拦截
//使用与运算作为判断,可以让我们在flag中,存储好几个标志
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
//如果说允许拦截事件
if (!disallowIntercept) {
//确定是不是拦截了
intercepted = onInterceptTouchEvent(ev);
//重新恢复Action,以免action在上面的步骤被人为地改变了
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.
//如果说,事件已经初始化过了,并且没有子View被分配处理,那么就说明,这个ViewGroup已经拦截了这个事件
intercepted = true;
}
onInterceptTouchEvent默认返回false
public boolean onInterceptTouchEvent(MotionEvent ev) {
return false;
}
3.2 检查子view并传递事件
- 判断事件不是取消事件,也没有拦截
if (!canceled && !intercepted) {***}
- 判断child可不可以接收这个触摸的事件,或者触摸事件发生的位置在不在这个View的范围内
- 条件通过该子view 则赋值给newTouchTarget
- dispatchTransformedTouchEvent调用子View的dispatchTouchEvent,并且把pointer的id 赋予进去.如果说,子View接收并且处理了这个事件。如果返回true,则
alreadyDispatchedToNewTouchTarget = true;//已经消费事件
并跳出循环。否则继续遍历循环。
//事件不是取消事件,也没有拦截那么就要判断
if (!canceled && !intercepted) {
//如果是个全新的Down事件
//或者是有新的触摸点
//或者是光标来回移动事件(不太明白什么时候发生)
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
//这个事件的索引,也就是第几个事件,如果是down事件就是0
final int actionIndex = ev.getActionIndex(); // always 0 for down
//获取分配的ID的bit数量
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.
//清理之前触摸这个指针标识,以防他们的目标变得不同步。
removePointersFromTouchTargets(idBitsToAssign);
final int childrenCount = mChildrenCount;
//如果新的触摸对象为null(这个不是铁定的吗)并且当前ViewGroup有子元素
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.
//下面所做的工作,就是找到可以接收这个事件的子元素
final View[] children = mChildren;
//是否使用自定义的顺序来添加控件
final boolean customOrder = isChildrenDrawingOrderEnabled();
for (int i = childrenCount - 1; i >= 0; i--) {
//如果是用了自定义的顺序来添加控件,那么绘制的View的顺序和mChildren的顺序是不一样的
//所以要根据getChildDrawingOrder取出真正的绘制的View
//自定义的绘制,可能第一个会画到第三个,和第四个,第二个画到第一个,这样里面的内容和Children是不一样的
final int childIndex = customOrder ?
getChildDrawingOrder(childrenCount, i) : i;
final View child = children[childIndex];
//如果child不可以接收这个触摸的事件,或者触摸事件发生的位置不在这个View的范围内
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
continue;
}
//获取新的触摸对象,如果当前的子View在之前的触摸目标的列表当中就返回touchTarget
//子View不在之前的触摸目标列表那么就返回null
newTouchTarget = getTouchTarget(child);
if (newTouchTarget != null) {
// Child is already receiving touch within its bounds.
// Give it the new pointer in addition to the ones it is handling.
//如果新的触摸目标对象不为空,那么就把这个触摸的ID赋予它,这样子,
//这个触摸的目标对象的id就含有了好几个pointer的ID了
newTouchTarget.pointerIdBits |= idBitsToAssign;
break;
}
//如果子View不在之前的触摸目标列表中,先重置childView的标志,去除掉CACEL的标志
resetCancelNextUpFlag(child);
//调用子View的dispatchTouchEvent,并且把pointer的id 赋予进去
//如果说,子View接收并且处理了这个事件,那么就更新上一次触摸事件的信息,
//并且为创建一个新的触摸目标对象,并且绑定这个子View和Pointer的ID
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
// Child wants to receive touch within its bounds.
mLastTouchDownTime = ev.getDownTime();
mLastTouchDownIndex = childIndex;
mLastTouchDownX = ev.getX();
mLastTouchDownY = ev.getY();
//这里给mFirstTouchTarget赋值
newTouchTarget = addTouchTarget(child, idBitsToAssign);
alreadyDispatchedToNewTouchTarget = true;
break;
}
}
}
//如果newTouchTarget为null,就代表,这个事件没有找到子View去处理它,
//那么,如果之前已经有了触摸对象(比如,我点了一张图,另一个手指在外面图的外面点下去)
//那么就把这个之前那个触摸目标定为第一个触摸对象,并且把这个触摸(pointer)分配给最近添加的触摸目标
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;
}
}
}
3.3 自己处理事件
- 如果没有触摸目标那么就表示我们要自己在这个ViewGroup处理这个触摸事件了
handled = dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);
- 注:如果检查子view没有消费掉事件
- 如果有 则遍历TouchTargt树分发事件,如果我们已经分发给了新的TouchTarget那么我们就不再分发给newTouchTarget
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {handled = true;}
否则是否让child取消处理事件,如果为true,就会分发给child一个ACTION_CANCEL事件
// Dispatch to touch targets.
//如果没有触摸目标
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
//那么就表示我们要自己在这个ViewGroup处理这个触摸事件了
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
// 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;
//遍历TouchTargt树.分发事件,如果我们已经分发给了新的TouchTarget那么我们就不再分发给newTouchTarget
while (target != null) {
final TouchTarget next = target.next;
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
//是否让child取消处理事件,如果为true,就会分发给child一个ACTION_CANCEL事件
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
//派发事件
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
//cancelChild也就是说,派发给了当前child一个ACTION_CANCEL事件,
//那么就移除这个child
if (cancelChild) {
//没有父节点,也就是当前是第一个TouchTarget
//那么就把头去掉
if (predecessor == null) {
mFirstTouchTarget = next;
} else {
//把下一个赋予父节点的上一个,这样当前节点就被丢弃了
predecessor.next = next;
}
//回收内存
target.recycle();
//把下一个赋予现在
target = next;
//下面的两行不执行了,因为我们已经做了链表的操作了。
//主要是我们不能执行predecessor=target,因为删除本节点的话,父节点还是父节点
continue;
}
}
//如果没有删除本节点,那么下一轮父节点就是当前节点,下一个节点也是下一轮的当前节点
predecessor = target;
target = next;
}
}
3.4 dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,View child, int desiredPointerIdBits)
- 通过以上代码可知
- 对于目标子view调用如
dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)
- ViewGroup自己处理事件调用
dispatchTransformedTouchEvent(ev, canceled, null,TouchTarget.ALL_POINTER_IDS);
- 当让child取消处理事件,如果为true,就会分发给child一个ACTION_CANCEL事件。调用
dispatchTransformedTouchEvent(ev, cancelChild,target.child, target.pointerIdBits)
可以看出 在ViewGroup自己处理时child为null。其他child不为null。
dispatchTransformedTouchEvent
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) {
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;
}
- 通过查看
dispatchTransformedTouchEvent
可以看出当child
为null
时调用super.dispatchTouchEvent(event);
而child
不为null
时调用child.dispatchTouchEvent(event)
- 由此可以看出ViewGroup或子view自身真正处理事件时都是通过View的dispatchTouchEvent分发下去的。
参考
View的事件分发机制——dispatchTouchEvent详解