事件分发操作改变事件状态的主要是在ViewGroup
dispatchTouchEvent
onInterceptTouchEvent
View主要是负责事件的消费
dispatchTouchEvent
onTouchEvent
//ViewGroup dispatchTouchEvent 派发事件方法分析
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
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.
if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
ev.setTargetAccessibilityFocus(false);
}
boolean handled = false;
//验证事件是否是安全事件
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
final int actionMasked = action & MotionEvent.ACTION_MASK;
// Handle an initial down.
//点击事件开始，清除target、touchState等的状态
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);
resetTouchState();
}
// Check for interception.
final boolean intercepted;
//条件解读：1点击事件执行，
//2.获取到的事件view的mFirstTouchTarget=null,会执行else语句-->intercepted = true;
//而没有获取到事件的上级View会存储mFirstTouchTarget，会执行if语句
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;
}
// 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.
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;
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
//获取到事件的view,move事件一定不会执行
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.
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
//down事件执行下面的代码，move事件跳过下面的代码
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
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);
final int childrenCount = mChildrenCount;
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.
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
for (int i = childrenCount - 1; i >= 0; i--) {
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
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. 验证事件的焦点能力
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
//验证事件是否可接受，和点击事件是否在其区域内
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
//返回一个空对象
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.
newTouchTarget.pointerIdBits |= idBitsToAssign;
break;
}
resetCancelNextUpFlag(child);
//将事件派发给子View，递归执行dispatchTouchEvent方法
//子view消费了事件执行下面代码，并初始化mFirstTouchTarget 、newTouchTarget、alreadyDispatchedToNewTouchTarget = true
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
// Child wants to receive touch within its bounds.
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();
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();
}
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.
//down事件：自己再次验证自己是否要处理事件，执行View.dispatchTouchEvent -> onTouchEvent
//move事件：自己消费自己事件
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
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;
while (target != null) {
final TouchTarget next = target.next;
//子view消费了事件，并且是down事件执行
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
//判断是否取消事件传递给子view
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
//派发儿子的move事件，move事件执行
//派发儿子的cancel事件，当上层View拦截了事件：intercepted = true ==> cancelChild = true 执行下面的方法就是执行Child的cancel事件。
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
//当前上层ViewGroup拦截，cancel子View的move事件
//mFirstTouchTarget清空，下次的move事件自己处理。
if (cancelChild) {
if (predecessor == null) {
//中断子View事件传递，将mFirstTouchTarget设为null,下次move事件就给自己派发事件，
//上面的代码if (mFirstTouchTarget == null) {}走这个流程
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;
}
//可见，down事件层层派发并验证，直到有view消费事件
// move事件层层派发不验证，直接派发到消费事件的view
事件派发：ViewGroup 的 dispatchTouchEvent
down move up cancel
1，onFilterTouchEventForSecurity 验证事件的安全性
2，down事件清除之前缓存的时间状态，重置触摸状态
3，判断onInterceptTouchEvent
4，遍历该GroupView的子View，验证接收事件、判断触摸点是否在View内
5，拿到符合的child后执行dispatchTransformedTouchEvent（执行递归child.dispatchTouchEvent）
6，没有符合的child后执行dispatchTransformedTouchEvent参数传递自己执行 View.dispatchTouchEvent(event) 处理事件
7，5有消费的child后递归将child的所有层级的child赋值给其mFirstTouchTarget记录有事件消费了
8，move事件从跟View通过mFirstTouchTarget递归传递到消费Child的父view在传递给消费Child
9, 消费Child的父View获取move事件，消费Child控制getParent().requestDisallowInterceptTouchEvent(false);使得父view可以intercept, 具体操作就是intercept = true,父View将mFirstTouchTarget设置为null，执行自己的派发move事件
整理：down一定要传递到子View，要不子是不可能获取到其事件的，即父View 的 down时间onInterceptTouchEvent不能返回true
/**
* 2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewGroup stackTrace dispatchTransformedTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewGroup stackTrace dispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewGroup stackTrace dispatchTransformedTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewGroup stackTrace dispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: com.android.internal.policy.DecorView stackTrace superDispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: com.android.internal.policy.PhoneWindow stackTrace superDispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.app.Activity stackTrace dispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: androidx.appcompat.view.WindowCallbackWrapper stackTrace dispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: com.android.internal.policy.DecorView stackTrace dispatchTouchEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.View stackTrace dispatchPointerEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$ViewPostImeInputStage stackTrace processPointerEvent
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$ViewPostImeInputStage stackTrace onProcess
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace deliver
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace onDeliverToNext
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace forward
2020-08-06 11:17:56.598 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$AsyncInputStage stackTrace forward
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace apply
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$AsyncInputStage stackTrace apply
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace deliver
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace onDeliverToNext
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace forward
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace apply
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$InputStage stackTrace deliver
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl stackTrace deliverInputEvent
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl stackTrace doProcessInputEvents
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl stackTrace enqueueInputEvent
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.ViewRootImpl$WindowInputEventReceiver stackTrace onInputEvent
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.view.InputEventReceiver stackTrace dispatchInputEvent
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.os.MessageQueue stackTrace nativePollOnce
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.os.MessageQueue stackTrace next
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.os.Looper stackTrace loop
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: android.app.ActivityThread stackTrace main
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: java.lang.reflect.Method stackTrace invoke
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: com.android.internal.os.Zygote$MethodAndArgsCaller stackTrace run
2020-08-06 11:17:56.599 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: com.android.internal.os.ZygoteInit stackTrace main
2020-08-06 11:17:56.600 25184-25184/com.huo.androidbasicstudy V/eventDispatchTest: DispatchTrueEventViewGroup dispatchTouchEvent dispatchTouchEvent
事件传递调用顺序
ViewRootImpl::processPointerEvent
View::dispatchPointerEvent
DecorView::dispatchTouchEvent
WindowCallbackWrapper::dispatchTouchEvent
Activity::dispatchTouchEvent
PhoneWindow::superDispatchTouchEvent
DecorView::superDispatchTouchEvent
ViewGroup::dispatchTouchEvent
ViewGroup::dispatchTransformedTouchEvent
...等等
*/
伴随一次手势，事件分发主要有三种类型的事件，down move up 事件
时间的调用顺序如上面展示的样子。
down事件尽可能的向子view分发，除非有事件拦截onInterceptTouchEvent 返回true，或者dispatchTouchEvent返回true或者false,
- dispatchTouchEvent返回true:由于没有执行父View的dispatchTouchEvent并且自己也没有出里onTouch事件的话，事件会一直传递到该View,并且没有onInterceptTouchEvent和onTouch的事件执行包裹activity的，
- dispatchTouchEvent返回super,交给ViewGroup处理，看onTouch()是否消费事件，没有的话最终由activity消费掉事件。
- dispatchTouchEvent返回false:代表不处理事件，最终事件由activity消费掉。
activity消费掉事件的原理 : 所有的View或者ViewGroup都没有处理down事件在onTouch()中，或者说onTouch()返回false。在分发move或者up事件的时候,在事件分发到DecorView，调用superDispatchTouchEvent()执行ViewGroup的dispatchTouchEvent()就返回了false(mFirstTouchTarget == null)，在DecorView就结束了事件传递，并由activity来消费事件,这也是在没有处理down事件的时候也接收不到move和up事件的原因。 - onInterceptTouchEvent 返回true，dispatchTouchEvent中拦截事件，交给自己的onTouch()处理
- onInterceptTouchEvent 返回false, 不拦截事件，事件继续派发dispatchTouchEvent()。
- onInterceptTouchEvent 返回super,交给父类处理拦截事件。
- onInterceptTouchEvent 方法执行条件，（down事件 or mFirstTouchTarget != null ) & !disallowIntercept
- onTouch() 返回true,消费事件，后续事件都传递到这里。
- onTouch() 返回false,不消费事件，事件向外层View传递。
- onTouch() 返回super,交给父类判断是否要消费。
down事件设置mFirstTouchTarget
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