事件传递
当一个点击事件发生时，事件最先传递给当前Activity，由Activity 的 dispatchTouchEvent 来进行事件分发，具体的工作是由Activity 内部的Window 来完成(即PhoneWindow)，Window 会将事件传递给 decor view， decor view 一般就是当前的底层容器（即setContent 所设置的 View 的父容器），通过 Activity.getWindow.getDecorView() 获取，通过ViewGroup 的事件分发，传递到最终的View 上
Activity 的
dispatchTouchEvent
/**
* 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) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {//事件开始交给Activity 所附属的 Window 进行分发
return true;
}
return onTouchEvent(ev);
}
首先事件开始交给Activity 所附属的 Window 进行分发，如果返回 true ，整个事件循环就结束了，返回false 意味着事件没人处理，所有 View 的onTouchEvent 都返回了 false，则 Activity 的 onTouchEvent 就会被调用
由于Window 是抽象类，且Window 的 superDispatchTouchEvent 方法也是抽象方法，故需找到Window 的唯一实现类 PhoneWindow
PhoneWindow 源码：
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
return mDecor.superDispatchTouchEvent(event);
}
DecorView
public class DecorView extends FrameLayout implements RootViewSurfaceTaker, WindowCallbacks {
// This is the top-level view of the window, containing the window decor.
private DecorView mDecor;
@Override
public final View getDecorView() {
if (mDecor == null || mForceDecorInstall) {
installDecor();
}
return mDecor;
}
这个DecorView 就是我们视图的根View，它里面有两个子View，一个TitleView，一个ContentView，这个ContentView 就是我们在Activity 中通过 setContentView 所设置的 View，由于 DecorView 继承自 FrameLayout ，且是父View，所以事件最终会传递给View。
顶级View 对点击事件的分发过程
点击事件到达顶级View 之后，会调用ViewGroup 的 dispatchTouchEvent 方法，然后的逻辑如下：如果顶级ViewGroup 拦截事件即 onInterceptTouchEvent 返回 true，则事件由 ViewGroup 处理，此时如果 ViewGroup 的 mOnTouchListener 被设置，则 onTouch 会被调用，否则 onTouchEvent 会被调用，即如果给控件设置了 onTouchListener 监听，则onTouch 会屏蔽掉 onTouchEvent 。在 onTouchEvent 中，如果设置了 mOnClickListener ，则onClick 会被调用。
即 onTouchListener 的优先级大于 onTouchEvent 大于 onClick
如果顶级ViewGroup 不拦截事件，则事件会传递给它所在的点击事件链上的子 View，这时子 View 的 dispatchTouchEvent 会被调用，此时事件已经从顶级View 传递给了下一层View ，接下来的传递过程和顶级 View 是一致的，如此循环，完成整个事件的分发
@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;
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
final int actionMasked = action & MotionEvent.ACTION_MASK;
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {//重置标记位
// 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;//检查是否拦截事件的标志位
//通过 DOWN 事件和 mFirstTouchTarget 是否为空 判断是否拦截当前事件，mFirstTouchTarget在ViewGroup 的子View 成功消费事件时赋值，
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
//通过disallowIntercept 来判断是否拦截当前事件，其可通过requestDisallowInterceptTouchEvent 来设置，默认为 false
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;
if (!canceled && !intercepted) {
// If the event is targeting accessiiblity 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;
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.
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
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);
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.
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;
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
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;
}
final boolean intercepted;//检查是否拦截事件的标志位
//通过 DOWN 事件和 mFirstTouchTarget 是否为空 判断是否拦截当前事件，mFirstTouchTarget在ViewGroup 的子View 成功消费事件时赋值，
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
//通过disallowIntercept 来判断是否拦截当前事件，其可通过requestDisallowInterceptTouchEvent 来设置，默认为 false
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;
}
从上可知，ViewGroup 在两种情况下会判断是否拦截当前事件：
事件类型为 DOWN 或者
mFirstTouchTarget != null，
当事件被顶级View 的子 View 消费时，
mFirstTouchTarget 会被赋值并指向子 View；
如果事件被拦截，则
mFirstTouchTarget != null 就不会成立，当ACTION_MOVE、ACTION_UP 到来时，判断条件不成立，导致ViewGroup 的 onInterceptTouchEvent(ev)方法就不会被调用， intercepted = true; 并且同一序列（即从down-move-move...up 的一系列事件）中的其他事件都会默认交给这个View 处理
FLAG_DISALLOW_INTERCEPT 标记位：可通过 requestDisallowInterceptTouchEvent 方法来设置，一般用于子View 中，其默认值为 false；由上述代码可以看出，当该标记位为 true 时，ViewGroup 的 onInterceptTouchEvent(ev)方法就不会被调用，intercepted = false;ViewGroup 将无法拦截除了 ACTION_DOWN 事件外的其它事件，其原因如下源码所示：
// Handle an initial down.
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();//重置FLAG_DISALLOW_INTERCEPT
}
从源码中可知，当ViewGroup 在分发事件时，如果是ACTION_DOWN 事件，则会重置 FLAG_DISALLOW_INTERCEPT 标记位，导致子View 中设置的这个标记位无效，即每一个ACTION_DOWN 都会先重置标记位，在View 的ACTION_DOWN 事件中调用requestDisallowInterceptTouchEvent 毫无意义
FLAG_DISALLOW_INTERCEPT 一旦设置后，ViewGroup 将无法拦截除了 ACTION_DOWN 事件外的其他点击事件，当面对 ACTION_DOWN 事件时， ViewGroup 总会调用自己的 onInterceptTouchEvent 方法询问自己是否要拦截事件，在ViewGroup 中会在ACTION_DOWN 事件到来时做重置状态的操作，在resetTouchState 方法中会对 FLAG_DISALLOW_INTERCEPT 进行重置，所以 View 调用
requestDisallowInterceptTouchEvent 方法并不能影响 ViewGroup 对 ACTION_DOWN 事件的处理
ViewGroup 的事件分发源码
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.
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
//判断子元素是否在播放动画和点击事件是否落在子元素区域
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
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);
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {//根据是否有子View 来分发事件
// 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;
}
dispatchTransformedTouchEvent 源码
/**
* 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;
}
如果子元素的 dispatchTouchEvent 返回 true，则mFirstTouchTarget 会被赋值并跳出循环。
addTouchTarget(child, idBitsToAssign)源码
/**
* 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;
}
这里完成了mFirstTouchTarget 的赋值并终止了对子元素的便利，如果子元素的 dispatchTouchEvent 返回false，则ViewGroup 会把事件分发给下一个子元素，直到遍历完所有的子元素
如果mFirstTouchTarget 为null ，即ViewGroup 没有子元素或者子元素在 onTouchEvent 中返回了 false，此时就会调用下面的代码
// 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);
}
注意这里第三个参数chile 为 null，从前面的dispatchTransformedTouchEvent 中可知，他会调用super.dispatchTouchEvent(event);方法，这里就转到了View 的 dispatchTouchEvent 方法，即点击事件开始交由View 来处理
onInterceptTouchEvent 方法
public boolean onInterceptTouchEvent(MotionEvent ev) {
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;
}从源码中可看出，
onInterceptTouchEvent 默认返回 false，即ViewGroup 默认不拦截认可事件
View 的 diapatchTouchEvent 方法源码：
public boolean dispatchTouchEvent(MotionEvent event) {
// 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);
}
boolean result = false;
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
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
ListenerInfo li = mListenerInfo;
//判断是否设置 onTouchListener 监听
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
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;
}
从上述源码中可看出，如果View 设置了 onTouchListener ，则它的 onTouch方法会调用，如果onTouch 方法返回 true，则onTouchEvent 方法就不会被调用，可见OnTouchListener 的优先级高于 onTouchEvent
onTouchEvent
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;
//View 处于不可点击状态下的点击事件的处理过程
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;//返回clickable
}
if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
//只要View 的 CLICKABLE 和LONG_CLICKABLE 有一个为true，就会消耗这个事件，即onTouchEvent 返回 true
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_UP:
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) {
mPerformClick = new PerformClick();//点击事件消费的地方
}
if (!post(mPerformClick)) {
performClick();
}
}
}
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;//onTouchEvent 返回 true
}
return false;
}
当 ACTION_UP 事件发生时，会触发 performClick 方法，如果View 设置了 OnClickListener ，则performClick 会内部调用它的 onClick 方法
performClick 源码：
public boolean performClick() {
final boolean result;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
li.mOnClickListener.onClick(this);
result = true;
} else {
result = false;
}
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
notifyEnterOrExitForAutoFillIfNeeded(true);
return result;
}
由上可知，如果 View 设置了 OnClickListener，则performClick 方法内部会调用它的 onClick 方法
View 的LONG_CLICKABLE 属性默认为false，而CLICKABLE 属性是否为 false和具体的View 有关，具体说就是可点击的View 的CLICKABLE 为true ，不可点击的View CLICKABLE 为false，可通过setOnLongClickListener 和 改变View 的LONG_CLICKABLE 和 CLICKABLE 属性，会分别将LONG_CLICKABLE 和 CLICKABLE 自动置为 trues
public void setOnClickListener(@Nullable OnClickListener l) {
if (!isClickable()) {
setClickable(true);
}
getListenerInfo().mOnClickListener = l;
}
setOnLongClickListener
public void setOnLongClickListener(@Nullable OnLongClickListener l) {
if (!isLongClickable()) {
setLongClickable(true);
}
getListenerInfo().mOnLongClickListener = l;
}
结论：
- 同一个事件序列是指从手指接触屏幕的那一刻起，直到手指离开屏幕的那一刻结束所产生的一系列事件。这个事件序列以 down事件开始，中间包含一系列 move 事件，最终以 up 事件结束
- 正常情况下，一个事件序列只能被一个View 拦截且消费
- 某个 View 一旦决定拦截事件，则这一个事件序列都会交由它来处理，且它的 onInterceptTouchEvent 不会再被调用，从ViewGroup 源码事件的拦截判断中可得出
- 某个View 一旦开始处理事件，如果它不消耗 ACTION_DOWN 事件(即 onTouchEvent 返回了 false)，则统一事件序列的其他事件都不会再交给他来处理，并且事件将重新交由它的父元素去处理，即父元素的 onTouchEvent 会被调用，从ViewGroup 源码事件的拦截判断中可得出
-
ViewGroup 默认不拦截任何事件，Android 源码中 ViewGroup 的 onInterceptTouchEvent 方法默认返回 false
-
View 没有 onInterceptTouchEvent 方法，一旦有点击事件传递给它，则它的 onTouchEvent 方法就会被调用
-
View 的 onTouchEvent 方法默认返回 true ，除非他是不可点击的
-
View 的 enable 属性不影响 onTouchEvent 的默认返回值。哪怕一个View 是 disable 状态，只要他的 clickable 或者 longClickable 有一个为 true，则它的onTouchEvent 就返回 true
-
onClick 会发生的前提是当前View 可点击，且收到了 down 和 up 事件
-
事件的传递是由外向内的，即事件总是先传递到父元素，然后由父元素分发给子 View，通过调用 requestDisableIntercepTouchEvent 可在子元素中干预父元素的事件分发过程，但 ACTION_DOWN事件除外