View中事件分发
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);
}
//是否处理了事件
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
//停止嵌套滑动
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
//如果可见并且在拖动滚动条，则返回true
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
//1.如果设置了OnTouchListener，则调用其onTouch方法，若返回true则dispatchTouchEvent也返回true
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//2.调用onTouchEvent()方法
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;
}
View中的触摸事件要么交给开发者自己处理，要么使用默认处理。
如果开发者想自己来处理触摸事件，可通过setOnTouchListener(OnTouchListener)，在OnTouchListener的onTouch()方法中实现自己的处理逻辑，且onTouch()需要返回true。
默认会调用View的onTouchEvent()方法来进行事件处理：
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
//是否支持点击、长按事件
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.
//如果clickable但是View为disabled，那么也会消费事件只是不响应事件
return clickable;
}
//如果设置了触摸代理则交由其处理事件
if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
//如果可点击或长按，则消费事件
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);
}
//如果没有执行长按事件
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
//从消息队列中移除长按事件消息
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();
}
if (!post(mPerformClick)) {
//执行点击事件
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
//设置可点击标志位
setPressed(true, x, y);
//发送一个延迟消息，用于执行长按事件
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
//如果不在View区域内，则不响应点击、长按事件
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;
}
-
检查是否可点击：View是否设置了点击（setOnClickListener()）或长按事件(setOnLongClickListener())
-
当View为disabled状态时（setEnabled(false)）,若View设置了点击或长按事件，那么View也会消费此次触摸事件，但是不会响应点击或长按事件。
-
如果设置了触摸代理（TouchDelegate）,则交给代理处理触摸事件
-
触发点击事件
在ACTION_DOWN时setPressed(true, x, y);设置点击标志位
在ACTION_MOVE时如果触摸点超出了View区域setPressed(false);将移除点击标志
在ACTION_UP时如果没有执行长按事件，则调用performClick()执行点击事件 -
触发长按事件
在ACTION_DOWN时，checkForLongClick()会通过handle发送一个延迟消息处理长按事件
在ACTION_MOVE时如果触摸点超出了View区域removeLongPressCallback();将移除长按消息
在ACTION_UP时如果还没有执行长按事件将移除长按消息
ViewGroup中事件分发
ViewGroup事件分发分为3个部分：
1.是否拦截触摸事件
2.寻找合适的子View处理触摸事件
3.处理触摸事件
//检查是否拦截事件
final boolean intercepted;
//如果为ACTION_DOWN事件或者已有处理事件的对象
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//是否不允许拦截事件
//子View调用requestDisallowInterceptTouchEvent(true)进行设置
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
//如果允许拦截事件，则调用onInterceptTouchEvent方法决定是否拦截事件
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;
}
子View可通过调用父View的requestDisallowInterceptTouchEvent(true)要求父View不对触摸事件进行拦截，交由子View处理。如果没有子View要求处理触摸事件，则会调用自身onInterceptTouchEvent()方法来决定是否拦截触摸事件，该方法默认不拦截。若拦截事件则自身处理触摸事件，若不拦截则交由子View处理。
//如果非取消事件并且不拦截事件，则在ACTION_DOWN时确定TouchTarget
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;
//如果是ACTION_DOWN事件，找到合适的TouchTarget进行事件处理
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;
//如果newTouchTarget为null
if (newTouchTarget == null && childrenCount != 0) {
//获取触摸位置
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.
//获取排序后的子View列表
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
//遍历所有子View
for (int i = childrenCount - 1; i >= 0; i--) {
//child索引位置
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
//获取子View
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;
}
//如果子View不可见并且没有设置动画并且触摸点没有落在子View上，则继续遍历下一个子View
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
//当子View可见或者设置了动画，并且触摸点位于子View上时
//由于mFirstTouchTarget为null，所以下面代码不会执行
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);
//交由子View处理事件
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 {
//保存最后触摸View的索引
mLastTouchDownIndex = childIndex;
}
//保存最后触摸的位置
mLastTouchDownX = ev.getX();
mLastTouchDownY = ev.getY();
//mFirstTouchTarget为当前处理事件的View
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;
}
}
}
当ViewGroup不拦截事件时，就需要去寻找一个合适的子View来处理触摸事件，只有在触摸事件开始时（ACTION_DOWN）才会去寻找。
遍历ViewGroup的所有子View，当子View可见或者设置了动画，并且触摸点位于子View上时。尝试使用该子View来处理触摸事件，调用其dispatchTouchEvent()方法。
// Dispatch to touch targets.
//开始分发事件
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
//如果没有找到合适的TouchTarget则交由自身处理
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.
//如果有TouchTarget则交由其处理
TouchTarget predecessor = null;
TouchTarget target = mFirstTouchTarget;
while (target != null) {
final TouchTarget next = target.next;
//如果TouchTarget已经处理了（在ACTION_DOWN时）就不再处理
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
//是否TouchTarget取消事件或拦截事件
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
//TouchTarget开始处理事件
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;
}
}
当没有找到合适的子View处理触摸事件或子View没有消费触摸事件时，那么父View会自行处理dispatchTransformedTouchEvent(ev, canceled, null, TouchTarget.ALL_POINTER_IDS)将调用View中的dispatchTouchEvent()方法进行处理。
当找到了合适的子View时,调用dispatchTransformedTouchEvent(ev, cancelChild, target.child, target.pointerIdBits)交给子View处理，该方法又会调用子View的dispatchTouchEvent(),如果子View没有消费触摸事件则又会交由父View进行处理。
一句话概括就是：优先子View处理，如果子View处理不了则自己来处理。
