事件分发
MotionEvent
- 当用户触摸屏幕时，将产生点击事件，Touch事件的相关细节（发生触摸的位置、时间等）被封装成MotionEvent对象
- 事件列都是以DOWN事件开始、UP事件结束，中间有无数的MOVE事件
- MotionEvent.ACTION_DOWN、MotionEvent.ACTION_UP、MotionEvent.ACTION_MOVE、MotionEvent.ACTION_CANCEL
本质
将点击事件（MotionEvent）传递到某个具体的View & 处理的整个过程
分发顺序
事件传递的顺序：Activity -> ViewGroup -> View
Activity
//1 -------------Activity.java------------
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
//a. 空方法，用于当用户有对屏幕进行操作的回调
onUserInteraction();
}
/** b. getWindow() 返回的是mWindow, mWindow 在Activity attach() 中有初始化mWindow = new PhoneWindow(this, window, activityConfigCallback);
调用2中的方法
**/
if (getWindow().superDispatchTouchEvent(ev)) {
//c. 如果事件有被处理，则直接返回true
return true;
}
//d. 当事件没有被DecorView中任何的View处理或者接收 则会执行onTouchEvent 转4
return onTouchEvent(ev);
}
//2 --------------PhoneWindow.java------------
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
// mDecor 为DecorView DecorView为所有View的根布局，继承自FrameLayout
return mDecor.superDispatchTouchEvent(event);
}
//3 --------------DecorView.java------------
public boolean superDispatchTouchEvent(MotionEvent event) {
/**
1. 调用decorview 的父布局的dispatchTouchEvent()
2. 父布局为FrameLayout，调用的是ViewGroup d的dispatchTouchEvent()
**/
return super.dispatchTouchEvent(event);
}
//4 --------------Activity.java------------
public boolean onTouchEvent(MotionEvent event) {
// 当一个点击事件未被Activity下任何一个View接收 / 处理时
if (mWindow.shouldCloseOnTouch(this, event)) {
finish();
return true;
}
return false;
}
ViewGroup
//1 --------------ViewGroup.java------------
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//1. 初始化局部变量 handled 表示当前事件是否被处理
boolean handled = false;
if (onFilterTouchEventForSecurity(ev)) {
//2. onFilterTouchEventForSecurity 默认返回true 当且仅当设置了当窗口被遮盖时不处理 就会返回false 丢掉所有事件
final int action = ev.getAction();
//3. 获取Action
final int actionMasked = action & MotionEvent.ACTION_MASK;
//4. 获取maskedAction int值的后8位 涉及多点触控
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {
//5. 如果当前事件为ACTION_DOWN时表示当前为全新事件，清除之前保存的状态
// 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.
//6. 定义 intercepted 表示是否被拦截
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//7. 判断当前ViewGourp是否设置过禁止拦截 详情查看requestDisallowInterceptTouchEvent()
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
//8. 如果允许拦截时 调用 onInterceptTouchEvent() 将event恢复为最开始的状态 intercepted的值为方法的返回值
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
//9. 不允许拦截，所以返回的结果时没有被拦截
intercepted = false;
}
} else {
// There are no touch targets and this action is not an initial down
// so this view group continues to intercept touches.
// 10. 当前没有touch targets 并且Action不是ACTION_DOWN 所以intercepted设置为true ？？？
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) {
// 11. 判断事件是否是针对可访问的焦点视图
ev.setTargetAccessibilityFocus(false);
}
// Check for cancelation.
//11. 检查事件是否被取消(ACTION_CANCEL).
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;
// 12.局部变量 newTouchTarget 和 alreadyDispatchedToNewTouchTarget
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
if (!canceled && !intercepted) {
// 13. 如果事件没有取消也没有被拦截 正式进入事件分发
// 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;
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.
//14. 清除此指针ID的早期触摸目标，防止不同步。
removePointersFromTouchTargets(idBitsToAssign);
final int childrenCount = mChildrenCount;//mChildrenCount 是 ViewGroup的成员变量
if (newTouchTarget == null && childrenCount != 0) {
//15. newTouchTarget为之前声明的局部变量
//16. 获取触摸点的坐标
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.
//17. 查找可以接受事件的 ChildView
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
for (int i = childrenCount - 1; i >= 0; i--) {
// 18. 倒序的for循环开始
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(
preorderedList, children, childIndex);
// 如果有一个视图具有可访问性焦点，我们希望它首先获取事件，
// 如果不处理，我们将执行正常的分派。
// 尽管这可能会分发两次，但它能保证在给定的时间内更安全的执行。
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
// 检查View是否允许接受事件(即处于显示状态(VISIBLE)或者正在播放动画)
// 检查触摸位置是否在View区域内
if (!child.canReceivePointerEvents()
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
// getTouchTarget 中判断了 child 是否包含在 mFirstTouchTarget 中
// 如果有返回 target，如果没有返回 null
newTouchTarget = getTouchTarget();
//？？？？？
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;
//已经找到目标View，跳出循环
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);
// 18. 倒序的for循环结束
}
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.
// 没有找到 ChildView 接收事件
newTouchTarget = mFirstTouchTarget;
while (newTouchTarget.next != null) {
newTouchTarget = newTouchTarget.next;
}
newTouchTarget.pointerIdBits |= idBitsToAssign;
}
}
}
// 分发 TouchTarget
if (mFirstTouchTarget == null) {
// 没有 TouchTarget，将当前 ViewGroup 当作普通的 View 处理。
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
// 分发TouchTarget，如果我们已经分发过，则避免分配给新的目标。
// 如有必要，取消分发。
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;
}
}
// 如果需要，更新指针的触摸目标列表或取消
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;
}
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()) {
// 多点触控的情况： 如果子view为null，调用父类View的dispatchEvent()方法,一般情况下后一个判断为false 因为判断了两边child==null 子view不为空的情况在后面
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.
//如果子view为null，调用父类View的dispatchEvent()方法,
if (child == null) {
handled = super.dispatchTouchEvent(transformedEvent);
} else {
//如果子view不为null，调用子view的dispatchTouchEvent()
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;
}
View
- dispatchTouchEvent
//--------------View.java------------
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;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
/** 1. 看条件 li != null&&li.mOnTouchListener != null&& (mViewFlags & ENABLED_MASK) == ENABLED&&li.mOnTouchListener.onTouch(this, event)
li ListenerInfo 是一个静态类, 用于保存设置的各种监听 setXXXListener
如果 li 不为空 并且li 成员变量 mOnTouchListener 不为空 并且 当前view enable 并且 调用mOnTouchListener的onTouch()方法返回true
则 result 为 true
也就是说 如果只要其中一项为false result 就不会被赋值为true 哪些情况
1. 没有设置任何listenser
2. 没有设置onTouchListener
3. 当前view disable
4. 重写的OnTouchListener.onTouch 返回false
**/
if (!result && onTouchEvent(event)) {
result = true;
}
/**
2. 如果result为false 并且 onTouchEvent 返回true result 就赋值为ture
也就是说
1. 当result为true 当前判断就不会进来，onTouchEvent也不会被执行
2. 当result为 false ，onTouchEvent返回false时 result 不会被赋值为true
3. onTouchEvent 方法里进行了事件的判断 click longClick
**/
}
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;
}
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) {
//1. clickable 表示当前view是否可以点击 如果为true 最后返回结果都为ture 转2
switch (action) {
// 若当前的事件为抬起
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) {
// 使用Runnable并发布它，而不是直接调用performClick。这样，在单击操作开始之前，视图的其他视觉状态就会更新。
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
performClickInternal();
//这里调用的就是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(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
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(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
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);
}
final int motionClassification = event.getClassification();
final boolean ambiguousGesture =
motionClassification == MotionEvent.CLASSIFICATION_AMBIGUOUS_GESTURE;
int touchSlop = mTouchSlop;
if (ambiguousGesture && hasPendingLongPressCallback()) {
final float ambiguousMultiplier =
ViewConfiguration.getAmbiguousGestureMultiplier();
if (!pointInView(x, y, touchSlop)) {
// The default action here is to cancel long press. But instead, we
// just extend the timeout here, in case the classification
// stays ambiguous.
removeLongPressCallback();
long delay = (long) (ViewConfiguration.getLongPressTimeout()
* ambiguousMultiplier);
// Subtract the time already spent
delay -= event.getEventTime() - event.getDownTime();
checkForLongClick(
delay,
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
touchSlop *= ambiguousMultiplier;
}
// Be lenient about moving outside of buttons
if (!pointInView(x, y, touchSlop)) {
// Outside button
// Remove any future long press/tap checks
removeTapCallback();
removeLongPressCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
}
final boolean deepPress =
motionClassification == MotionEvent.CLASSIFICATION_DEEP_PRESS;
if (deepPress && hasPendingLongPressCallback()) {
// process the long click action immediately
removeLongPressCallback();
checkForLongClick(
0 /* send immediately */,
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__DEEP_PRESS);
}
break;
}
//2. 如果view clickable为true 返回true
return true;
}
// 如果view clickable为false，就一定返回false
return false;
}
流程
1. Activity
1.1 boolean dispatchTouchEvent()
- 调用DecorView(ViewGroup)的disPatchTouchEvent(),如果事件被消费, 返回true 事件分发结束； 如果没有被消费 则返回下一步onTouchEvent的返回值
1.2 boolean onTouchEvent()
- 默认返回false 除非被重写返回true或者当前页面有设置触摸就关闭
2. ViewGroup
2.1 boolean dispatchTouchEvent()
- 先调用 onInterceptTouchEvent 判断是否拦截
- 如果被拦截，调用super.dispatchTouchEvent() 并将结果返回
- 如果没有被拦截,则遍历了当前ViewGroup下的所有子View，然后调用子View的dispatchTouchEvent 并将返回值返回
2.2 boolean onInterceptTouchEvent()
- 默认返回false表示不拦截 除非有设置或者重写返回true
2.3 boolean onTouchEvent()
- ViewGroup没有重写父类的onTouchEvent
3. View
3.1 boolean dispatchTouchEvent()
- 调用mOnTouchListener的onTouch()方法，如果onTouch()返回true，结束分发
- 如果onTouch()返回false，则调用 onTouchEvent
- 如果onTouchEvent 返回true 则直接返回true
3.2 boolean onTouchEvent()
- 判断是否可点击 clickable 如果为true 则返回ture 否则返回false
- click longClick事件的判断都是在当前方法中判断并执行的
流程总结
图片
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