Android知识总结
一、在ViewGroup 事件分发
ViewGroup#dispatchTouchEvent 分发事件
public boolean dispatchTouchEvent(MotionEvent ev) {
//验证事件是否连续
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
}
// 残障人事的辅助类，智能聊天
if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
ev.setTargetAccessibilityFocus(false);
}
//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)) {
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;
// Handle an initial down.
// 多指还单指，只会执行一次 -- Action_point_donw
// 重置状态
if (actionMasked == MotionEvent.ACTION_DOWN) {
cancelAndClearTouchTargets(ev);
resetTouchState();
}
/***********************************第一块, 检测是否拦截*******************************/
// Check for interception.
// 检测是否拦截 -- 父容器的权利
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//判断允不允许这个View拦截，在内部拦截中子View请求 requestDisallowInterceptTouchEvent
//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;
// disallowIntercept 决定 onInterceptTouchEvent 会不会执行
if (!disallowIntercept) {
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.
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);
}
//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.
final boolean isMouseEvent = ev.getSource() == InputDevice.SOURCE_MOUSE;
// 默认情况为true -- 是否可以多指
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0
&& !isMouseEvent;
//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;
/************************第二块, 遍历子View，询问子View是否处理事件*******************/
// 在 if 中分发事件
if (!canceled && !intercepted) {
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
// 第一根手指按下时，命中if
if (actionMasked == MotionEvent.ACTION_DOWN
// 第二根或n根手指按下，命中if
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
// 鼠标
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
// 如果事件是 MotionEvent.ACTION_DOWN，actionIndex = 0
final int actionIndex = ev.getActionIndex(); // always 0 for down
// 手指的id ，最多识别多少手指？32位，位运算，一位表示一个手指，0000000000111
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);
// 有多少个子孩子
final int childrenCount = mChildrenCount;
if (newTouchTarget == null && childrenCount != 0) {
final float x =
isMouseEvent ? ev.getXCursorPosition() : ev.getX(actionIndex);
final float y =
isMouseEvent ? ev.getYCursorPosition() : ev.getY(actionIndex);
// Find a child that can receive the event.
// Scan children from front to back.
// 将子View 进行排序
final ArrayList preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
// 倒序遍历
for (int i = childrenCount - 1; i >= 0; i--) {
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(
preorderedList, children, childIndex);
// 是否能处理点击事件
// view是否可见或者animotion不为空
if (!child.canReceivePointerEvents()
|| !isTransformedTouchPointInView(x, y, child, null)) {
continue;
}
// 单指操作，为null，多指才不为空
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;
}
//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);
// 询问 child 是否处理事件，如果child处理，则命中if -- 递归
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();
// 创建了 newTouchTarget == mFirstTouchTarget
newTouchTarget = addTouchTarget(child, idBitsToAssign);
// 后面会子View处理事件用到
alreadyDispatchedToNewTouchTarget = true;
// 退出循环，不再循环其他child
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();
}
//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;
}
}
}
/************************第三块, 判断子View处理还是自己处理事件*******************/
// Dispatch to touch targets.
// 没有child处理事件的时候
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
// 询问自己是否处理
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
// 有子View处理了事件
TouchTarget predecessor = null;
TouchTarget target = mFirstTouchTarget;
// while循环为单指操作时 只会执行一次
while (target != null) {
// 单指操作 next = null
final TouchTarget next = target.next;
// if命中，直接返回 handle，不作处理。（根据局部变量 alreadyDispatchedToNewTouchTarget
//确认只有Action_Down才能命中
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else { //其他Action 执行，如：Action_Move
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
// 询问 target.child（前面保存的之View）
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
// 为true 取消child处理事件
if (cancelChild) {
if (predecessor == null) {
// mFirstTouchTarget 置为null
mFirstTouchTarget = next;
} else {
predecessor.next = next;
}
//回收内存
target.recycle();
//把下一个赋予现在
target = next;
continue;
}
}
predecessor = target;
target = next;
}
}
// 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;
}
//参数 disallowIntercept 为 true 让parent 不拦截
//参数 disallowIntercept 为 fslse 让parent 拦截
@Override
public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) {
// We're already in this state, assume our ancestors are too
return;
}
if (disallowIntercept) {
mGroupFlags |= FLAG_DISALLOW_INTERCEPT;
} else {
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
}
// Pass it up to our parent
if (mParent != null) {
mParent.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}
可见ViewGroup#dispatchTouchEvent分为三部分
- 1、是否拦截子View,intercepted为true拦截，为false 不拦截
- 2、遍历子View，询问子View是否处理事件
- 3、如果子View都不处理，询问自己是否处理事件
1.1、 取消事件和重置状态
- 执行取消事件
private void cancelAndClearTouchTargets(MotionEvent event) {
if (mFirstTouchTarget != null) {
boolean syntheticEvent = false;
if (event == null) {
final long now = SystemClock.uptimeMillis();
event = MotionEvent.obtain(now, now,
MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0);
event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
syntheticEvent = true;
}
for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) {
resetCancelNextUpFlag(target.child);
// 执行取消事件
dispatchTransformedTouchEvent(event, true, target.child, target.pointerIdBits);
}
// 清除 TouchTarget
clearTouchTargets();
if (syntheticEvent) {
event.recycle();
}
}
}
- 重置状态
private void resetTouchState() {
clearTouchTargets();
resetCancelNextUpFlag(this);
// 重置了 mGroupFlags 的值
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
mNestedScrollAxes = SCROLL_AXIS_NONE;
}
1.2、拦截事件
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;
}
我们在自定义View 里面可以重写这个方法来处理拦截事件
1.3、询问子View是否处理事件
在里面会对子View 根据悬浮层进行排序
public ArrayList buildTouchDispatchChildList() {
return buildOrderedChildList();
}
ArrayList buildOrderedChildList() {
final int childrenCount = mChildrenCount;
if (childrenCount <= 1 || !hasChildWithZ()) return null;
if (mPreSortedChildren == null) {
mPreSortedChildren = new ArrayList<>(childrenCount);
} else {
// callers should clear, so clear shouldn't be necessary, but for safety...
mPreSortedChildren.clear();
mPreSortedChildren.ensureCapacity(childrenCount);
}
final boolean customOrder = isChildrenDrawingOrderEnabled();
for (int i = 0; i < childrenCount; i++) {
// add next child (in child order) to end of list
final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
final View nextChild = mChildren[childIndex];
// 默认不设置，则为0
final float currentZ = nextChild.getZ();
// insert ahead of any Views with greater Z
int insertIndex = i;
while (insertIndex > 0 && mPreSortedChildren.get(insertIndex - 1).getZ() > currentZ) {
insertIndex--;
}
// xml中布局 靠后的，放在集合后面
mPreSortedChildren.add(insertIndex, nextChild);
}
return mPreSortedChildren;
}
private int getAndVerifyPreorderedIndex(int childrenCount, int i, boolean customOrder) {
final int childIndex;
if (customOrder) {
final int childIndex1 = getChildDrawingOrder(childrenCount, i);
if (childIndex1 >= childrenCount) {
throw new IndexOutOfBoundsException("getChildDrawingOrder() "
+ "returned invalid index " + childIndex1
+ " (child count is " + childrenCount + ")");
}
childIndex = childIndex1;
} else {
childIndex = i;
}
return childIndex;
}
1.4、询问子View处理，还是自己处理
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();
//当取消事件会执行这里，内部拦截也会走
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
//把事件先设为 ACTION_CANCEL
event.setAction(MotionEvent.ACTION_CANCEL);
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
handled = child.dispatchTouchEvent(event);
}
//设至回原来的事件
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;
}
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) {
// View.dispatchTouchEvent(处理事件)
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());
}
// child是容器，ViewGroup.dispatchTouchEvent;child是View，View.dispatchTouchEvent(处理事件)
handled = child.dispatchTouchEvent(transformedEvent);
}
// Done.
transformedEvent.recycle();
return handled;
}
二、在View中处理事件
public boolean dispatchTouchEvent(MotionEvent event) {
// 最前面这一段就是判断当前事件是否能获得焦点，如果不能获得焦点或者不存在一个View，
// 那我们就直接返回False跳出循环
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);
}
//设置返回的默认值，判断时间是否消费
boolean result = false;
//这段是系统调试方面，可以直接忽略
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
//Android用一个32位的整型值表示一次TouchEvent事件,低8位表示touch事件的具体动作，
// 比如按下，抬起，滑动，还有多点触控时的按下，抬起，这个和单点是区分开的，下面看具体的方法:
//1 getAction:触摸动作的原始32位信息，包括事件的动作，触控点信息
//2 getActionMasked:触摸的动作,按下，抬起，滑动，多点按下，多点抬起
//3 getActionIndex:触控点信息
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// 当我们手指按到View上时,其他的依赖滑动都要先停下
stopNestedScroll();
}
//过滤掉一些不合法的事件,比如当前的View的窗口被遮挡了。
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//ListenerInfo 是view的一个内部类 里面有各种各样的listener
ListenerInfo li = mListenerInfo;
//判断是否执行 OnTouch 事件
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
//事件消费
result = true;
}
//onTouch 返回 false 执行，即事件没有消费
if (!result && onTouchEvent(event)) {
//事件消费
result = true;
}
}
if (!result && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
// 如果这是手势的结尾，则在嵌套滚动后清理
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
接下来看View#onTouchEvent判断是否消费
public boolean onTouchEvent(MotionEvent event) {
// 获取动作点击屏幕的位置坐标
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
//如果当前View是一个DISABLED状态，且当前View是一个可点击或者是可长按的状态
// 则clickable返回true。表示当前事件在此消耗且不做处理
final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;
//如果当前View状态为DISABLED
if ((viewFlags & ENABLED_MASK) == DISABLED) {
//如果View的状态是被按压过，且当抬起事件产生，重置View状态为未按压，刷新Drawable的状态
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;
}
// 如果设置了触摸代理
if (mTouchDelegate != null) {
//就交给mTouchDelegate.onTouchEvent处理，如果返回true，则事件被处理了，则不会向下传递
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
//如果当前View的状态是可点击或者是可长按的，就对事件流进行细节处理
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_UP:
//如果是抬起的手势
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
//清除各种状态
if (!clickable) {
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
//prepressed指的是，如果view包裹在一个scrolling View中，可能会进行滑动处理，
// 所以设置了一个prePress的状态
//大致是等待一定时间，然后没有被父类拦截了事件，则认为是点击到了当前的view,从而显示点击态
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
//如果是pressed状态或者是prepressed状态，才进行处理
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// 如果设定了获取焦点，那么调用requestFocus获得焦点
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
////在释放之前给用户显示View的prepressed的状态，状态需要改变为PRESSED，
// 并且需要将背景变为按下的状态为了让用户感知到
if (prepressed) {
setPressed(true, x, y);
}
//是否处理过长按操作了，如果是，则直接返回
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// 如果不是长按的话，仅仅是一个Tap，所以移除长按的回调
//因为没有收到长按事件的延时回调信息，所以这个事件是onClick事件
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
//UI子线程去执行click，为了让click事件开始的时候其他视觉发生变化不影响。
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
//如果post消息失败，直接调用处理click事件
if (!post(mPerformClick)) {
performClickInternal();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
if (prepressed) {
//ViewConfiguration.getPressedStateDuration() 获得的是按下效果显示的时间
//由PRESSED_STATE_DURATION常量指定,目的是让用户感知到click的效果
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
// 如果通过post(Runnable runnable)方式调用失败，则直接调用
mUnsetPressedState.run();
}
//移除Tap的回调 重置View的状态
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_DOWN:
//如果是按下的手势
if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {
mPrivateFlags3 |= PFLAG3_FINGER_DOWN;
}
//在触摸事件中执行按钮相关的动作,如果返回true则表示已经消耗了down
mHasPerformedLongPress = false;
if (!clickable) {
//仅在View支持长按时执行有效，否则直接退出方法
checkForLongClick(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
break;
}
//处理如鼠标的右键的
if (performButtonActionOnTouchDown(event)) {
break;
}
//判断当前view是否是在滚动器当中
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;
//将view的状态变为PREPRESSED，检测是Tap还是长按事件
if (mPendingCheckForTap == null) {
mPendingCheckForTap = new CheckForTap();
}
//如果是在滚动器当中，在滚动器当中的话延迟返回事件，
// 延迟时间为 ViewConfiguration.getTapTimeout()=100毫秒
//在给定的tapTimeout时间之内,用户的触摸没有移动,就当作用户是想点击,而不是滑动.
mPendingCheckForTap.x = event.getX();
mPendingCheckForTap.y = event.getY();
//长按事件的延时回调，最终决定是否是长按事件
postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
} else {
// Not inside a scrolling container, so show the feedback right away
setPressed(true, x, y);
checkForLongClick(
// 长按事件处理，=< 29 延时500ms，>29 延时 400ms
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
break;
case MotionEvent.ACTION_CANCEL:
//接收到系统发出的ACTION_CANCLE事件时，重置状态， 将所有的状态设置为最初始
if (clickable) {
setPressed(false);
}
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
break;
case MotionEvent.ACTION_MOVE:
if (clickable) {
//将实时位置传递给背景（前景）图片
drawableHotspotChanged(x, y);
}
final int motionClassification = event.getClassification();
final boolean ambiguousGesture =
motionClassification == MotionEvent.CLASSIFICATION_AMBIGUOUS_GESTURE;
int touchSlop = mTouchSlop;
if (ambiguousGesture && hasPendingLongPressCallback()) {
if (!pointInView(x, y, touchSlop)) {
// 移除长按事件
removeLongPressCallback();
long delay = (long) (ViewConfiguration.getLongPressTimeout()
* mAmbiguousGestureMultiplier); //长按事件的延时延长一倍
delay -= event.getEventTime() - event.getDownTime();
checkForLongClick( //重新计算长按的延时时间
delay,
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
touchSlop *= mAmbiguousGestureMultiplier;
}
// 判断当前滑动事件是否还在当前view当中，不是就执行下面的方法
//在里面决定移除view后，这个view不会响应onClick事件的原因
if (!pointInView(x, y, touchSlop)) {
// 移除PREPRESSED状态和对应回调s
removeTapCallback();
removeLongPressCallback(); //移除长按事件
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
//是PRESSED就移除长按检测，并移除PRESSED状态
//设置 false 后在 UP事件中就不会执行 PerformClick的onClick事件了
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;
}
return true;
}
return false;
}
三、onTouch 和 onClick 执行的位置和关系
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
}
});
btn.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
//当返回 true, onClick不会执行
//当返回 false, onClick会执行
return false;
}
});
事件关系
当 onTouch 返回 true, onClick不会执行
当 onTouch 返回 false, onClick会执行
1.1、源码流程
我们从View的dispatchTouchEvent处事件处理开始分析
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) {
// 如果是Down停止滚动
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//ListenerInfo 里面存储初始化的事件
ListenerInfo li = mListenerInfo;
//ListenerInfo ， mOnTouchListener 非空执行 onTouch 事件
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
//执行 onTouch 事件
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//短路与，当result 为true ，onTouchEvent不执行
//在 onTouchEvent 里面会处理 onClick 事件
if (!result && onTouchEvent(event)) {
result = true;
}
}
if (!result && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
// of the gesture.
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
执行点击事件，调用View的内部类PerformClick
private final class PerformClick implements Runnable {
@Override
public void run() {
recordGestureClassification(TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__SINGLE_TAP);
performClickInternal();
}
}
private boolean performClickInternal() {
// be interested on.
notifyAutofillManagerOnClick();
return performClick();
}
在View#onTouchEvent里面的ACTION_UP事件中处理点击事件的
case MotionEvent.ACTION_UP:
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
if (!clickable) {
//清除各种状态
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
//prepressed指的是，如果view包裹在一个scrolling View中，
//可能会进行滑动处理，所以设置了一个prePress的状态
//大致是等待一定时间，然后没有被父类拦截了事件，
//则认为是点击到了当前的view,从而显示点击态
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// 如果设定了获取焦点，那么调用requestFocus获得焦点
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
//在释放之前给用户显示View的prepressed的状态，状态需要改变为PRESSED，
//并且需要将背景变为按下的状态为了让用户感知到
if (prepressed) {
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
//如果不是长按的话，仅仅是一个Tap，所以移除长按的回调
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
// UI子线程去执行click，为了让click事件开始的时候其他视觉发生变化不影响
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
//如果post消息失败，直接调用处理click事件
if (!post(mPerformClick)) {
performClickInternal();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
if (prepressed) {
//ViewConfiguration.getPressedStateDuration() 获得的是按下效果显示的时间,
//由PRESSED_STATE_DURATION = 64 常量指定，单位为毫秒
//目的是让用户感知到click的效果
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
//如果通过post(Runnable runnable)方式调用失败，则直接调用
mUnsetPressedState.run();
}
//移除Tap的回调 重置View的状态
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
在 post 方法中发送消息
public boolean post(Runnable action) {
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
return attachInfo.mHandler.post(action);
}
getRunQueue().post(action);
return true;
}
点击事件最终在View#performClick()方法中执行
public boolean performClick() {
notifyAutofillManagerOnClick();
final boolean result;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
//执行onClick事件
li.mOnClickListener.onClick(this);
result = true;
} else {
result = false;
}
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
notifyEnterOrExitForAutoFillIfNeeded(true);
return result;
}