一、在ViewGroup 事件分發(fā)
ViewGroup#dispatchTouchEvent 分發(fā)事件
public boolean dispatchTouchEvent(MotionEvent ev) {
//驗(yàn)證事件是否連續(xù)
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
}
// 殘障人事的輔助類，智能聊天
if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
ev.setTargetAccessibilityFocus(false);
}
//這個(gè)變量用于記錄事件是否被處理完
boolean handled = false;
//過濾掉一些不合法的事件：當(dāng)前的View的窗口被遮擋了
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
//重置前面為0 ，只留下后八位，用于判斷相等時(shí)候，可以提高性能。
final int actionMasked = action & MotionEvent.ACTION_MASK;
// Handle an initial down.
// 多指還單指，只會(huì)執(zhí)行一次 -- Action_point_donw
// 重置狀態(tài)
if (actionMasked == MotionEvent.ACTION_DOWN) {
cancelAndClearTouchTargets(ev);
resetTouchState();
}
/***********************************第一塊, 檢測(cè)是否攔截*******************************/
// Check for interception.
// 檢測(cè)是否攔截 -- 父容器的權(quán)利
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//判斷允不允許這個(gè)View攔截，在內(nèi)部攔截中子View請(qǐng)求 requestDisallowInterceptTouchEvent
//使用與運(yùn)算作為判斷，可以讓我們?cè)趂lag中，存儲(chǔ)好幾個(gè)標(biāo)志
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
// disallowIntercept 決定 onInterceptTouchEvent 會(huì)不會(huì)執(zhí)行
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
//重新恢復(fù)Action，以免action在上面的步驟被人為地改變了
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被設(shè)置了PFLAG_CANCEL_NEXT_UP_EVENT ,那么就表示，下一步應(yīng)該是Cancel事件
//或者如果當(dāng)前的Action為取消，那么當(dāng)前事件應(yīng)該就是取消了。
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;
// 默認(rèn)情況為true -- 是否可以多指
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0
&& !isMouseEvent;
//新的觸摸對(duì)象，
TouchTarget newTouchTarget = null;
//是否把事件分配給了新的觸摸
boolean alreadyDispatchedToNewTouchTarget = false;
/************************第二塊, 遍歷子View，詢問子View是否處理事件*******************/
// 在 if 中分發(fā)事件
if (!canceled && !intercepted) {
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
// 第一根手指按下時(shí)，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)
// 鼠標(biāo)
|| 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 ，最多識(shí)別多少手指？32位，位運(yùn)算，一位表示一個(gè)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);
// 有多少個(gè)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.
// 將子View 進(jìn)行排序
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
// 倒序遍歷
for (int i = childrenCount - 1; i >= 0; i--) {
final int childIndex = getAndVerifyPreorderedIndex(
childrenCount, i, customOrder);
final View child = getAndVerifyPreorderedView(
preorderedList, children, childIndex);
// 是否能處理點(diǎn)擊事件
// view是否可見或者animotion不為空
if (!child.canReceivePointerEvents()
|| !isTransformedTouchPointInView(x, y, child, null)) {
continue;
}
// 單指操作，為null，多指才不為空
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不在之前的觸摸目標(biāo)列表中，
//先重置childView的標(biāo)志，去除掉CACEL的標(biāo)志
resetCancelNextUpFlag(child);
// 詢問 child 是否處理事件，如果child處理，則命中if -- 遞歸
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();
// 創(chuàng)建了 newTouchTarget == mFirstTouchTarget
newTouchTarget = addTouchTarget(child, idBitsToAssign);
// 后面會(huì)子View處理事件用到
alreadyDispatchedToNewTouchTarget = true;
// 退出循環(huán)，不再循環(huán)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為null，就代表，這個(gè)事件沒有找到子View去處理它，
//那么，如果之前已經(jīng)有了觸摸對(duì)象（比如，我點(diǎn)了一張圖，另一個(gè)手指在外面圖的外面點(diǎn)下去）
//那么就把這個(gè)之前那個(gè)觸摸目標(biāo)定為第一個(gè)觸摸對(duì)象，并且把這個(gè)觸摸（pointer）分配給最近添加的觸摸目標(biāo)
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;
}
}
}
/************************第三塊, 判斷子View處理還是自己處理事件*******************/
// Dispatch to touch targets.
// 沒有child處理事件的時(shí)候
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
// 詢問自己是否處理
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
// 有子View處理了事件
TouchTarget predecessor = null;
TouchTarget target = mFirstTouchTarget;
// while循環(huán)為單指操作時(shí) 只會(huì)執(zhí)行一次
while (target != null) {
// 單指操作 next = null
final TouchTarget next = target.next;
// if命中，直接返回 handle，不作處理。（根據(jù)局部變量 alreadyDispatchedToNewTouchTarget
//確認(rèn)只有Action_Down才能命中
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else { //其他Action 執(zhí)行，如：Action_Move
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
// 詢問 target.child（前面保存的之View）
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
// 為true 取消child處理事件
if (cancelChild) {
if (predecessor == null) {
// mFirstTouchTarget 置為null
mFirstTouchTarget = next;
} else {
predecessor.next = next;
}
//回收內(nèi)存
target.recycle();
//把下一個(gè)賦予現(xiàn)在
target = next;
continue;
}
}
predecessor = target;
target = next;
}
}
// 遇到了取消事件、或者是單點(diǎn)觸摸下情況下手指離開，我們就要更新觸摸的狀態(tài)
if (canceled
|| actionMasked == MotionEvent.ACTION_UP
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
resetTouchState();
} else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {
//如果是多點(diǎn)觸摸下的手指抬起事件，就要根據(jù)idBit從TouchTarget中移除掉對(duì)應(yīng)的Pointer(觸摸點(diǎn))
final int actionIndex = ev.getActionIndex();
final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);
removePointersFromTouchTargets(idBitsToRemove);
}
}
if (!handled && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);
}
return handled;
}
//參數(shù) disallowIntercept 為 true 讓parent 不攔截
//參數(shù) disallowIntercept 為 fslse 讓parent 攔截
@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);
}
}
可見ViewGroup#dispatchTouchEvent分為三部分
- 1、是否攔截子View,intercepted為true攔截，為false 不攔截
- 2、遍歷子View，詢問子View是否處理事件
- 3、如果子View都不處理，詢問自己是否處理事件
1.1、 取消事件和重置狀態(tài)
- 執(zhí)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);
// 執(zhí)行取消事件
dispatchTransformedTouchEvent(event, true, target.child, target.pointerIdBits);
}
// 清除 TouchTarget
clearTouchTargets();
if (syntheticEvent) {
event.recycle();
}
}
}
- 重置狀態(tài)
private void resetTouchState() {
clearTouchTargets();
resetCancelNextUpFlag(this);
// 重置了 mGroupFlags 的值
mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
mNestedScrollAxes = SCROLL_AXIS_NONE;
}
1.2、攔截事件
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;
}
我們?cè)谧远xView 里面可以重寫這個(gè)方法來處理攔截事件
1.3、詢問子View是否處理事件
在里面會(huì)對(duì)子View 根據(jù)懸浮層進(jìn)行排序
public ArrayList<View> buildTouchDispatchChildList() {
return buildOrderedChildList();
}
ArrayList<View> 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];
// 默認(rèn)不設(shè)置，則為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、詢問子View處理，還是自己處理
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();
//當(dāng)取消事件會(huì)執(zhí)行這里，內(nèi)部攔截也會(huì)走
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
//把事件先設(shè)為 ACTION_CANCEL
event.setAction(MotionEvent.ACTION_CANCEL);
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
handled = child.dispatchTouchEvent(event);
}
//設(shè)至回原來的事件
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(處理事件)
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(處理事件)
handled = child.dispatchTouchEvent(transformedEvent);
}
// Done.
transformedEvent.recycle();
return handled;
}
二、在View中處理事件
public boolean dispatchTouchEvent(MotionEvent event) {
// 最前面這一段就是判斷當(dāng)前事件是否能獲得焦點(diǎn)，如果不能獲得焦點(diǎn)或者不存在一個(gè)View，
// 那我們就直接返回False跳出循環(huán)
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);
}
//設(shè)置返回的默認(rèn)值，判斷時(shí)間是否消費(fèi)
boolean result = false;
//這段是系統(tǒng)調(diào)試方面，可以直接忽略
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
//Android用一個(gè)32位的整型值表示一次TouchEvent事件,低8位表示touch事件的具體動(dòng)作，
// 比如按下，抬起，滑動(dòng)，還有多點(diǎn)觸控時(shí)的按下，抬起，這個(gè)和單點(diǎn)是區(qū)分開的，下面看具體的方法:
//1 getAction:觸摸動(dòng)作的原始32位信息，包括事件的動(dòng)作，觸控點(diǎn)信息
//2 getActionMasked:觸摸的動(dòng)作,按下，抬起，滑動(dòng)，多點(diǎn)按下，多點(diǎn)抬起
//3 getActionIndex:觸控點(diǎn)信息
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// 當(dāng)我們手指按到View上時(shí),其他的依賴滑動(dòng)都要先停下
stopNestedScroll();
}
//過濾掉一些不合法的事件,比如當(dāng)前的View的窗口被遮擋了。
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//ListenerInfo 是view的一個(gè)內(nèi)部類 里面有各種各樣的listener
ListenerInfo li = mListenerInfo;
//判斷是否執(zhí)行 OnTouch 事件
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
//事件消費(fèi)
result = true;
}
//onTouch 返回 false 執(zhí)行，即事件沒有消費(fèi)
if (!result && onTouchEvent(event)) {
//事件消費(fèi)
result = true;
}
}
if (!result && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
// 如果這是手勢(shì)的結(jié)尾，則在嵌套滾動(dòng)后清理
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
接下來看View#onTouchEvent判斷是否消費(fèi)
public boolean onTouchEvent(MotionEvent event) {
// 獲取動(dòng)作點(diǎn)擊屏幕的位置坐標(biāo)
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
//如果當(dāng)前View是一個(gè)DISABLED狀態(tài)，且當(dāng)前View是一個(gè)可點(diǎn)擊或者是可長(zhǎng)按的狀態(tài)
// 則clickable返回true。表示當(dāng)前事件在此消耗且不做處理
final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;
//如果當(dāng)前View狀態(tài)為DISABLED
if ((viewFlags & ENABLED_MASK) == DISABLED) {
//如果View的狀態(tài)是被按壓過，且當(dāng)抬起事件產(chǎn)生，重置View狀態(tài)為未按壓，刷新Drawable的狀態(tài)
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;
}
// 如果設(shè)置了觸摸代理
if (mTouchDelegate != null) {
//就交給mTouchDelegate.onTouchEvent處理，如果返回true，則事件被處理了，則不會(huì)向下傳遞
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
//如果當(dāng)前View的狀態(tài)是可點(diǎn)擊或者是可長(zhǎng)按的，就對(duì)事件流進(jìn)行細(xì)節(jié)處理
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_UP:
//如果是抬起的手勢(shì)
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
//清除各種狀態(tài)
if (!clickable) {
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
//prepressed指的是，如果view包裹在一個(gè)scrolling View中，可能會(huì)進(jìn)行滑動(dòng)處理，
// 所以設(shè)置了一個(gè)prePress的狀態(tài)
//大致是等待一定時(shí)間，然后沒有被父類攔截了事件，則認(rèn)為是點(diǎn)擊到了當(dāng)前的view,從而顯示點(diǎn)擊態(tài)
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
//如果是pressed狀態(tài)或者是prepressed狀態(tài)，才進(jìn)行處理
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// 如果設(shè)定了獲取焦點(diǎn)，那么調(diào)用requestFocus獲得焦點(diǎn)
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
////在釋放之前給用戶顯示View的prepressed的狀態(tài)，狀態(tài)需要改變?yōu)镻RESSED，
// 并且需要將背景變?yōu)榘聪碌臓顟B(tài)為了讓用戶感知到
if (prepressed) {
setPressed(true, x, y);
}
//是否處理過長(zhǎng)按操作了，如果是，則直接返回
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// 如果不是長(zhǎng)按的話，僅僅是一個(gè)Tap，所以移除長(zhǎng)按的回調(diào)
//因?yàn)闆]有收到長(zhǎng)按事件的延時(shí)回調(diào)信息，所以這個(gè)事件是onClick事件
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
//UI子線程去執(zhí)行click，為了讓click事件開始的時(shí)候其他視覺發(fā)生變化不影響。
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
//如果post消息失敗，直接調(diào)用處理click事件
if (!post(mPerformClick)) {
performClickInternal();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
if (prepressed) {
//ViewConfiguration.getPressedStateDuration() 獲得的是按下效果顯示的時(shí)間
//由PRESSED_STATE_DURATION常量指定,目的是讓用戶感知到click的效果
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
// 如果通過post(Runnable runnable)方式調(diào)用失敗，則直接調(diào)用
mUnsetPressedState.run();
}
//移除Tap的回調(diào) 重置View的狀態(tài)
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_DOWN:
//如果是按下的手勢(shì)
if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {
mPrivateFlags3 |= PFLAG3_FINGER_DOWN;
}
//在觸摸事件中執(zhí)行按鈕相關(guān)的動(dòng)作,如果返回true則表示已經(jīng)消耗了down
mHasPerformedLongPress = false;
if (!clickable) {
//僅在View支持長(zhǎng)按時(shí)執(zhí)行有效，否則直接退出方法
checkForLongClick(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
break;
}
//處理如鼠標(biāo)的右鍵的
if (performButtonActionOnTouchDown(event)) {
break;
}
//判斷當(dāng)前view是否是在滾動(dòng)器當(dāng)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;
//將view的狀態(tài)變?yōu)镻REPRESSED，檢測(cè)是Tap還是長(zhǎng)按事件
if (mPendingCheckForTap == null) {
mPendingCheckForTap = new CheckForTap();
}
//如果是在滾動(dòng)器當(dāng)中，在滾動(dòng)器當(dāng)中的話延遲返回事件，
// 延遲時(shí)間為 ViewConfiguration.getTapTimeout()=100毫秒
//在給定的tapTimeout時(shí)間之內(nèi),用戶的觸摸沒有移動(dòng),就當(dāng)作用戶是想點(diǎn)擊,而不是滑動(dòng).
mPendingCheckForTap.x = event.getX();
mPendingCheckForTap.y = event.getY();
//長(zhǎng)按事件的延時(shí)回調(diào)，最終決定是否是長(zhǎng)按事件
postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
} else {
// Not inside a scrolling container, so show the feedback right away
setPressed(true, x, y);
checkForLongClick(
// 長(zhǎng)按事件處理，=< 29 延時(shí)500ms，>29 延時(shí) 400ms
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
break;
case MotionEvent.ACTION_CANCEL:
//接收到系統(tǒng)發(fā)出的ACTION_CANCLE事件時(shí)，重置狀態(tài)， 將所有的狀態(tài)設(shè)置為最初始
if (clickable) {
setPressed(false);
}
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
break;
case MotionEvent.ACTION_MOVE:
if (clickable) {
//將實(shí)時(shí)位置傳遞給背景（前景）圖片
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)) {
// 移除長(zhǎng)按事件
removeLongPressCallback();
long delay = (long) (ViewConfiguration.getLongPressTimeout()
* mAmbiguousGestureMultiplier); //長(zhǎng)按事件的延時(shí)延長(zhǎng)一倍
delay -= event.getEventTime() - event.getDownTime();
checkForLongClick( //重新計(jì)算長(zhǎng)按的延時(shí)時(shí)間
delay,
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
touchSlop *= mAmbiguousGestureMultiplier;
}
// 判斷當(dāng)前滑動(dòng)事件是否還在當(dāng)前view當(dāng)中，不是就執(zhí)行下面的方法
//在里面決定移除view后，這個(gè)view不會(huì)響應(yīng)onClick事件的原因
if (!pointInView(x, y, touchSlop)) {
// 移除PREPRESSED狀態(tài)和對(duì)應(yīng)回調(diào)s
removeTapCallback();
removeLongPressCallback(); //移除長(zhǎng)按事件
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
//是PRESSED就移除長(zhǎng)按檢測(cè)，并移除PRESSED狀態(tài)
//設(shè)置 false 后在 UP事件中就不會(huì)執(zhí)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 執(zhí)行的位置和關(guān)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) {
//當(dāng)返回 true, onClick不會(huì)執(zhí)行
//當(dāng)返回 false, onClick會(huì)執(zhí)行
return false;
}
});
事件關(guān)系
當(dāng) onTouch 返回 true, onClick不會(huì)執(zhí)行
當(dāng) onTouch 返回 false, onClick會(huì)執(zhí)行
1.1、源碼流程
我們從View的dispatchTouchEvent處事件處理開始分析
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?jié)L動(dòng)
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//ListenerInfo 里面存儲(chǔ)初始化的事件
ListenerInfo li = mListenerInfo;
//ListenerInfo ， mOnTouchListener 非空?qǐng)?zhí)行 onTouch 事件
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
//執(zhí)行 onTouch 事件
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//短路與，當(dāng)result 為true ，onTouchEvent不執(zhí)行
//在 onTouchEvent 里面會(huì)處理 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;
}
執(zhí)行點(diǎn)擊事件，調(diào)用View的內(nèi)部類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事件中處理點(diǎn)擊事件的
case MotionEvent.ACTION_UP:
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
if (!clickable) {
//清除各種狀態(tài)
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
//prepressed指的是，如果view包裹在一個(gè)scrolling View中，
//可能會(huì)進(jìn)行滑動(dòng)處理，所以設(shè)置了一個(gè)prePress的狀態(tài)
//大致是等待一定時(shí)間，然后沒有被父類攔截了事件，
//則認(rèn)為是點(diǎn)擊到了當(dāng)前的view,從而顯示點(diǎn)擊態(tài)
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// 如果設(shè)定了獲取焦點(diǎn)，那么調(diào)用requestFocus獲得焦點(diǎn)
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
//在釋放之前給用戶顯示View的prepressed的狀態(tài)，狀態(tài)需要改變?yōu)镻RESSED，
//并且需要將背景變?yōu)榘聪碌臓顟B(tài)為了讓用戶感知到
if (prepressed) {
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
//如果不是長(zhǎng)按的話，僅僅是一個(gè)Tap，所以移除長(zhǎng)按的回調(diào)
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
// UI子線程去執(zhí)行click，為了讓click事件開始的時(shí)候其他視覺發(fā)生變化不影響
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
//如果post消息失敗，直接調(diào)用處理click事件
if (!post(mPerformClick)) {
performClickInternal();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
if (prepressed) {
//ViewConfiguration.getPressedStateDuration() 獲得的是按下效果顯示的時(shí)間,
//由PRESSED_STATE_DURATION = 64 常量指定，單位為毫秒
//目的是讓用戶感知到click的效果
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
//如果通過post(Runnable runnable)方式調(diào)用失敗，則直接調(diào)用
mUnsetPressedState.run();
}
//移除Tap的回調(diào) 重置View的狀態(tài)
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
在 post 方法中發(fā)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;
}
點(diǎn)擊事件最終在View#performClick()方法中執(zhí)行
public boolean performClick() {
notifyAutofillManagerOnClick();
final boolean result;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
//執(zhí)行onClick事件
li.mOnClickListener.onClick(this);
result = true;
} else {
result = false;
}
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
notifyEnterOrExitForAutoFillIfNeeded(true);
return result;
}
