關(guān)于android的觸摸事件這個知識點，一直感覺掌握不牢固淡诗，趁著前幾天有空絮姆，就仔細了看了一遍源碼，順便寫了一下筆記蓖宦，本來不想發(fā)成博客，但考慮到有些可能分析的不對油猫，所以發(fā)出來稠茂，希望大家多多指出問題，如果對你有少許的幫助，那就太好了睬关。
本篇文章是基于android sdk 25的分析诱担。
github
ACTION_DOWN或ACTION_POINTER_DOWN和ACTION_HOVER_MOVE 這三個事件稱為初始事件，因為只有在分發(fā)這三個事件時候电爹，才會處理觸摸目標蔫仙。
ACTION_POINTER_DOWN和ACTION_HOVER_MOVE這兩個稱為多指初始事件。
觸摸目標指消費了初始事件的子視圖丐箩，數(shù)據(jù)結(jié)構(gòu)為鏈表摇邦。新增加的子視圖為存放在頭部。
viewFlags & CLICKABLE == CLICKABLE || viewFlags & LONG_CLICKABLE == LONG_CLICKABLE || viewFlags & CONTEXT_CLICKABLE == CONTEXT_CLICKABLE 表示該視圖是 "可點擊的"屎勘。
- Android的Touch事件由Activity->ViewGroup-View按順序分發(fā)(這里只關(guān)心到Activity)
- 父視圖可以通過
onInterceptTouchEvent來攔截事件分發(fā)到子視圖 - 子視圖可以調(diào)用
requestDisallowInterceptTouchEvent來禁止父視圖攔截事件施籍，但在ACTION_DOWN時，會清除該標記概漱，即只在ACTION_DOWN時丑慎，調(diào)用該方法沒有效果。 - 如果子視圖沒有調(diào)用
requestDisallowInterceptTouchEvent犀概，那么父視圖任何時候都可以攔截事件立哑，即使子視圖已經(jīng)消費了ACTION_DOWN，攔截事件后姻灶，會向子視圖分發(fā)一個ACTION_CANCEL事件 - 父視圖分發(fā)事件時铛绰，只會在初始事件時候，來設(shè)置觸摸目標产喉。即如果子視圖沒消費這三個事件捂掰，也不會接收到后續(xù)的事件。
- 當分發(fā)多指初始事件時曾沈，沒有新的子視圖來消費該事件時这嚣，會將該事件的指針賦予觸摸目標的尾部。
- 當沒有子視圖來消費事件時塞俱，會將事件分發(fā)給父視圖姐帚。(super.dispatchTouchEvent)
- View的事件分發(fā)，OnTouchListener.onTouch -> onTouchEvent -> TouchDelegate.onTouchEvent -> onClick/onLongClick等等
- 只要視圖是可點擊的就默認會消費事件障涯，即使該視圖是不啟用的(setEnabled(false))罐旗，只是不做點擊處理反應(yīng)。
Activity中
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
//用戶交互回調(diào)
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
//window是否消費該事件,touch事件分發(fā)從這里開始
return true;
}
//當前view沒有消費事件唯蝶，則由activity處理
return onTouchEvent(ev);
}
//當前沒有任何view去消費事件時
public boolean onTouchEvent(MotionEvent event) {
//window是否消費該事件九秀，來關(guān)閉當前window
if (mWindow.shouldCloseOnTouch(this, event)) {
finish();
return true;
}
return false;
}
PhoneWindow中
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
//window將事件委托給DecorView分發(fā)
return mDecor.superDispatchTouchEvent(event);
}
DecorView中
public boolean superDispatchTouchEvent(MotionEvent event) {
//調(diào)用父類的dispatchTouchEvent進行分發(fā)
return super.dispatchTouchEvent(event);
}
ViewGroup中
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//輸入事件一致性驗證者
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.
//輔助功能處理
if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
ev.setTargetAccessibilityFocus(false);
}
//從這里開始事件分發(fā)
boolean handled = false;
//安全策略過濾
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
//多指處理
//多指情況下，POINTER:指針粘我。(可以理解為單個手指)
final int actionMasked = action & MotionEvent.ACTION_MASK;
// Handle an initial down.
//處理一個初始按下事件ACTION_DOWN
if (actionMasked == MotionEvent.ACTION_DOWN) {
//丟棄之前的狀態(tài)
// 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.
//取消鼓蜒，清除所有的觸摸目標
cancelAndClearTouchTargets(ev);
//重置觸摸狀態(tài)，這里會將使用requestDisallowInterceptTouchEvent設(shè)置的狀態(tài)清除
//這個狀態(tài)可以阻止父視圖(通過onInterceptTouchEvent)攔截子視圖Touch事件
resetTouchState();
}
// Check for interception.
//檢查是否攔截
final boolean intercepted;
//當為ACTION_DEON事件或觸摸目標為不為null
//即使已經(jīng)有子視圖消費了事件，依然會執(zhí)行判斷
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
//檢查子視圖是否調(diào)用了requestDisallowInterceptTouchEvent來禁止父視圖攔截
//這個標記為ACTION_DOWN處理中被清除都弹，即子視圖在ACTION_DOWN中調(diào)用是不起作用
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
//檢查當前父視圖是否攔截該事件
intercepted = onInterceptTouchEvent(ev);
//恢復(fù)action娇豫，以防止在onInterceptTouchEvent被改變
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.
//當前不是ACTION_DOWN事件，且沒有觸摸目標
//即子視圖如果不消費ACTION_DOWN畅厢，那么后續(xù)事件也不會分發(fā)到锤躁。
intercepted = true;
}
// If intercepted, start normal event dispatch. Also if there is already
// a view that is handling the gesture, do normal event dispatch.
//輔助功能
if (intercepted || mFirstTouchTarget != null) {
ev.setTargetAccessibilityFocus(false);
}
// Check for cancelation.
//檢查是否為ACTION_CANCEL事件
final boolean canceled = resetCancelNextUpFlag(this)
|| actionMasked == MotionEvent.ACTION_CANCEL;
// Update list of touch targets for pointer down, if needed.
//檢查是否把事件分發(fā)給多個子視圖
//通過setMotionEventSplittingEnabled設(shè)置，Android3.0以上默認開啟
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
//當事件不取消而且不攔截
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.
//輔助功能
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
//1.當ACTION_DOWN事件(第一次按下)
//2.或事件可以分發(fā)給多個子視圖且ACTION+POINTER_DOWN(多指處理或详，當主指針還沒結(jié)束，又按下一個指針)
//3.或多指情況下郭计，指針移動
//這里的判斷表示霸琴，只有在ACTION_DOWN或者當前事件分發(fā)還沒結(jié)束，出現(xiàn)新的指針事件才會進行分發(fā)昭伸。但這里的前提依然是梧乘，事件未取消和父視圖不攔截，和至少接收了ACTION_DOWN事件(即觸摸目標鏈表不為空庐杨，ACTION_DOWN事件除外)
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
//獲取事件的指針索引
final int actionIndex = ev.getActionIndex(); // always 0 for down
//指針id的位掩碼(用于獲取觸摸目標捕獲的指針)
//TouchTarget.pointerIdBis 指針id的組合位掩碼选调，用于目標捕獲的所有指針
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.
//清除這個指針作用的早先的觸摸目標
removePointersFromTouchTargets(idBitsToAssign);
final int childrenCount = mChildrenCount;
//掃描可以接收事件的子視圖
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.
//獲取子視圖的事件分發(fā)列表
//這里考慮了自定義的子視圖繪制順序
final ArrayList<View> preorderedList = buildTouchDispatchChildList();
//TODO:按buildTouchDispatchChildList()的返回 != null，即customOrder永遠為false灵份，即自定義了繪制順序也不會改變事件分發(fā)順序
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.
//輔助功能
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - 1;
}
//檢查子視圖是否可以接受事件和觸摸事件是否作用在子視圖上
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
//檢查當前子視圖是否已經(jīng)存在觸摸目標鏈表中
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.
//如果已經(jīng)存在仁堪，則將新指針id賦值給它，并退出循環(huán)
newTouchTarget.pointerIdBits |= idBitsToAssign;
break;
}
//檢查是否設(shè)置了取消標記
//TODO:但這里沒對結(jié)果進行處理
resetCancelNextUpFlag(child);
//在這里將事件交予子視圖進行分發(fā)
//一般能執(zhí)行到這里的:
//1.ACTION_DOWN
//2.多指情況下填渠，指針作用于"新"視圖上
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
//如果子視圖消費了事件
// Child wants to receive touch within its bounds.
//保存一些值
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();
//設(shè)置接收事件的子視圖為新的觸摸目標弦聂，并設(shè)置為觸摸目標鏈表的頭
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.
//當觸摸目標鏈表不為空，且當前事件沒有產(chǎn)生新的觸摸目標(包含已有的觸摸目標)來接收
newTouchTarget = mFirstTouchTarget;
while (newTouchTarget.next != null) {
newTouchTarget = newTouchTarget.next;
}
//找到觸摸目標鏈表的尾部氛什，將指針作用于它
newTouchTarget.pointerIdBits |= idBitsToAssign;
}
}
}
// Dispatch to touch targets.
//除了ACTION_DOWN莺葫，ACTION_POINTER_DOWN,ACTION_HOVER_MOVE
//其他的事件的分發(fā)都從這里
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
//沒有子視圖接收事件，將事件分發(fā)給當前視圖
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.
//將事件分發(fā)給觸摸目標枪眉，除了新的觸摸目標捺檬，因為在之前已經(jīng)分發(fā)了
TouchTarget predecessor = null;
TouchTarget target = mFirstTouchTarget;
while (target != null) {
final TouchTarget next = target.next;
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
//新的觸摸目標，直接跳過
handled = true;
} else {
//檢查事件是否被取消或者被攔截
//即使子視圖在ACTION_DOWN中接收了事件贸铜，如果沒禁止攔截堡纬，父視圖依然可以攔截事件
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
//分發(fā)到觸摸目標
//當cancelChild=true,會分發(fā)ACTION_CANCEL事件
//dispatchTransformedTouchEvent中會判斷當前觸摸目標是否包含指針id
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
//當事件被取消，清除觸摸目標鏈表
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;
}
//取消和清除所有觸摸目標
private void cancelAndClearTouchTargets(MotionEvent event) {
if (mFirstTouchTarget != null) {
boolean syntheticEvent = false;
if (event == null) {
final long now = SystemClock.uptimeMillis();
//獲取一個ACTION_CANCEL事件
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);
//分發(fā)ACTION_CANCEL事件
dispatchTransformedTouchEvent(event, true, target.child, target.pointerIdBits);
}
clearTouchTargets();
if (syntheticEvent) {
event.recycle();
}
}
}
//清除所有觸摸目標
private void clearTouchTargets() {
TouchTarget target = mFirstTouchTarget;
if (target != null) {
do {
TouchTarget next = target.next;
target.recycle();
target = next;
} while (target != null);
mFirstTouchTarget = null;
}
}
//將事件分發(fā)到相應(yīng)的目標
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.
//當事件取消時萨脑，會根據(jù)是否有觸摸目標隐轩，向當前視圖或子視圖分發(fā)一個ACTION_CANCEL事件
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.
//計算要傳遞的指針
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.
//該觸摸目標不包含該指針,不分發(fā)
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.
//將事件進行分發(fā)，根據(jù)是否有觸摸目標
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) {
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());
}
handled = child.dispatchTouchEvent(transformedEvent);
}
// Done.
transformedEvent.recycle();
return handled;
}
View中
public boolean dispatchTouchEvent(MotionEvent event) {
//輔助功能
// 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;
//調(diào)試作用
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Defensive cleanup for new gesture
//停止嵌套滾動
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
//安全策略過濾
//處理拖動滾動條
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//noinspection SimplifiableIfStatement
//先調(diào)用OnTouchListener回調(diào)
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//如果沒有OnTouchListener或者沒有消費渤早，則調(diào)用onTouchEvent
if (!result && onTouchEvent(event)) {
result = true;
}
}
//調(diào)試
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.
//當ACTION_UP职车，ACTION_CANCEL或ACTION_DOWN且不消費，停止嵌套滾動
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();
if ((viewFlags & ENABLED_MASK) == DISABLED) {
//當該視圖不啟用時(setEnabled(false))
if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
// A disabled view that is clickable still consumes the touch
// events, it just doesn't respond to them.
//不啟用的視圖依然可以消費事件，只是沒有反應(yīng)而已悴灵。
//只要該視圖是 "可點擊的"
return (((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
}
//調(diào)用TouchDelegate
if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
(viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {
//該視圖是 "可點擊的"
switch (action) {
case MotionEvent.ACTION_UP:
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
//當我們設(shè)置 "按下" 狀態(tài)或 "延時按下" 狀態(tài)
// take focus if we don't have it already and we should in
// touch mode.
//獲取焦點
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.
//如果設(shè)置了 "延時按下" 狀態(tài)扛芽，那在實際釋放之前設(shè)置為 "按下" 狀態(tài)
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
//如果沒有調(diào)用長按動作而且不忽略下一個抬起的事件，清除長按回調(diào)积瞒，不回調(diào)長按事件
// This is a tap, so remove the longpress check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
//獲取不了焦點川尖，表示正在按下狀態(tài)，才處理點擊事件
// 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)) {
performClick();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
//清除 "按下" 狀態(tài)
if (prepressed) {
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
// If the post failed, unpress right now
mUnsetPressedState.run();
}
//取消點擊檢測計時器茫孔。即 "延時按下" 狀態(tài)
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_DOWN:
mHasPerformedLongPress = false;
//執(zhí)行按鈕的相關(guān)操作
//比如菜單欄點擊
if (performButtonActionOnTouchDown(event)) {
break;
}
// Walk up the hierarchy to determine if we're inside a scrolling container.
//檢查當前是否位于滾動容器中
boolean isInScrollingContainer = isInScrollingContainer();
// For views inside a scrolling container, delay the pressed feedback for
// a short period in case this is a scroll.
//當父視圖處于滾動中叮喳，則延時處理 "按下" 狀態(tài)
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:
//當事件取消時候，清理
setPressed(false);
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_MOVE:
drawableHotspotChanged(x, y);
// Be lenient about moving outside of buttons
//當手指移動時候缰贝，不再處于當前視圖范圍馍悟，取消事件
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
removeTapCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
// Remove any future long press/tap checks
removeLongPressCallback();
setPressed(false);
}
}
break;
}
//不管有沒有處理，只要該視圖具有 "可點擊" 剩晴，就會默認消費掉該事件
//即使該視圖不啟用锣咒，依然會消費事件，只是不執(zhí)行 "點擊" 事件赞弥。
return true;
}
return false;
}
