昨天寫(xiě)完了Android觸摸事件（下）——事件的分發(fā)，寫(xiě)完后以為這一部分終將告一段落了。今早無(wú)意間突然想起茂嗓，好像關(guān)于點(diǎn)擊事件、長(zhǎng)按事件這一部分并沒(méi)有分析翱嫡弧！喷橙！垂死病中驚坐起啥么，粗略的看了下源碼，好像沒(méi)啥東西啊贰逾。仔細(xì)看看吧悬荣，發(fā)現(xiàn)有些地方真的是叫人頭疼。沒(méi)辦法疙剑，仔細(xì)看吧看吧氯迂。正是：
碼中自有顏如玉，碼中自有黃金屋言缤。
onTouchEvent會(huì)遲到嚼蚀，有時(shí)也會(huì)缺席
Android觸摸事件（下）——事件的分發(fā)中寫(xiě)過(guò)：
- 如果設(shè)置了OnTouchListener，那么在執(zhí)行過(guò)程中會(huì)先執(zhí)行OnTouchListener的onTouch方法管挟，接著根據(jù)返回值來(lái)確定是否需要執(zhí)行onTouchEvent方法轿曙。
- onTouchEvent是否需要調(diào)用是和result的值有關(guān)：如果result為true，則不調(diào)用；反之导帝，則調(diào)用守谓。
所以說(shuō)：onTouchEvent會(huì)遲到，有時(shí)也會(huì)缺席您单。不過(guò)缺席的時(shí)候并不是我們關(guān)心的斋荞，我們需要看下正常流程中onTouchEvent到底做了什么：
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
// 判斷是否可以點(diǎn)擊
final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;
// View是否不可用：如果不可用，返回值是是否可點(diǎn)擊
// 注釋：不可用的但是可點(diǎn)擊的View仍然可以接收觸摸事件睹限，僅僅是不響應(yīng)他們
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;
}
}
// 可點(diǎn)擊或者有標(biāo)志位TOOLTIP
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
// 抬起時(shí)進(jìn)行的操作譬猫，這里面有點(diǎn)擊事件的調(diào)用
case MotionEvent.ACTION_UP:
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
// 如果不可點(diǎn)擊，則需要把callBack移除
if (!clickable) {
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
// 這里Prepressed也用于識(shí)別快速按下
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
// 如果按下或者快速按下
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// take focus if we don't have it already and we should in
// touch mode.
// 如果我們沒(méi)有獲得焦點(diǎn)羡疗，那么我們要根據(jù)觸摸模式來(lái)判斷是否可以獲得焦點(diǎn)
// 這里問(wèn)題比較多，后面會(huì)說(shuō)
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.
// 按下按鈕之前别洪，我們已經(jīng)釋放按鈕叨恨。 現(xiàn)在顯示按下的狀態(tài)（調(diào)度點(diǎn)擊之前），以確保用戶看到它挖垛。
setPressed(true, x, y);
}
// 如果沒(méi)有執(zhí)行長(zhǎng)按事件并且不忽略下次抬起事件
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
// 這是點(diǎn)擊事件痒钝，所以需要移除掉長(zhǎng)按事件的檢查
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
// 如果當(dāng)前View已經(jīng)獲得焦點(diǎn)或者觸摸模式為false
if (!focusTaken) {
// Use a Runnable and post this rather than calling
// performClick directly. This lets other visual state
// of the view update before click actions start.
// 通過(guò)performClick執(zhí)行click事件
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
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;
// 如果不可點(diǎn)擊，那么檢查長(zhǎng)按事件
if (!clickable) {
checkForLongClick(0, x, y);
break;
}
if (performButtonActionOnTouchDown(event)) {
break;
}
// Walk up the hierarchy to determine if we're inside a scrolling container.
boolean isInScrollingContainer = isInScrollingContainer();
// 如果View在正在滾動(dòng)的容器中痢毒，那么延遲發(fā)送這條消息
// 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
// 不在正在滾動(dòng)的容器中送矩，直接設(shè)置按下，并檢查長(zhǎng)按事件
setPressed(true, x, y);
checkForLongClick(0, x, y);
}
break;
// 取消哪替，移除callBack
case MotionEvent.ACTION_CANCEL:
if (clickable) {
setPressed(false);
}
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
break;
// 移動(dòng)
case MotionEvent.ACTION_MOVE:
if (clickable) {
drawableHotspotChanged(x, y);
}
// Be lenient about moving outside of buttons
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
// Remove any future long press/tap checks
removeTapCallback();
removeLongPressCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
}
break;
}
return true;
}
return false;
}
上面的代碼去除注釋栋荸，去除移動(dòng)和取消動(dòng)作，真正的代碼并不多：
- 判斷View是否不可用：如果不可用凭舶，那么onTouchEvent返回值是否可點(diǎn)擊（clickable ）
- 如果View可以點(diǎn)擊或者有TOOLTIP標(biāo)志位的話晌块，則進(jìn)行對(duì)事件的不同動(dòng)作的處理。
ACTION_DOWN：主要包括了setPressed和checkForLongClick兩個(gè)操作：
-
setPressed用于設(shè)置按下?tīng)顟B(tài)帅霜，此時(shí)PFLAG_PRESSED標(biāo)志位被設(shè)置匆背。 -
checkForLongClick用于檢查L(zhǎng)ongClick是否可以觸發(fā)，以及發(fā)送延遲消息來(lái)響應(yīng)長(zhǎng)按事件身冀。
private void checkForLongClick(int delayOffset, float x, float y) {
// 如果可以長(zhǎng)按
if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
mHasPerformedLongPress = false;
if (mPendingCheckForLongPress == null) {
mPendingCheckForLongPress = new CheckForLongPress();
}
mPendingCheckForLongPress.setAnchor(x, y);
mPendingCheckForLongPress.rememberWindowAttachCount();
// 延遲執(zhí)行CheckForLongPress操作钝尸，時(shí)間默認(rèn)值 DEFAULT_LONG_PRESS_TIMEOUT = 500ms
postDelayed(mPendingCheckForLongPress,
ViewConfiguration.getLongPressTimeout() - delayOffset);
}
}
private final class CheckForLongPress implements Runnable {
private int mOriginalWindowAttachCount;
private float mX;
private float mY;
@Override
public void run() {
if (isPressed() && (mParent != null)
&& mOriginalWindowAttachCount == mWindowAttachCount) {
// 如果長(zhǎng)按事件返回值true，那么設(shè)置mHasPerformedLongPress為true
// 表示已經(jīng)執(zhí)行了長(zhǎng)按事件搂根，并且返回值為true
if (performLongClick(mX, mY)) {
mHasPerformedLongPress = true;
}
}
}
public void setAnchor(float x, float y) {
mX = x;
mY = y;
}
public void rememberWindowAttachCount() {
mOriginalWindowAttachCount = mWindowAttachCount;
}
}
// 執(zhí)行長(zhǎng)按事件
public boolean performLongClick(float x, float y) {
mLongClickX = x;
mLongClickY = y;
// 調(diào)用performLongClick()方法
final boolean handled = performLongClick();
mLongClickX = Float.NaN;
mLongClickY = Float.NaN;
return handled;
}
public boolean performLongClick() {
// 繼續(xù)調(diào)用
return performLongClickInternal(mLongClickX, mLongClickY);
}
// 真正執(zhí)行長(zhǎng)按方法
private boolean performLongClickInternal(float x, float y) {
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_LONG_CLICKED);
boolean handled = false;
// ListenerInfo中mOnLongClickListener屬性是否不為空珍促，不為空則執(zhí)行onLongClick操作，并將返回值賦給handled
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnLongClickListener != null) {
handled = li.mOnLongClickListener.onLongClick(View.this);
}
if (!handled) {
final boolean isAnchored = !Float.isNaN(x) && !Float.isNaN(y);
handled = isAnchored ? showContextMenu(x, y) : showContextMenu();
}
if (handled) {
performHapticFeedback(HapticFeedbackConstants.LONG_PRESS);
}
return handled;
}
執(zhí)行長(zhǎng)按過(guò)程如下：
- 判斷是否可以長(zhǎng)按兄墅，可以的話進(jìn)行下面操作踢星。這里如果先設(shè)置不可長(zhǎng)按又設(shè)置
OnLongClickListener的話，此時(shí)長(zhǎng)按事件仍有效。但是沐悦，如果順序顛倒下的話成洗，就長(zhǎng)按事件就無(wú)效了。 - 如果可以長(zhǎng)按藏否，那么通過(guò)
Handler將CheckForLongPress延遲發(fā)送瓶殃，時(shí)間是時(shí)間默認(rèn)值DEFAULT_LONG_PRESS_TIMEOUT = 500ms。 -
CheckForLongPress在其run方法中會(huì)根據(jù)performLongClick方法的返回值來(lái)設(shè)置mHasPerformedLongPress變量的值副签，這個(gè)變量的值在后面會(huì)用到遥椿，這里先不說(shuō)。 - 接著會(huì)一路調(diào)用最終從
ListenerInfo中獲得OnLongClickListener淆储，如果不為null冠场，則執(zhí)行其onLongClick方法。
ACTION_UP：
- 不可點(diǎn)擊本砰，則需要把callBack移除
- 可以點(diǎn)擊的話碴裙，通過(guò)是否可以點(diǎn)擊（
clickable）、長(zhǎng)按事件的返回值（mHasPerformedLongPress）点额、是否忽略下次抬起（mIgnoreNextUpEvent）以及焦點(diǎn)是否拿到（focusTaken）這四個(gè)值來(lái)判斷可否執(zhí)行click事件舔株。一般來(lái)說(shuō)，大部分博客都會(huì)直接分析performClick過(guò)程还棱，很少會(huì)提到為什么這個(gè)條件會(huì)成立载慈。我這邊深究一下，看下到底為什么能夠執(zhí)行performClick操作：
2.1.prepressed的值(mPrivateFlags & PFLAG_PREPRESSED) != 0珍手，這個(gè)可以在ACTION_DOWN中可以看到賦值办铡，但賦值的情況是在正在滾動(dòng)的容器中。
2.2(mPrivateFlags & PFLAG_PRESSED)此處PFLAG_PRESSED賦值同樣也是在ACTION_DOWN中賦值珠十，與prepressed相反料扰，此時(shí)View不在正在滾動(dòng)的容器中。
2.3focusTaken的值焙蹭，這個(gè)值涉及的東西有點(diǎn)多晒杈。首先判斷條件isFocusable() && isFocusableInTouchMode() && !isFocused()：isFocusable()一般為true；isFocusableInTouchMode()如果不設(shè)置setFocusableInTouchMode(true)的話孔厉，默認(rèn)為false拯钻；isFocused()這個(gè)值需要注意下，此值意思是是否擁有焦點(diǎn)撰豺，但是我們可以看到判斷條件為!isFocused()粪般，所以如果前面條件都為true的情況下，若此時(shí)isFocused()返回true污桦，那么將不會(huì)再次請(qǐng)求焦點(diǎn)亩歹，因?yàn)榇藭r(shí)已經(jīng)擁有焦點(diǎn)，否則，則會(huì)調(diào)用requestFocus獲取焦點(diǎn)小作，并將返回值賦給focusTaken亭姥。
還是來(lái)看下這邊的代碼吧，挺重要的：
private boolean requestFocusNoSearch(int direction, Rect previouslyFocusedRect) {
// need to be focusable
if ((mViewFlags & FOCUSABLE) != FOCUSABLE
|| (mViewFlags & VISIBILITY_MASK) != VISIBLE) {
return false;
}
// need to be focusable in touch mode if in touch mode
if (isInTouchMode() &&
(FOCUSABLE_IN_TOUCH_MODE != (mViewFlags & FOCUSABLE_IN_TOUCH_MODE))) {
return false;
}
// need to not have any parents blocking us
if (hasAncestorThatBlocksDescendantFocus()) {
return false;
}
handleFocusGainInternal(direction, previouslyFocusedRect);
return true;
}
private boolean hasAncestorThatBlocksDescendantFocus() {
final boolean focusableInTouchMode = isFocusableInTouchMode();
ViewParent ancestor = mParent;
// 查找View的父View顾稀，看其是否有FOCUS_BLOCK_DESCENDANTS標(biāo)志位
// 這里出現(xiàn)一個(gè)常用的變量FOCUS_BLOCK_DESCENDANTS达罗，這里是關(guān)于焦點(diǎn)設(shè)置，后面有代碼分析
while (ancestor instanceof ViewGroup) {
final ViewGroup vgAncestor = (ViewGroup) ancestor;
if (vgAncestor.getDescendantFocusability() == ViewGroup.FOCUS_BLOCK_DESCENDANTS
|| (!focusableInTouchMode && vgAncestor.shouldBlockFocusForTouchscreen())) {
return true;
} else {
ancestor = vgAncestor.getParent();
}
}
return false;
}
void handleFocusGainInternal(@FocusRealDirection int direction, Rect previouslyFocusedRect) {
// 如果沒(méi)有獲取到焦點(diǎn)静秆，則設(shè)置獲取焦點(diǎn)
if ((mPrivateFlags & PFLAG_FOCUSED) == 0) {
mPrivateFlags |= PFLAG_FOCUSED;
View oldFocus = (mAttachInfo != null) ? getRootView().findFocus() : null;
if (mParent != null) {
mParent.requestChildFocus(this, this);
updateFocusedInCluster(oldFocus, direction);
}
if (mAttachInfo != null) {
mAttachInfo.mTreeObserver.dispatchOnGlobalFocusChange(oldFocus, this);
}
onFocusChanged(true, direction, previouslyFocusedRect);
refreshDrawableState();
}
}
上面的代碼很容易理解粮揉，為什么需要單獨(dú)看一下呢？首先來(lái)說(shuō)抚笔，如果去請(qǐng)求獲取焦點(diǎn)的話扶认，真正獲取成功后此時(shí)返回值為true，那么根據(jù)后面的判斷條件是不會(huì)執(zhí)行performClick操作的殊橙。這里可以假設(shè)有如下代碼：
protected void onCreate(Bundle savedInstanceState) {
......
View view2 = findViewById(R.id.v_2);
view2.setFocusable(true);
view2.setFocusableInTouchMode(true);
view2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d("fxxk", "view2 onClick");
}
});
......
}
那么按照上面的分析此時(shí)第一次點(diǎn)擊的時(shí)候應(yīng)該會(huì)去請(qǐng)求焦點(diǎn)的蝠引，此時(shí)點(diǎn)擊事件不會(huì)生效。但蛀柴，真的會(huì)這樣嗎？不會(huì)的矫夯，最初我以為也是這樣鸽疾，但是經(jīng)過(guò)測(cè)試發(fā)現(xiàn)：View在設(shè)置成可見(jiàn)（VISIBLE）是，會(huì)調(diào)用mParent.focusableViewAvailable(this);方法训貌。在之前從源碼分析Activity啟動(dòng)時(shí)的生命周期有源碼decor.setVisibility(View.INVISIBLE)制肮，之后會(huì)調(diào)用Activity.makeVisible()將mDecor.setVisibility(View.VISIBLE);，這時(shí)候我們看下setVisibility方法：
@RemotableViewMethod
public void setVisibility(@Visibility int visibility) {
setFlags(visibility, VISIBILITY_MASK);
}
void setFlags(int flags, int mask) {
final boolean accessibilityEnabled =
AccessibilityManager.getInstance(mContext).isEnabled();
final boolean oldIncludeForAccessibility = accessibilityEnabled && includeForAccessibility();
int old = mViewFlags;
mViewFlags = (mViewFlags & ~mask) | (flags & mask);
int changed = mViewFlags ^ old;
if (changed == 0) {
return;
}
......
final int newVisibility = flags & VISIBILITY_MASK;
// 如果新的狀態(tài)是VISIBLE
if (newVisibility == VISIBLE) {
// 如果有改變
if ((changed & VISIBILITY_MASK) != 0) {
/*
* If this view is becoming visible, invalidate it in case it changed while
* it was not visible. Marking it drawn ensures that the invalidation will
* go through.
*/
mPrivateFlags |= PFLAG_DRAWN;
invalidate(true);
needGlobalAttributesUpdate(true);
// a view becoming visible is worth notifying the parent
// about in case nothing has focus. even if this specific view
// isn't focusable, it may contain something that is, so let
// the root view try to give this focus if nothing else does.
// 這里的DecorView的Parent是ViewRootImpl
if ((mParent != null)) {
// ViewRootImpl的方法
mParent.focusableViewAvailable(this);
}
}
}
......
}
這里偷懶了递沪，把無(wú)關(guān)代碼省去了豺鼻，我們可以看到如果設(shè)置的狀態(tài)和以前不一致的話需要重新根據(jù)狀態(tài)執(zhí)行不同過(guò)程。我們這里設(shè)置的是可見(jiàn)款慨，所以會(huì)執(zhí)行mParent.focusableViewAvailable(this);方法：
ViewRootImpl.java:
@Override
public void focusableViewAvailable(View v) {
checkThread();
if (mView != null) {
// mView是我們的DecorView儒飒，我們并沒(méi)有設(shè)置其獲取焦點(diǎn)
if (!mView.hasFocus()) {
if (sAlwaysAssignFocus) {
// 調(diào)用DecorView的requestFocus方法
v.requestFocus();
}
} else {
// the one case where will transfer focus away from the current one
// is if the current view is a view group that prefers to give focus
// to its children first AND the view is a descendant of it.
View focused = mView.findFocus();
if (focused instanceof ViewGroup) {
ViewGroup group = (ViewGroup) focused;
if (group.getDescendantFocusability() == ViewGroup.FOCUS_AFTER_DESCENDANTS
&& isViewDescendantOf(v, focused)) {
v.requestFocus();
}
}
}
}
}
requestFocus會(huì)調(diào)用requestFocus(int direction, Rect previouslyFocusedRect)方法，在ViewGroup中重寫(xiě)檩奠，這里著重看下桩了。
ViewGroup.java:
@Override
public boolean requestFocus(int direction, Rect previouslyFocusedRect) {
int descendantFocusability = getDescendantFocusability();
switch (descendantFocusability) {
case FOCUS_BLOCK_DESCENDANTS:
// 直接去調(diào)用View的requestFocus，不管子View
return super.requestFocus(direction, previouslyFocusedRect);
case FOCUS_BEFORE_DESCENDANTS: {
// 先于子View請(qǐng)求獲取焦點(diǎn)埠戳，如果自身獲取焦點(diǎn)成功井誉，子View不會(huì)請(qǐng)求獲取焦點(diǎn)
final boolean took = super.requestFocus(direction, previouslyFocusedRect);
return took ? took : onRequestFocusInDescendants(direction, previouslyFocusedRect);
}
case FOCUS_AFTER_DESCENDANTS: {
// 先讓子View請(qǐng)求獲取焦點(diǎn)，如果子View獲取焦點(diǎn)成功整胃，那么父View不會(huì)請(qǐng)求獲取焦點(diǎn)
final boolean took = onRequestFocusInDescendants(direction, previouslyFocusedRect);
return took ? took : super.requestFocus(direction, previouslyFocusedRect);
}
default:
throw new IllegalStateException("descendant focusability must be "
+ "one of FOCUS_BEFORE_DESCENDANTS, FOCUS_AFTER_DESCENDANTS, FOCUS_BLOCK_DESCENDANTS "
+ "but is " + descendantFocusability);
}
}
ViewGroup.java:
protected boolean onRequestFocusInDescendants(int direction,
Rect previouslyFocusedRect) {
int index;
int increment;
int end;
int count = mChildrenCount;
if ((direction & FOCUS_FORWARD) != 0) {
index = 0;
increment = 1;
end = count;
} else {
index = count - 1;
increment = -1;
end = -1;
}
final View[] children = mChildren;
for (int i = index; i != end; i += increment) {
View child = children[i];
// 只對(duì)可見(jiàn)的View請(qǐng)求獲取焦點(diǎn)颗圣，并且一旦有View獲取焦點(diǎn)則不會(huì)讓其他View請(qǐng)求獲取焦點(diǎn)
if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
if (child.requestFocus(direction, previouslyFocusedRect)) {
return true;
}
}
}
return false;
}
ViewGroup獲取焦點(diǎn)時(shí)需要根據(jù)descendantFocusability的值來(lái)判斷，這里descendantFocusability可能出現(xiàn)三個(gè)值：
- FOCUS_BLOCK_DESCENDANTS：父View直接請(qǐng)求獲取焦點(diǎn)。
- FOCUS_BEFORE_DESCENDANTS：父View會(huì)優(yōu)先其子View在岂，請(qǐng)求獲取焦點(diǎn)奔则，如果沒(méi)有獲取到焦點(diǎn)，則會(huì)讓其子View請(qǐng)求獲取焦點(diǎn)洁段。
- FOCUS_AFTER_DESCENDANTS：與FOCUS_BEFORE_DESCENDANTS相反应狱，子View會(huì)先請(qǐng)求獲取焦點(diǎn)，如果獲取到焦點(diǎn)祠丝，那么父View不會(huì)請(qǐng)求獲取焦點(diǎn)疾呻。
默認(rèn)情況ViewGroup在初始化的時(shí)候設(shè)置為FOCUS_BEFORE_DESCENDANTS，但是DecorView設(shè)置為FOCUS_AFTER_DESCENDANTS
好了写半，到這里我們知道為什么剛才的代碼可以執(zhí)行點(diǎn)擊事件了岸蜗。不過(guò)，如果改成下面的代碼執(zhí)行結(jié)果需要自己試試了：
此時(shí)叠蝇，點(diǎn)擊事件執(zhí)行會(huì)出現(xiàn)：View1獲取焦點(diǎn)后璃岳，點(diǎn)擊正常，點(diǎn)擊View2悔捶，無(wú)反應(yīng)铃慷，再次點(diǎn)擊事件正常。
我們接著分析繼續(xù)來(lái)：
這次我們知道條件成立后會(huì)通過(guò)
Handler發(fā)送PerformClick對(duì)象蜕该，如果發(fā)送成功犁柜，則執(zhí)行PerformClick.run方法，否則執(zhí)行performClick()方法（PerformClick.run也調(diào)用了performClick方法）堂淡，最終執(zhí)行OnClickListener的onClick方法馋缅。
performClick
總結(jié)
寫(xiě)了這么多，還是來(lái)個(gè)總結(jié)吧：
- 在按下的時(shí)候绢淀，如果長(zhǎng)按事件執(zhí)行了萤悴，并且返回值為false，那么此時(shí)點(diǎn)擊事件不會(huì)執(zhí)行皆的；反之則會(huì)執(zhí)行點(diǎn)擊事件覆履。
-
關(guān)于ViewGroup和子View獲取焦點(diǎn)的先后順序，根據(jù)
descendantFocusability的值來(lái)判斷：
FOCUS_BLOCK_DESCENDANTS：父View直接請(qǐng)求獲取焦點(diǎn)祭务。
FOCUS_BEFORE_DESCENDANTS：父View會(huì)優(yōu)先其子View内狗，請(qǐng)求獲取焦點(diǎn)，如果沒(méi)有獲取到焦點(diǎn)义锥，則會(huì)讓其子View請(qǐng)求獲取焦點(diǎn)柳沙。
FOCUS_AFTER_DESCENDANTS：與FOCUS_BEFORE_DESCENDANTS相反，子View會(huì)先請(qǐng)求獲取焦點(diǎn)拌倍，如果獲取到焦點(diǎn)赂鲤，那么父View不會(huì)請(qǐng)求獲取焦點(diǎn)噪径。 - 如果同一個(gè)頁(yè)面中，有多個(gè)View都可以獲得焦點(diǎn)数初，那么只有當(dāng)前獲取焦點(diǎn)的點(diǎn)擊事件可以正常執(zhí)行找爱，其他View需要先點(diǎn)擊一次獲取焦點(diǎn)，之后可以正常執(zhí)行點(diǎn)擊事件泡孩。
OK车摄，這篇分析到此結(jié)束了。如果有問(wèn)題仑鸥，請(qǐng)指出（估計(jì)也就是自己來(lái)發(fā)現(xiàn)問(wèn)題吧）吮播。
這里多說(shuō)幾句：之前，我覺(jué)得許多博客分析的真的是頭頭是道眼俊，當(dāng)輪到我去分析某些東西的時(shí)候再去看他們的博客卻發(fā)現(xiàn)：好多東西都說(shuō)的不明確意狠，太模糊。所以疮胖，自己分析的時(shí)候盡量把所有過(guò)程全部分析完成环戈，爭(zhēng)取步驟完整，方便以后自己回顧澎灸。
That's all!
