對于View的事件分發(fā)，涉及的有dispatchTouchEvent、onTouchEvent、onTouch、onClick
為了更好的查看View的事件轉(zhuǎn)發(fā)，我們先來看個demo
首先定義一個自定義View
public class CustomView extends AppCompatButton {
private static final String TAG = "CustomView";
public CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
LogUtils.e(TAG,"dispatchTouchEvent=ACTION_DOWN");
break;
case MotionEvent.ACTION_MOVE:
LogUtils.e(TAG,"dispatchTouchEvent=ACTION_MOVE");
break;
case MotionEvent.ACTION_UP:
LogUtils.e(TAG,"dispatchTouchEvent=ACTION_UP");
break;
}
return super.dispatchTouchEvent(event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
LogUtils.e(TAG,"onTouchEvent=ACTION_DOWN");
break;
case MotionEvent.ACTION_MOVE:
LogUtils.e(TAG,"onTouchEvent=ACTION_MOVE");
break;
case MotionEvent.ACTION_UP:
LogUtils.e(TAG,"onTouchEvent=ACTION_UP");
break;
}
return super.onTouchEvent(event);
}
}
把自定義的按鈕添加到布局中：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.xiaoma.restudy.customviews.CustomView
android:id="@+id/mbt_cmb"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Custom View" />
</LinearLayout>
</android.support.constraint.ConstraintLayout>
最后看CustomActivity代碼
public class CustomActivity extends BaseActivity {
private CustomView mMbtCmb;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_custom);
initView();
}
@SuppressLint("ClickableViewAccessibility")
private void initView() {
mMbtCmb = (CustomView) findViewById(R.id.mbt_cmb);
mMbtCmb.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
LogUtils.e(TAG, "onTouch=ACTION_DOWN");
break;
case MotionEvent.ACTION_MOVE:
LogUtils.e(TAG, "onTouch=ACTION_MOVE");
break;
case MotionEvent.ACTION_UP:
LogUtils.e(TAG, "onTouch=ACTION_UP");
break;
}
return false;
}
});
mMbtCmb.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
LogUtils.e(TAG, "onClick");
}
});
mMbtCmb.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
LogUtils.e(TAG, "onLongClick");
return false;
}
});
}
}
點(diǎn)擊按鈕后，運(yùn)行的結(jié)果如下
E/CustomView: dispatchTouchEvent=ACTION_DOWN
E/.customviews.CustomActivity: onTouch=ACTION_DOWN
E/CustomView: onTouchEvent=ACTION_DOWN
E/CustomView: dispatchTouchEvent=ACTION_MOVE
E/.customviews.CustomActivity: onTouch=ACTION_MOVE
E/CustomView: onTouchEvent=ACTION_MOVE
E/.customviews.CustomActivity: onLongClick
E/CustomView: dispatchTouchEvent=ACTION_MOVE
E/.customviews.CustomActivity: onTouch=ACTION_MOVE
E/CustomView: onTouchEvent=ACTION_MOVE
E/CustomView: dispatchTouchEvent=ACTION_UP
E/.customviews.CustomActivity: onTouch=ACTION_UP
E/CustomView: onTouchEvent=ACTION_UP
E/.customviews.CustomActivity: onClick
點(diǎn)擊下就可以出現(xiàn)上面日志，否則出現(xiàn)一系列ACTION_MOVE事件；但總結(jié)來看是ACTION_DOWN、ACTION_MOVE、ACTION_UP三個事件的傳遞是dispatchTouchEvent-->onTouch-->onTouchEvent-->onLongClick-->onClick
查看源碼從View的dispatchTouchEvent方法開始，摘抄代碼如下
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//上面沒有沒有消費(fèi)，在onTouchEvent中返回為true進(jìn)行消費(fèi)。
if (!result && onTouchEvent(event)) {
result = true;
}
1、如果onTouchListener不等于null,并且是enabled,且onTouch返回true,則消費(fèi)掉事件
2、上面如果沒有消費(fèi)，則執(zhí)行onTouchEvent，如果返回true,則消費(fèi)掉事件
總結(jié)：也就是說如果onTouch方法返回ture,則不執(zhí)行onTouchEvent方法
View的onTouchEvent方法如下，摘要主要功能如下
final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;
if ((viewFlags & ENABLED_MASK) == DISABLED) {
if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
// A disabled view that is clickable still consumes the touch
// events, it just doesn't respond to them.
return clickable;
}
if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_UP:
break;
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_CANCEL:
break;
case MotionEvent.ACTION_MOVE:
break;
return true;
}
1.clickable變量標(biāo)識如果view是可點(diǎn)擊或者長按的狀態(tài)就是true;
2.如果view是disabled狀態(tài)，不處理事件，返回clickable變量；意味著一個disabled狀態(tài)的view，如果可點(diǎn)擊或者長按，還是消費(fèi)事件，但是不響應(yīng)
3.如果mTouchDlegate不為空，則當(dāng)前view不消費(fèi)事件，交給觸摸代理消費(fèi)事件；
4.如果clickable返回true或者view可以在懸?；蛘唛L按時顯示工具，則view消耗此事件；
查看MotionEvent.ACTION_DOWN事件，源碼如下
case MotionEvent.ACTION_DOWN:
if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {
mPrivateFlags3 |= PFLAG3_FINGER_DOWN;
}
mHasPerformedLongPress = false;
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();
// For views inside a scrolling container, delay the pressed feedback for
// a short period in case this is a scroll.
if (isInScrollingContainer) {
mPrivateFlags |= PFLAG_PREPRESSED;
if (mPendingCheckForTap == null) {
mPendingCheckForTap = new CheckForTap();
}
mPendingCheckForTap.x = event.getX();
mPendingCheckForTap.y = event.getY();
postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
} else {
// Not inside a scrolling container, so show the feedback right away
setPressed(true, x, y);
checkForLongClick(0, x, y);
}
break;
- mHasPerformedLongPress = false; 長按事件還未觸發(fā)
- boolean isInScrollingContainer = isInScrollingContainer(); 判斷是否是個滑動容器
- 如果是滑動容器，設(shè)置 mPrivateFlags |= PFLAG_PREPRESSED; 設(shè)置為預(yù)按狀態(tài);發(fā)送一個延遲為ViewConfiguration.getTapTimeout()=100的消息;如果非滑動容器，則直接設(shè)置為按壓狀態(tài)，且發(fā)送延遲500后執(zhí)行CheckForLongPress()
- 到達(dá)延遲時間后，執(zhí)行CheckForTap()里的run()方法，取消預(yù)按狀態(tài)，且在setPressed(true, x, y)方法里設(shè)置按壓狀態(tài) mPrivateFlags |= PFLAG_PRESSED；且檢查是否有長按事件，如果有再發(fā)送一個延遲為ViewConfiguration.getLongPressTimeout()=500的消息(減去上面的延遲時間)，到達(dá)延遲時間后，執(zhí)行CheckForLongPress()
總結(jié)：100用來檢測是否按壓了，500時長用來檢測是否長按
- 如果設(shè)置了長按的回調(diào)；如果長按的返回值為true,則設(shè)置 mHasPerformedLongPress = true;如果沒有設(shè)置長按回調(diào)或者返回false，則mHasPerformedLongPress依舊等于false;
private final class CheckForTap implements Runnable {
public float x;
public float y;
@Override
public void run() {
mPrivateFlags &= ~PFLAG_PREPRESSED;
setPressed(true, x, y);
checkForLongClick(ViewConfiguration.getTapTimeout(), x, y);
}
}
##################################
private void checkForLongClick(int delayOffset, float x, float y) {
if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE || (mViewFlags & TOOLTIP) == TOOLTIP) {
mHasPerformedLongPress = false;
if (mPendingCheckForLongPress == null) {
mPendingCheckForLongPress = new CheckForLongPress();
}
mPendingCheckForLongPress.setAnchor(x, y);
mPendingCheckForLongPress.rememberWindowAttachCount();
mPendingCheckForLongPress.rememberPressedState();
postDelayed(mPendingCheckForLongPress,
ViewConfiguration.getLongPressTimeout() - delayOffset);
}
}
#################
private final class CheckForLongPress implements Runnable {
private int mOriginalWindowAttachCount;
private float mX;
private float mY;
private boolean mOriginalPressedState;
@Override
public void run() {
if ((mOriginalPressedState == isPressed()) && (mParent != null)
&& mOriginalWindowAttachCount == mWindowAttachCount) {
if (performLongClick(mX, mY)) {
mHasPerformedLongPress = true;
}
}
}
查看MotionEvent.ACTION_MOVE事件，源碼如下:
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;
判斷當(dāng)前坐標(biāo)是否移除了當(dāng)前的view，pointInView(x, y, mTouchSlop)，如果移出，則
- 執(zhí)行removeTapCallback(),移出是滑動容易內(nèi)，則設(shè)置 mPrivateFlags &= ~PFLAG_PREPRESSED且不到100移除回調(diào)
- 執(zhí)行 removeLongPressCallback()，移除長按回調(diào)
- 如果是按壓狀態(tài)，則設(shè)置 mPrivateFlags &= ~PFLAG_PRESSED
總結(jié)：只要用戶移出了我們的控件：則將mPrivateFlags取出PRESSED標(biāo)識，且移除所有在DOWN中設(shè)置的檢測，長按等；
查看MotionEvent.ACTION_UP事件，源碼如下：
case MotionEvent.ACTION_UP:
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
if (!clickable) {
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// take focus if we don't have it already and we should in
// touch mode.
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
if (prepressed) {
// The button is being released before we actually
// showed it as pressed. Make it show the pressed
// state now (before scheduling the click) to ensure
// the user sees it.
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
// 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)) {
performClickInternal();
}
}
}
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;
- 如果mPrivateFlags包含PFLAG_PREPRESSED或者PFLAG_PRESSED則進(jìn)入if執(zhí)行語句,也就是無論100ms內(nèi)或者之后抬起都會進(jìn)入if語句執(zhí)行
- 如果mHasPerformedLongPress是false，即長按沒有執(zhí)行，則進(jìn)入方法體，移除長按回調(diào)
- 如果mPerformClick為null,則初始化一個實(shí)例；然后立即通過Handler添加到消息隊(duì)列尾部，如果添加失敗，直接執(zhí)行performClick()
public boolean performClick() {
// We still need to call this method to handle the cases where performClick() was called
// externally, instead of through performClickInternal()
notifyAutofillManagerOnClick();
final boolean result;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
li.mOnClickListener.onClick(this);
result = true;
} else {
result = false;
}
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
notifyEnterOrExitForAutoFillIfNeeded(true);
return result;
}
- 如果mOnClickListener!=null,則回調(diào)onClick（）方法
- 如果prepressed為true,則執(zhí)行mUnsetPressedState.run()方法。我們的mPrivateFlags中的PRESSED取消，如果mPendingCheckForTap不為null，移除;
總結(jié)
1.整個view的事件分發(fā)流程是：
View.dispatchTouchEvent->View.setOnTouchListener->View.onTouchEvent
在dispatchTouchEvent中會進(jìn)行onTouchListener的判斷，如果不為null且返回ture,則整個事件被消費(fèi)，onTouchEvent不會執(zhí)行，否則執(zhí)行onTouchEvent
- onTouchEvent中的DOWN、MOVE、UP
DOWN時
1、首先設(shè)置mHasPerformedLongPress=false，代表長按是false；
2、如果在滑動容器內(nèi)，首先設(shè)置mPrivateFlags=PFLAG_PREPRESSED且發(fā)送一個延遲100ms的mPendingCheckForTap，則將標(biāo)識位mPrivateFlags=PFLAG_PRESSED，清除PFLAG_PREPRESSED標(biāo)識，同時發(fā)送一個延遲500-100ms的mPendingCheckForLongPress，檢測長按任務(wù)消息
3、如果不在滑動容器內(nèi)容，則直接設(shè)置mPrivateFlags=PFLAG_PRESSED且發(fā)送一個延遲500ms的mPendingCheckForLongPress的檢測長按任務(wù)消息
4、如果時間超過500ms，則觸發(fā)mOnLongClickListener；如果mOnLongClickListener不為null,且mOnLongClickListener.onLongClick返回true,則mHasPerformedLongPress=true;否則mHasPerformedLongPress還是false
MOVE時
主要就是檢測是否劃出了View控件，如果劃出了
直接移除mPendingCheckForTap，mPendingCheckForLongPress；如果100ms后mPrivateFlags==PFLAG_PRESSED，則清除mPrivateFlags值
UP時
- 如果mPrivateFlags=PFLAG_PREPRESSED，即100ms內(nèi)觸發(fā)up,則依次執(zhí)行 setPressed(true, x, y)、mUnsetPressedState
2、如果mHasPerformedLongPress==false，代表長按未觸發(fā)，移除長按檢測，執(zhí)行onClick回調(diào)
3.500ms后，如果設(shè)置了onLongClickListener，且onLongClickListener.onClick返回true，則點(diǎn)擊事件OnClick無法觸發(fā);如果沒有設(shè)置onLongClickListener或者onLongClickListener.onClick返回false,則點(diǎn)擊事件OnClick依舊可以觸發(fā) - 所以onLongClickListener是在move觸發(fā)，onClick是在up觸發(fā)
