View---dispatchTouchEvent
public boolean dispatchTouchEvent(MotionEvent event) {
.......
boolean result = false;
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {//1
result = true;
}
if (!result && onTouchEvent(event)) {//2
result = true;
}
}
......
return result;
}
从2可知，当result为true时，则不会走onTouchEvent(event)，只有result为false时，！result才为true，继续走onTouchEvent(event)。那继续分析1处的四个条件。
先来看mListenerInfo什么时候赋值？
public void setOnTouchListener(OnTouchListener l) {
getListenerInfo().mOnTouchListener = l;
}
ListenerInfo getListenerInfo() {
if (mListenerInfo != null) {
return mListenerInfo;
}
mListenerInfo = new ListenerInfo();
return mListenerInfo;
}
从setOnTouchListener可知，当我们设置OnTouchListener事件的时候，mListenerInfo就会初始化，并且把mOnTouchListener进行赋值。
所以只要我们设置setOnTouchListener，li != null && li.mOnTouchListener != null就成立。第三个条件为使能条件，既然能设置监听事件，肯定为true.
li.mOnTouchListener.onTouch(this, event)则是onTouch的回调，如果返回true，则result = true,当result = true，则2处的onTouchEvent（）则不会走。
反之，则onTouchEvent会走。所以OnTouchListener优先于onTouchEvent（）执行。
看了一圈，都没有看到关于onClick(),所以猜测onClick()在onTouchEvent()中。
View ----- onTouchEvent（）
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
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;
return clickable;
}
if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
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) {
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
if (prepressed) {
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
if (!focusTaken) {
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;
case MotionEvent.ACTION_DOWN:
mHasPerformedLongPress = false;
if (!clickable) {
checkForLongClick(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
break;
}
if (performButtonActionOnTouchDown(event)) {
break;
}
boolean isInScrollingContainer = isInScrollingContainer();
if (isInScrollingContainer) {
mPrivateFlags |= PFLAG_PREPRESSED;
if (mPendingCheckForTap == null) {
mPendingCheckForTap = new CheckForTap();
}
mPendingCheckForTap.x = event.getX();
mPendingCheckForTap.y = event.getY();
postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
} else {
setPressed(true, x, y);
checkForLongClick(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
break;
case MotionEvent.ACTION_MOVE:
// 判断当前的坐标是否在点击的按钮内部
// 如果不在按钮内部则移除长按事件，如果pressed==true则将pressed设置为false，意味着不响应点击事件
if (!pointInView(x, y, mTouchSlop)) {
removeLongPressCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
}
break;
......
return true;
}
return false;
}
我们可以看到在ACTION_UP中会调用performClickInternal()，该方法就是调用onClick事件。
private boolean performClickInternal() {
notifyAutofillManagerOnClick();
return performClick();
}
public boolean performClick() {
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;
}
return result;
}
当我们设置了onClickListener的时候，就会调用onClick事件。反之不会。
观察到onClick返回值为void，这样做的目的表示该事件被消费了。
给一个button同时设置onClickListener和onLongClickListener，长按这个button，长按跟单击事件是否都能够得到响应？
首先我们是button，clickable默认是true，手指点下的时候，会走ACTION_DOWN事件。
case MotionEvent.ACTION_DOWN:
if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {
mPrivateFlags3 |= PFLAG3_FINGER_DOWN;
}
mHasPerformedLongPress = false;
if (!clickable) {
checkForLongClick(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
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(
ViewConfiguration.getLongPressTimeout(),
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
break;
因为clickable为 true，所以第一个if不会进去；isInScrollingContainer表示是否在一个滚动的容器中。
布局中就一个button，显然不在滚动的容器中，所以会走else代码。
在down中设置pressed状态为true，然后发送一个延迟500毫秒的事件去执行长按事件。
private void checkForLongClick(long delay, float x, float y, int classification) {
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();
mPendingCheckForLongPress.setClassification(classification);
postDelayed(mPendingCheckForLongPress, delay);
}
}
private final class CheckForLongPress implements Runnable {
private int mOriginalWindowAttachCount;
private float mX;
private float mY;
private boolean mOriginalPressedState;
/**
* The classification of the long click being checked: one of the
* StatsLog.TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__* constants.
*/
private int mClassification;
@Override
public void run() {
if ((mOriginalPressedState == isPressed()) && (mParent != null)
&& mOriginalWindowAttachCount == mWindowAttachCount) {
recordGestureClassification(mClassification);
if (performLongClick(mX, mY)) {
mHasPerformedLongPress = true;
}
}
}
}
执行了onLongClick事件之后，将mHasPerformedLongPress设置为true。
然后回到ACTION_UP
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) {
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
focusTaken = requestFocus();
}
if (prepressed) {
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) {
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;
因为在ACTION_DOWN中把mHasPerformedLongPress设置为true，所以就不会去执行performClickInternal()，也就是不会去执行onClick()。
button同时设置onClickListener和onLongClickListener，长按这个button，最终只能长按事件得到响应。
界面上有两个button，点击一个按钮，然后滑到第二个按钮抬起，如果这两个按钮都设置了点击事件，会不会触发？
由于滑动，所以会走ACTION_MOVE事件。
case MotionEvent.ACTION_MOVE:
// Be lenient about moving outside of buttons
if (!pointInView(x, y, touchSlop)) {
removeTapCallback();
removeLongPressCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
}
......
break;
当手指滑动的时候，在move事件中时刻监听当然手指所在的坐标点，如果当前坐标不在按钮内部，那么就移除长按事件，并且设置pressed=false。
点击第一个按钮，然后滑动到第二个按钮后抬起，第一个按钮会执行一个完整的事件序列（down->move->up），由于这move的过程中pressed设置为false了，所以不会响应点击事件，如果在500毫秒之内移出了第一个按钮长按事件也不会响应。第二个按钮由于没有获取到down事件，同一个事件序列不会交给它处理，意味着不会执行move以及up事件，所以第二个按钮不会响应点击事件。