事件分发的源码解析
2016-12-28 17:14
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经过上一节的讲解，我们本节从Android源码来分析
1、activity对点击事件的分发过程
点击事件有motionevent来表示，当一个点击操作发生时，事件最先传递给当前的activity，有activity的dispatchTouchevent来进行事件分发，具体的工作由activity的内部window来完成，window会将事件传递给decor view，decorview一般就是当前界面的底层容器（即setcontetview所设置view的父容器），通过Activity.getwindow.decorview()来获得。我们先从activity的dispatchTouchevent来分析：
/**
* Called to process touch screen events. You can override this to
* intercept all touch screen events before they are dispatched to the
* window. Be sure to call this implem2、entation for touch screen events
* that should be handled normally.
*
* @param ev The touch screen event.
*
* @return boolean Return true if this event was consumed.
*/
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
activity先把事件交给window进行分发，如果返回true，那就说明事件已经被处理了，整个事件循环就结束了。如果返回false，那么说明事件没有被处理，所有的view的ontouchevent返回都为false，事件将要交给activity的ontouchevent来处理。
接下来，我们看看window是如何传递给viewgroup的.通过源码我们知道window是个抽象类，superDispatchTouchEvent是个抽象方法，因此我们必须找到window的实现类才行，他的唯一实现类是phonewindow 这个可以从window类中看出来：
/**
* Abstract base class for a top-level window look and behavior policy. An
* instance of this class should be used as the top-level view added to the
* window manager. It provides standard UI policies such as a background, title
* area, default key processing, etc.
*
* <p>The only existing implementation of this abstract class is
* android.view.PhoneWindow, which you should instantiate when needing a
* Window.
*/
public abstract class Window {
他的大概意思是window可以控制顶级view的外观和行为策略，他的唯一实现位于Android.policy.phoneWindow这个类。尽管实列化的时候此类会被重构，但仅是重构而已，功能是类似的，他处理点击事件如下所示
public boolean superDispatchTouchEvent(MotionEvent event){
return mdecor.superDispatchTouchEvent(event);
};
这里可以看清楚我们的phonewindow把点击事件传递给decorview ，我们来看看decorview是什么呢？
1. PhoneWindow根据Manifest的主题或者是特定的PhoneWindow设置去生成一个DevorView的布局，作为跟视图(Root View)。
2. Activity调用setContentView()方法把用户自定义的Layout XML文件作为内容视图(Content View), 当然其内部是调用PhoneWindow的setContentView()方法。
3. 经过上两步，UI视图就已经形成了，那么当UI每次被刷新的时候，View Tree就会像上面所说的那样被Traverse。
到这里我们的事件传递到顶级view了，即在activity中通过setcntentview 设置的view了，另外顶级view又叫做根view，顶级view一般都是viewgroup；下面我们来看看顶级view对点击事件 的分发过程。
2、顶级view对事件的分发过程解析
关于事件如何在顶级view中分发，我们上一篇文章已经讲过了，这里来回忆一下；当点击事件到达顶级view也就是viewgroup之后，会触发view的dispatchTouchEvent方法之后的逻辑是这样的：如果顶级viewgroup拦截事件即onintercepttouchevent方法返回true；则事件有viewgroup处理，如果viewgroup的montouchlistener被设置，则ontouch方法会被调用，否则ontouchevent会被调用，如果顶级viewgroup不拦截事件，则事件会传递给他所在点击事件上的子view，这时子view上的dispatchtouchevent方法会被调用，这是顶级view的事件传递给子view，接下来的传递过程和顶级view的传递过程一致。
首先来看看viewgroup对点击事件的分发过程，主要实现在dispatchtouchevent的方法中，但这个方法比较长，我们分段分析，先看看下边的他描述的是view是否拦截当前点击事件的逻辑
// Check for interception.
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
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;
}
从上边的代码我们可以看出来，viewgroup有两种情况会判断是否拦截当前事件：事件类型为actiondown或者mfirsttouchtarget！=null；actiondown好理解，但是mfirsttouchtarget！=null又该怎么理解呢？这个从后面的代码逻辑可以看出来，当事件由viewgroup的子元素成功处理时，mfirsttouchtarget会被赋值并指向子元素，换个方式来说，当viewgroup不拦截事件，并将事件交由子元素处理时mfirsttouchtarget！=null，反过来一旦事件被当前viewgroup拦截时，mfirsttouchtarget！=null就不成立，那么当actionmove和actionup事件到来时，由于actionMasked
== MotionEvent.ACTION_DOWN || mFirstTouchTarget != null这个条件为false，那么将导致viewgroup的onInterceptTouchEvent不会再被调用，并且同一事件中的其他事件都会默认交给他来处理。
当然这里有一个特殊情况，就是FLAG_DISALLOW_INTERCEPT标记为，这个标记为是通过requestdisallowintercepttouchevent来设置，一般用于子view中，FLAG_DISALLOW_INTERCEPT一旦设置后，viewgroup将没有办法拦截除了actiondown以外的其他事件，因为当viewgroup在处理分发事件时，如果是actiondown时就会重置FLAG_DISALLOW_INTERCEPT标记为，导致子view中设置这个标记为是无效的。当面对actiondown时viewgroup总会调用自己的onintercepttouchevent方法来询问自己是否要拦截事件。在下面的代码中，当actiondown事件到来时，做重置状态的操作，而在tresttouchstate方法中会对FLAG_DISALLOW_INTERCEPT进行重置，因此子view调用
requestdisallowintercepttouchevent并不影响子viewgroup对actiondown的处理。
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {
// 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.
cancelAndClearTouchTargets(ev);
resetTouchState();
}
从上边的分析，我们得出结论，当viewgroup决定拦截事件后，其他的事件都将会交由他来处理，不再调用onintercepttouchevent方法，FLAG_DISALLOW_INTERCEPT标志位是让viewgroup不再拦截actiondown事件，总结得到以下几点（1）、onintercepttouchevent不是每次都会被调用的，如果我们想提前处理所有的点击事件，要选择dispatchtouchevent方法，只有这个方法每次都会被调用。另外一点FLAG_DISALLOW_INTERCEPT标记为给我们提供另外一种思路，当面对滑动冲突时可以考虑用此方法来解决。
3、view对点击事件的处理过程
view对点击事件的过程要稍微简单，注意这里的view不包含viewgroup，首先看他的dispatchtouchevent方法：
/**
* Pass the touch screen motion event down to the target view, or this
* view if it is the target.
*
* @param event The motion event to be dispatched.
* @return True if the event was handled by the view, false otherwise.
*/
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) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
if (!result && onTouchEvent(event)) {
result = true;
}
}
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.
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
因为view是一个单独的元素，他没有子元素，所以没办法向下传递事件，所以他要自己处理事件，从上面的源码可以看出来view对点击事件的处理过程，首先会判断有没有ontouchlistener，如果ontouchlistener中的ontouch返回true，那么ontouchevent将不会被调用，可见ontouchlistener的优先级高于ontouchevent，这样做的好处是方便外界处理点击事件。接着在分析ontouchevent的实现先看view处于不可用状态下点击事件的处理过程，由此可以看出不可用状态下view的点击事件还是会被消耗，尽管他看起来不可用。
if ((viewFlags & ENABLED_MASK) == DISABLED) {
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.
return (((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
}
下边来看看view对点击事件的处理
if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
(viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {
switch (action) {
case MotionEvent.ACTION_UP:
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)) {
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:
mHasPerformedLongPress = false;
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);
}
break;
case MotionEvent.ACTION_CANCEL:
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
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
removeTapCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
// Remove any future long press/tap checks
removeLongPressCallback();
setPressed(false);
}
}
break;
}
return true;
}
从上面的代码可以看出来，只要view的clickable和longclickable其中一个为true那么事件就会被消耗掉，当actionup事件发生时，会触发performclick方法，如果view设置了onclicklistener，那么performclick中会调用conclick方法。如下所示
public boolean performClick() {
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);
return result;
}
1、activity对点击事件的分发过程
点击事件有motionevent来表示，当一个点击操作发生时，事件最先传递给当前的activity，有activity的dispatchTouchevent来进行事件分发，具体的工作由activity的内部window来完成，window会将事件传递给decor view，decorview一般就是当前界面的底层容器（即setcontetview所设置view的父容器），通过Activity.getwindow.decorview()来获得。我们先从activity的dispatchTouchevent来分析：
/**
* Called to process touch screen events. You can override this to
* intercept all touch screen events before they are dispatched to the
* window. Be sure to call this implem2、entation for touch screen events
* that should be handled normally.
*
* @param ev The touch screen event.
*
* @return boolean Return true if this event was consumed.
*/
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}
activity先把事件交给window进行分发，如果返回true，那就说明事件已经被处理了，整个事件循环就结束了。如果返回false，那么说明事件没有被处理，所有的view的ontouchevent返回都为false，事件将要交给activity的ontouchevent来处理。
接下来，我们看看window是如何传递给viewgroup的.通过源码我们知道window是个抽象类，superDispatchTouchEvent是个抽象方法，因此我们必须找到window的实现类才行，他的唯一实现类是phonewindow 这个可以从window类中看出来：
/**
* Abstract base class for a top-level window look and behavior policy. An
* instance of this class should be used as the top-level view added to the
* window manager. It provides standard UI policies such as a background, title
* area, default key processing, etc.
*
* <p>The only existing implementation of this abstract class is
* android.view.PhoneWindow, which you should instantiate when needing a
* Window.
*/
public abstract class Window {
他的大概意思是window可以控制顶级view的外观和行为策略，他的唯一实现位于Android.policy.phoneWindow这个类。尽管实列化的时候此类会被重构，但仅是重构而已，功能是类似的，他处理点击事件如下所示
public boolean superDispatchTouchEvent(MotionEvent event){
return mdecor.superDispatchTouchEvent(event);
};
这里可以看清楚我们的phonewindow把点击事件传递给decorview ，我们来看看decorview是什么呢？
private final class DecorView extends FrameLayout implements RootViewSurfaceTaker {}1. PhoneWindow根据Manifest的主题或者是特定的PhoneWindow设置去生成一个DevorView的布局，作为跟视图(Root View)。
2. Activity调用setContentView()方法把用户自定义的Layout XML文件作为内容视图(Content View), 当然其内部是调用PhoneWindow的setContentView()方法。
3. 经过上两步，UI视图就已经形成了，那么当UI每次被刷新的时候，View Tree就会像上面所说的那样被Traverse。
到这里我们的事件传递到顶级view了，即在activity中通过setcntentview 设置的view了，另外顶级view又叫做根view，顶级view一般都是viewgroup；下面我们来看看顶级view对点击事件 的分发过程。
2、顶级view对事件的分发过程解析
关于事件如何在顶级view中分发，我们上一篇文章已经讲过了，这里来回忆一下；当点击事件到达顶级view也就是viewgroup之后，会触发view的dispatchTouchEvent方法之后的逻辑是这样的：如果顶级viewgroup拦截事件即onintercepttouchevent方法返回true；则事件有viewgroup处理，如果viewgroup的montouchlistener被设置，则ontouch方法会被调用，否则ontouchevent会被调用，如果顶级viewgroup不拦截事件，则事件会传递给他所在点击事件上的子view，这时子view上的dispatchtouchevent方法会被调用，这是顶级view的事件传递给子view，接下来的传递过程和顶级view的传递过程一致。
首先来看看viewgroup对点击事件的分发过程，主要实现在dispatchtouchevent的方法中，但这个方法比较长，我们分段分析，先看看下边的他描述的是view是否拦截当前点击事件的逻辑
// Check for interception.
final boolean intercepted;
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
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;
}
从上边的代码我们可以看出来，viewgroup有两种情况会判断是否拦截当前事件：事件类型为actiondown或者mfirsttouchtarget！=null；actiondown好理解，但是mfirsttouchtarget！=null又该怎么理解呢？这个从后面的代码逻辑可以看出来，当事件由viewgroup的子元素成功处理时，mfirsttouchtarget会被赋值并指向子元素，换个方式来说，当viewgroup不拦截事件，并将事件交由子元素处理时mfirsttouchtarget！=null，反过来一旦事件被当前viewgroup拦截时，mfirsttouchtarget！=null就不成立，那么当actionmove和actionup事件到来时，由于actionMasked
== MotionEvent.ACTION_DOWN || mFirstTouchTarget != null这个条件为false，那么将导致viewgroup的onInterceptTouchEvent不会再被调用，并且同一事件中的其他事件都会默认交给他来处理。
当然这里有一个特殊情况，就是FLAG_DISALLOW_INTERCEPT标记为，这个标记为是通过requestdisallowintercepttouchevent来设置，一般用于子view中，FLAG_DISALLOW_INTERCEPT一旦设置后，viewgroup将没有办法拦截除了actiondown以外的其他事件，因为当viewgroup在处理分发事件时，如果是actiondown时就会重置FLAG_DISALLOW_INTERCEPT标记为，导致子view中设置这个标记为是无效的。当面对actiondown时viewgroup总会调用自己的onintercepttouchevent方法来询问自己是否要拦截事件。在下面的代码中，当actiondown事件到来时，做重置状态的操作，而在tresttouchstate方法中会对FLAG_DISALLOW_INTERCEPT进行重置，因此子view调用
requestdisallowintercepttouchevent并不影响子viewgroup对actiondown的处理。
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {
// 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.
cancelAndClearTouchTargets(ev);
resetTouchState();
}
从上边的分析，我们得出结论，当viewgroup决定拦截事件后，其他的事件都将会交由他来处理，不再调用onintercepttouchevent方法，FLAG_DISALLOW_INTERCEPT标志位是让viewgroup不再拦截actiondown事件，总结得到以下几点（1）、onintercepttouchevent不是每次都会被调用的，如果我们想提前处理所有的点击事件，要选择dispatchtouchevent方法，只有这个方法每次都会被调用。另外一点FLAG_DISALLOW_INTERCEPT标记为给我们提供另外一种思路，当面对滑动冲突时可以考虑用此方法来解决。
3、view对点击事件的处理过程
view对点击事件的过程要稍微简单，注意这里的view不包含viewgroup，首先看他的dispatchtouchevent方法：
/**
* Pass the touch screen motion event down to the target view, or this
* view if it is the target.
*
* @param event The motion event to be dispatched.
* @return True if the event was handled by the view, false otherwise.
*/
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) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
if (!result && onTouchEvent(event)) {
result = true;
}
}
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.
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
因为view是一个单独的元素，他没有子元素，所以没办法向下传递事件，所以他要自己处理事件，从上面的源码可以看出来view对点击事件的处理过程，首先会判断有没有ontouchlistener，如果ontouchlistener中的ontouch返回true，那么ontouchevent将不会被调用，可见ontouchlistener的优先级高于ontouchevent，这样做的好处是方便外界处理点击事件。接着在分析ontouchevent的实现先看view处于不可用状态下点击事件的处理过程，由此可以看出不可用状态下view的点击事件还是会被消耗，尽管他看起来不可用。
if ((viewFlags & ENABLED_MASK) == DISABLED) {
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.
return (((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
}
下边来看看view对点击事件的处理
if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
(viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {
switch (action) {
case MotionEvent.ACTION_UP:
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)) {
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:
mHasPerformedLongPress = false;
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);
}
break;
case MotionEvent.ACTION_CANCEL:
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
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
removeTapCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
// Remove any future long press/tap checks
removeLongPressCallback();
setPressed(false);
}
}
break;
}
return true;
}
从上面的代码可以看出来，只要view的clickable和longclickable其中一个为true那么事件就会被消耗掉，当actionup事件发生时，会触发performclick方法，如果view设置了onclicklistener，那么performclick中会调用conclick方法。如下所示
public boolean performClick() {
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);
return result;
}
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