事件类型
-
安卓事件类型
事件一般是从ACTION_DOWN开始处理的
view的继承关系
view的继承关系
viewGroup负责分发事件,处理事件最终要调用view的函数处理
事件处理过程
因为事件处理过程较为简单我们先结合源码分析处理过程
提示：因为源码部分很多，所以不想看源码的同学可以直接跳到底部的总结部分
按钮点击事件处理分析
在一个简单页面中设置一个按钮设置click监听器和touch监听器并且重写里面的方法
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout1);
Button button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.i("info","onclick");
}
});
button.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.i("info","ontouch"+i);
i++;
return true;
}
});
}
点击按钮Log如下
log1
显然onclick没有执行
接下来改写代码将ontuch中return true改写成return false
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout1);
Button button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.i("info","onclick");
}
});
button.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.i("info","ontouch"+i);
i++;
return false;
}
});
}
再次点击按钮log如下
log2
现在onclick已经执行并且是在两次ontouch之后
接下来让我们深入源码看看这是怎么回事
因为我们现在分析执行事件部分因此先忽略事件分发的部分
直接看View的 部分源码dispatchTouchEvent
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)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//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;
}
boolean isAccessibilityFocusedViewOrHost() {
return isAccessibilityFocused() || (getViewRootImpl() != null && getViewRootImpl()
.getAccessibilityFocusedHost() == this);
}
这部分源码最重要的部分在于
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;
}
上面第一个if判断语句中前3个条件一般都是true
关键在于li.mOnTouchListener.onTouch(this, event)
是不是觉得这个函数挺熟悉?
这就是我们之前在button中重写的函数之一
- 第一种情况下让onTouch返回true
这种情况下
第一个if为真,所以result被赋值为true
因为第二个if中使用的是连接词为&&所以!result为false不会执行后面的onTouchEvent() 也就没有后序了
而我刚刚操作的点击事件就点击了一下，没有进行移动所以只会产生DOWN和UP两个事件
因此对应的log就显示输出了两次ontouch没有onclick。 - 第二种情况下让onTouch返回false
根据上面的分析这次onTouchEvent()将会执行
接下来让我们看看onTouchEvent()的源码
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;
// 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:
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;
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;
case MotionEvent.ACTION_CANCEL:
if (clickable) {
setPressed(false);
}
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
break;
case MotionEvent.ACTION_MOVE:
if (clickable) {
drawableHotspotChanged(x, y);
}
final int motionClassification = event.getClassification();
final boolean ambiguousGesture =
motionClassification == MotionEvent.CLASSIFICATION_AMBIGUOUS_GESTURE;
int touchSlop = mTouchSlop;
if (ambiguousGesture && hasPendingLongPressCallback()) {
if (!pointInView(x, y, touchSlop)) {
// The default action here is to cancel long press. But instead, we
// just extend the timeout here, in case the classification
// stays ambiguous.
removeLongPressCallback();
long delay = (long) (ViewConfiguration.getLongPressTimeout()
* mAmbiguousGestureMultiplier);
// Subtract the time already spent
delay -= event.getEventTime() - event.getDownTime();
checkForLongClick(
delay,
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__LONG_PRESS);
}
touchSlop *= mAmbiguousGestureMultiplier;
}
// Be lenient about moving outside of buttons
if (!pointInView(x, y, touchSlop)) {
// Outside button
// Remove any future long press/tap checks
removeTapCallback();
removeLongPressCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
}
final boolean deepPress =
motionClassification == MotionEvent.CLASSIFICATION_DEEP_PRESS;
if (deepPress && hasPendingLongPressCallback()) {
// process the long click action immediately
removeLongPressCallback();
checkForLongClick(
0 /* send immediately */,
x,
y,
TOUCH_GESTURE_CLASSIFIED__CLASSIFICATION__DEEP_PRESS);
}
break;
}
return true;
}
return false;
}
可以看见这个源码非常的长 ,不过我们要注意的部分主要只有四个部分就是分别对应四个事件的DOWN ,UP , MOVE ,CANCLE
而我们点击按钮只涉及到DOWN和UP
其中DOWN里面处理的内容与我们这次实验无关
所以我们将UP部分代码提出来看看
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;
上面代码中最重要的是
调用 performClickInternal()
private boolean performClickInternal() {
// Must notify autofill manager before performing the click actions to avoid scenarios where
// the app has a click listener that changes the state of views the autofill service might
// be interested on.
notifyAutofillManagerOnClick();
return performClick();
}
函数返回了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;
}
是不是又觉得上面的代码很熟悉
没错它跟onTouch()是一个书写风格
在这里我们们调用了li.mOnClickListener.onClick(this)也就是我们在按钮中重写的函数
至此第二中情况也就分析完了
出现两次ontouch然后接一个onclick
总结
处理点击事件时
- View.dispatchTouchEvent()
- mOnTouchListener.onTouch(this,event)
- 根据result看是否调用View.onTouchEvent
- 假设继续调用View.onTouchEvent
- 调用UP部分的performClickInternal()
- 调用performClick()
- 最终调用我们重写的click()
抽象出来处理事件时
- View.dispatchTouchEvent()
- mOnTouchListener.onTouch(this,event)
- 根据result看是否调用View.onTouchEvent
- 调用View.onTouchEvent 根据不同事件进行不同的处理