Android(安卓)View 事件分发机制 源码解析
1、案例
为了更好的研究View的事件转发,我们自定以一个MyButton继承Button,然后把跟事件传播有关的方法进行复写,然后添加上日志~
MyButton
[java] view plain copy
- packagecom.example.zhy_event03;
- importandroid.content.Context;
- importandroid.util.AttributeSet;
- importandroid.util.Log;
- importandroid.view.MotionEvent;
- importandroid.widget.Button;
- publicclassMyButtonextendsButton
- {
- privatestaticfinalStringTAG=MyButton.class.getSimpleName();
- publicMyButton(Contextcontext,AttributeSetattrs)
- {
- super(context,attrs);
- }
- @Override
- publicbooleanonTouchEvent(MotionEventevent)
- {
- intaction=event.getAction();
- switch(action)
- {
- caseMotionEvent.ACTION_DOWN:
- Log.e(TAG,"onTouchEventACTION_DOWN");
- break;
- caseMotionEvent.ACTION_MOVE:
- Log.e(TAG,"onTouchEventACTION_MOVE");
- break;
- caseMotionEvent.ACTION_UP:
- Log.e(TAG,"onTouchEventACTION_UP");
- break;
- default:
- break;
- }
- returnsuper.onTouchEvent(event);
- }
- @Override
- publicbooleandispatchTouchEvent(MotionEventevent)
- {
- intaction=event.getAction();
- switch(action)
- {
- caseMotionEvent.ACTION_DOWN:
- Log.e(TAG,"dispatchTouchEventACTION_DOWN");
- break;
- caseMotionEvent.ACTION_MOVE:
- Log.e(TAG,"dispatchTouchEventACTION_MOVE");
- break;
- caseMotionEvent.ACTION_UP:
- Log.e(TAG,"dispatchTouchEventACTION_UP");
- break;
- default:
- break;
- }
- returnsuper.dispatchTouchEvent(event);
- }
- }
在onTouchEvent和dispatchTouchEvent中打印了日志~
然后把我们自定义的按钮加到主布局文件中;
布局文件:
[html] view plain copy
- <LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
- xmlns:tools="http://schemas.android.com/tools"
- android:layout_width="match_parent"
- android:layout_height="match_parent"
- tools:context=".MainActivity">
- <com.example.zhy_event03.MyButton
- android:id="@+id/id_btn"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:text="clickme"/>
- </LinearLayout>
最后看一眼MainActivity的代码
[java] view plain copy
- packagecom.example.zhy_event03;
- importandroid.app.Activity;
- importandroid.os.Bundle;
- importandroid.util.Log;
- importandroid.view.MotionEvent;
- importandroid.view.View;
- importandroid.view.View.OnTouchListener;
- importandroid.widget.Button;
- publicclassMainActivityextendsActivity
- {
- protectedstaticfinalStringTAG="MyButton";
- privateButtonmButton;
- @Override
- protectedvoidonCreate(BundlesavedInstanceState)
- {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
- mButton=(Button)findViewById(R.id.id_btn);
- mButton.setOnTouchListener(newOnTouchListener()
- {
- @Override
- publicbooleanonTouch(Viewv,MotionEventevent)
- {
- intaction=event.getAction();
- switch(action)
- {
- caseMotionEvent.ACTION_DOWN:
- Log.e(TAG,"onTouchACTION_DOWN");
- break;
- caseMotionEvent.ACTION_MOVE:
- Log.e(TAG,"onTouchACTION_MOVE");
- break;
- caseMotionEvent.ACTION_UP:
- Log.e(TAG,"onTouchACTION_UP");
- break;
- default:
- break;
- }
- returnfalse;
- }
- });
- }
- }
在MainActivity中,我们还给MyButton设置了OnTouchListener这个监听~
好了,跟View事件相关一般就这三个地方了,一个onTouchEvent,一个dispatchTouchEvent,一个setOnTouchListener;
下面我们运行,然后点击按钮,查看日志输出:
[html] view plain copy
- 08-3106:09:39.030:E/MyButton(879):dispatchTouchEventACTION_DOWN
- 08-3106:09:39.030:E/MyButton(879):onTouchACTION_DOWN
- 08-3106:09:39.049:E/MyButton(879):onTouchEventACTION_DOWN
- 08-3106:09:39.138:E/MyButton(879):dispatchTouchEventACTION_MOVE
- 08-3106:09:39.138:E/MyButton(879):onTouchACTION_MOVE
- 08-3106:09:39.147:E/MyButton(879):onTouchEventACTION_MOVE
- 08-3106:09:39.232:E/MyButton(879):dispatchTouchEventACTION_UP
- 08-3106:09:39.248:E/MyButton(879):onTouchACTION_UP
- 08-3106:09:39.248:E/MyButton(879):onTouchEventACTION_UP
我有意点击的时候蹭了一下,不然不会触发MOVE,手抖可能会打印一堆MOVE的日志~~~
好了,可以看到,不管是DOWN,MOVE,UP都会按照下面的顺序执行:
1、dispatchTouchEvent
2、setOnTouchListener的onTouch
3、onTouchEvent
下面就跟随日志的脚步开始源码的探索~
2、dispatchTouchEvent
首先进入View的dispatchTouchEvent
[java] view plain copy
- /**
- *Passthetouchscreenmotioneventdowntothetargetview,orthis
- *viewifitisthetarget.
- *
- *@parameventThemotioneventtobedispatched.
- *@returnTrueiftheeventwashandledbytheview,falseotherwise.
- */
- publicbooleandispatchTouchEvent(MotionEventevent){
- if(!onFilterTouchEventForSecurity(event)){
- returnfalse;
- }
- if(mOnTouchListener!=null&&(mViewFlags&ENABLED_MASK)==ENABLED&&
- mOnTouchListener.onTouch(this,event)){
- returntrue;
- }
- returnonTouchEvent(event);
- }
直接看13行:首先判断mOnTouchListener不为null,并且view是enable的状态,然后mOnTouchListener.onTouch(this, event)返回true,这三个条件如果都满足,直接return true ; 也就是下面的onTouchEvent(event)不会被执行了;
那么mOnTouchListener是和方神圣,我们来看看:
[java] view plain copy
- /**
- *Registeracallbacktobeinvokedwhenatoucheventissenttothisview.
- *@paramlthetouchlistenertoattachtothisview
- */
- publicvoidsetOnTouchListener(OnTouchListenerl){
- mOnTouchListener=l;
- }
也就是说:如果我们设置了setOnTouchListener,并且return true,那么View自己的onTouchEvent就不会被执行了,当然了,本例我们return false,我们还得往下探索 ;
已经解决一个常见的问题:View的onTouchListener和onTouchEvent的调用关系,相信大家应该已经明白了~let's go;继续往下。
3、View的onTouchEvent:
接下来是View的onTouchEvent:
[java] view plain copy
- /**
- *Implementthismethodtohandletouchscreenmotionevents.
- *
- *@parameventThemotionevent.
- *@returnTrueiftheeventwashandled,falseotherwise.
- */
- publicbooleanonTouchEvent(MotionEventevent){
- finalintviewFlags=mViewFlags;
- if((viewFlags&ENABLED_MASK)==DISABLED){
- //Adisabledviewthatisclickablestillconsumesthetouch
- //events,itjustdoesn'trespondtothem.
- return(((viewFlags&CLICKABLE)==CLICKABLE||
- (viewFlags&LONG_CLICKABLE)==LONG_CLICKABLE));
- }
- if(mTouchDelegate!=null){
- if(mTouchDelegate.onTouchEvent(event)){
- returntrue;
- }
- }
- if(((viewFlags&CLICKABLE)==CLICKABLE||
- (viewFlags&LONG_CLICKABLE)==LONG_CLICKABLE)){
- switch(event.getAction()){
- caseMotionEvent.ACTION_UP:
- booleanprepressed=(mPrivateFlags&PREPRESSED)!=0;
- if((mPrivateFlags&PRESSED)!=0||prepressed){
- //takefocusifwedon'thaveitalreadyandweshouldin
- //touchmode.
- booleanfocusTaken=false;
- if(isFocusable()&&isFocusableInTouchMode()&&!isFocused()){
- focusTaken=requestFocus();
- }
- if(!mHasPerformedLongPress){
- //Thisisatap,soremovethelongpresscheck
- removeLongPressCallback();
- //Onlyperformtakeclickactionsifwewereinthepressedstate
- if(!focusTaken){
- //UseaRunnableandpostthisratherthancalling
- //performClickdirectly.Thisletsothervisualstate
- //oftheviewupdatebeforeclickactionsstart.
- if(mPerformClick==null){
- mPerformClick=newPerformClick();
- }
- if(!post(mPerformClick)){
- performClick();
- }
- }
- }
- if(mUnsetPressedState==null){
- mUnsetPressedState=newUnsetPressedState();
- }
- if(prepressed){
- mPrivateFlags|=PRESSED;
- refreshDrawableState();
- postDelayed(mUnsetPressedState,
- ViewConfiguration.getPressedStateDuration());
- }elseif(!post(mUnsetPressedState)){
- //Ifthepostfailed,unpressrightnow
- mUnsetPressedState.run();
- }
- removeTapCallback();
- }
- break;
- caseMotionEvent.ACTION_DOWN:
- if(mPendingCheckForTap==null){
- mPendingCheckForTap=newCheckForTap();
- }
- mPrivateFlags|=PREPRESSED;
- mHasPerformedLongPress=false;
- postDelayed(mPendingCheckForTap,ViewConfiguration.getTapTimeout());
- break;
- caseMotionEvent.ACTION_CANCEL:
- mPrivateFlags&=~PRESSED;
- refreshDrawableState();
- removeTapCallback();
- break;
- caseMotionEvent.ACTION_MOVE:
- finalintx=(int)event.getX();
- finalinty=(int)event.getY();
- //Belenientaboutmovingoutsideofbuttons
- intslop=mTouchSlop;
- if((x<0-slop)||(x>=getWidth()+slop)||
- (y<0-slop)||(y>=getHeight()+slop)){
- //Outsidebutton
- removeTapCallback();
- if((mPrivateFlags&PRESSED)!=0){
- //Removeanyfuturelongpress/tapchecks
- removeLongPressCallback();
- //Needtoswitchfrompressedtonotpressed
- mPrivateFlags&=~PRESSED;
- refreshDrawableState();
- }
- }
- break;
- }
- returntrue;
- }
- returnfalse;
- }
代码还是比较长的,
10-15行,如果当前View是Disabled状态且是可点击则会消费掉事件(return true);可以忽略,不是我们的重点;17-21行,如果设置了mTouchDelegate,则会将事件交给代理者处理,直接return true,如果大家希望自己的View增加它的touch范围,可以尝试使用TouchDelegate,这里也不是重点,可以忽略;
接下来到我们的重点了:
23行的判断:如果我们的View可以点击或者可以长按,则,注意IF的范围,最终一定return true ;
if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)) {
//...
return true;
}
接下来就是 switch (event.getAction())了,判断事件类型,DOWN,MOVE,UP等;
我们按照例子执行的顺序,先看 case MotionEvent.ACTION_DOWN (71-78行):
1、MotionEvent.ACTION_DOWN
75行:给mPrivateFlags设置一个PREPRESSED的标识
76行:设置mHasPerformedLongPress=false;表示长按事件还未触发;
77行:发送一个延迟为ViewConfiguration.getTapTimeout()的延迟消息,到达延时时间后会执行CheckForTap()里面的run方法:
1、ViewConfiguration.getTapTimeout()为115毫秒;
2、CheckForTap
[java] view plain copy
- privatefinalclassCheckForTapimplementsRunnable{
- publicvoidrun(){
- mPrivateFlags&=~PREPRESSED;
- mPrivateFlags|=PRESSED;
- refreshDrawableState();
- if((mViewFlags&LONG_CLICKABLE)==LONG_CLICKABLE){
- postCheckForLongClick(ViewConfiguration.getTapTimeout());
- }
- }
- }
在run方法里面取消mPrivateFlags的PREPRESSED,然后设置PRESSED标识,刷新背景,如果View支持长按事件,则再发一个延时消息,检测长按;
[java] view plain copy
- privatevoidpostCheckForLongClick(intdelayOffset){
- mHasPerformedLongPress=false;
- if(mPendingCheckForLongPress==null){
- mPendingCheckForLongPress=newCheckForLongPress();
- }
- mPendingCheckForLongPress.rememberWindowAttachCount();
- postDelayed(mPendingCheckForLongPress,
- ViewConfiguration.getLongPressTimeout()-delayOffset);
- }
[java] view plain copy
- classCheckForLongPressimplementsRunnable{
- privateintmOriginalWindowAttachCount;
- publicvoidrun(){
- if(isPressed()&&(mParent!=null)
- &&mOriginalWindowAttachCount==mWindowAttachCount){
- if(performLongClick()){
- mHasPerformedLongPress=true;
- }
- }
- }
可以看到,当用户按下,首先会设置标识为PREPRESSED
如果115后,没有抬起,会将View的标识设置为PRESSED且去掉PREPRESSED标识,然后发出一个检测长按的延迟任务,延时为:ViewConfiguration.getLongPressTimeout() - delayOffset(500ms -115ms),这个115ms刚好时检测额PREPRESSED时间;也就是用户从DOWN触发开始算起,如果500ms内没有抬起则认为触发了长按事件:
1、如果此时设置了长按的回调,则执行长按时的回调,且如果长按的回调返回true;才把mHasPerformedLongPress置为ture;
2、否则,如果没有设置长按回调或者长按回调返回的是false;则mHasPerformedLongPress依然是false;
好了DOWN就分析完成了;大家回个神,下面回到VIEW的onTouchEvent中的ACTION_MOVE:
2、MotionEvent.ACTION_MOVE
86到105行:
87-88行:拿到当前触摸的x,y坐标;
91行判断当然触摸点有没有移出我们的View,如果移出了:
1、执行removeTapCallback();
2、然后判断是否包含PRESSED标识,如果包含,移除长按的检查:removeLongPressCallback();
3、最后把mPrivateFlags中PRESSED标识去除,刷新背景;
[java] view plain copy
- privatevoidremoveTapCallback(){
- if(mPendingCheckForTap!=null){
- mPrivateFlags&=~PREPRESSED;
- removeCallbacks(mPendingCheckForTap);
- }
- }
如果115ms后,你才移出控件外,则你的当前mPrivateFlags一定为PRESSED且发送了长按的检测;
就会走上面的2和3;首先移除removeLongPressCallback()
private void removeLongPressCallback() {
if (mPendingCheckForLongPress != null) {
removeCallbacks(mPendingCheckForLongPress);
}
}
然后把mPrivateFlags中PRESSED标识去除,刷新背景;
好了,MOVE我们也分析完成了,总结一下:只要用户移出了我们的控件:则将mPrivateFlags取出PRESSED标识,且移除所有在DOWN中设置的检测,长按等;
下面再回个神,回到View的onTouchEvent的ACTION_UP:
3、MotionEvent.ACTION_UP
26到69行:
27行:判断mPrivateFlags是否包含PREPRESSED
28行:如果包含PRESSED或者PREPRESSED则进入执行体,也就是无论是115ms内或者之后抬起都会进入执行体。
36行:如果mHasPerformedLongPress没有被执行,进入IF
38行:removeLongPressCallback();移除长按的检测
45-50行:如果mPerformClick如果mPerformClick为null,初始化一个实例,然后立即通过handler添加到消息队列尾部,如果添加失败则直接执行performClick();添加成功,在mPerformClick的run方法中就是执行performClick();
终于执行了我们的click事件了,下面看一下performClick()方法:
[java] view plain copy
- publicbooleanperformClick(){
- sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
- if(mOnClickListener!=null){
- playSoundEffect(SoundEffectConstants.CLICK);
- mOnClickListener.onClick(this);
- returntrue;
- }
- returnfalse;
- }
if (mOnClickListener != null) {
mOnClickListener.onClick(this);
return true;
}
久违了~我们的mOnClickListener ;
别激动,还没结束,回到ACTION_UP,
58行:如果prepressed为true,进入IF体:
为mPrivateFlags设置表示为PRESSED,刷新背景,125毫秒后执行mUnsetPressedState
否则:mUnsetPressedState.run();立即执行;也就是不管咋样,最后mUnsetPressedState.run()都会执行;
看看这个UnsetPressedState主要干什么:
private final class UnsetPressedState implements Runnable {
public void run() {
setPressed(false);
}
}
public void setPressed(boolean pressed) {
if (pressed) {
mPrivateFlags |= PRESSED;
} else {
mPrivateFlags &= ~PRESSED;
}
refreshDrawableState();
dispatchSetPressed(pressed);
}
把我们的mPrivateFlags中的PRESSED取消,然后刷新背景,把setPress转发下去。
ACTION_UP的最后一行:removeTapCallback(),如果mPendingCheckForTap不为null,移除;
4、总结
好了,代码跨度还是相当大的,下面需要总结下:
1、整个View的事件转发流程是:
View.dispatchEvent->View.setOnTouchListener->View.onTouchEvent
在dispatchTouchEvent中会进行OnTouchListener的判断,如果OnTouchListener不为null且返回true,则表示事件被消费,onTouchEvent不会被执行;否则执行onTouchEvent。
2、onTouchEvent中的DOWN,MOVE,UP
DOWN时:
a、首先设置标志为PREPRESSED,设置mHasPerformedLongPress=false ;然后发出一个115ms后的mPendingCheckForTap;
b、如果115ms内没有触发UP,则将标志置为PRESSED,清除PREPRESSED标志,同时发出一个延时为500-115ms的,检测长按任务消息;
c、如果500ms内(从DOWN触发开始算),则会触发LongClickListener:
此时如果LongClickListener不为null,则会执行回调,同时如果LongClickListener.onClick返回true,才把mHasPerformedLongPress设置为true;否则mHasPerformedLongPress依然为false;
MOVE时:
主要就是检测用户是否划出控件,如果划出了:
115ms内,直接移除mPendingCheckForTap;
115ms后,则将标志中的PRESSED去除,同时移除长按的检查:removeLongPressCallback();
UP时:
a、如果115ms内,触发UP,此时标志为PREPRESSED,则执行UnsetPressedState,setPressed(false);会把setPress转发下去,可以在View中复写dispatchSetPressed方法接收;
b、如果是115ms-500ms间,即长按还未发生,则首先移除长按检测,执行onClick回调;
c、如果是500ms以后,那么有两种情况:
i.设置了onLongClickListener,且onLongClickListener.onClick返回true,则点击事件OnClick事件无法触发;
ii.没有设置onLongClickListener或者 onLongClickListener.onClick 返回false, 则 点击事件OnClick事件依然可以触发;d、最后执行mUnsetPressedState.run(),将setPressed传递下去,然后将PRESSED标识去除;
最后问个问题,然后再运行个例子结束:
1、setOnLongClickListener和setOnClickListener是否只能执行一个
不是的,只要setOnLongClickListener中的onClick返回false,则两个都会执行;返回true则会屏幕setOnClickListener
最后我们给MyButton同时设置setOnClickListener和setOnLongClickListener,运行看看:
[java] view plain copy
- packagecom.example.zhy_event03;
- importandroid.app.Activity;
- importandroid.os.Bundle;
- importandroid.util.Log;
- importandroid.view.MotionEvent;
- importandroid.view.View;
- importandroid.view.View.OnClickListener;
- importandroid.view.View.OnLongClickListener;
- importandroid.view.View.OnTouchListener;
- importandroid.widget.Button;
- importandroid.widget.Toast;
- publicclassMainActivityextendsActivity
- {
- protectedstaticfinalStringTAG="MyButton";
- privateButtonmButton;
- @Override
- protectedvoidonCreate(BundlesavedInstanceState)
- {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.activity_main);
- mButton=(Button)findViewById(R.id.id_btn);
- mButton.setOnTouchListener(newOnTouchListener()
- {
- @Override
- publicbooleanonTouch(Viewv,MotionEventevent)
- {
- intaction=event.getAction();
- switch(action)
- {
- caseMotionEvent.ACTION_DOWN:
- Log.e(TAG,"onTouchACTION_DOWN");
- break;
- caseMotionEvent.ACTION_MOVE:
- Log.e(TAG,"onTouchACTION_MOVE");
- break;
- caseMotionEvent.ACTION_UP:
- Log.e(TAG,"onTouchACTION_UP");
- break;
- default:
- break;
- }
- returnfalse;
- }
- });
- mButton.setOnClickListener(newOnClickListener()
- {
- @Override
- publicvoidonClick(Viewv)
- {
- Toast.makeText(getApplicationContext(),"onclick",Toast.LENGTH_SHORT).show();
- }
- });
- mButton.setOnLongClickListener(newOnLongClickListener()
- {
- @Override
- publicbooleanonLongClick(Viewv)
- {
- Toast.makeText(getApplicationContext(),"setOnLongClickListener",Toast.LENGTH_SHORT).show();
- returnfalse;
- }
- });
- }
- }
可以看到LongClickListener已经ClickListener都触发了~
最后,本篇博文完成了对View的事件分发机制的整个流程的说明,并且对源码进行了分析;
当然了,View结束,肯定到我们的ViewGroup了,请点击:Android ViewGroup事件分发机制
更多相关文章
- Android(安卓)View的点击事件分发机制
- Android(安卓)模拟MotionEvent事件 触发输入法
- androidsetClickable不起作用没…
- Android触摸事件传递机制系列详解
- android keydown touch事件传递
- Android(安卓)实现事件监听器的五种处理方法
- android 初识EventBus
- 关于Android的一些理解
- Android事件1-开发指南-用户界面-事件处理