Android(安卓)关于倒计时功能的实现

关于倒计时的实现，可以说有很多的方法，比较常见的就是Timer+TimerTask+Handler了，或者还可以配合Runnable。例如下面的代码：

[html] view plain copy

importjava.util.Timer;
importjava.util.TimerTask;
importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.os.Message;
importandroid.util.Log;
importandroid.view.View;
importandroid.widget.Button;
importandroid.widget.TextView;
publicclassMainActivityextendsActivity{
Timertimer;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
finalTextViewtv=(TextView)findViewById(R.id.textView1);
Buttonb=(Button)findViewById(R.id.button1);
//定义Handler
finalHandlerhandler=newHandler(){
@Override
publicvoidhandleMessage(Messagemsg){
super.handleMessage(msg);
//handler处理消息
if(msg.what>0){
tv1.setText(""+msg.what);
}else{
//在handler里可以更改UI组件
tv.setText("倒时");
timer.cancel();
}
}
};
b.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewarg0){
//定义计时器
timer=newTimer();
//定义计划任务，根据参数的不同可以完成以下种类的工作：在固定时间执行某任务，在固定时间开始重复执行某任务，重复时间间隔可控，在延迟多久后执行某任务，在延迟多久后重复执行某任务，重复时间间隔可控
timer.schedule(newTimerTask(){
inti=10;
//TimerTask是个抽象类,实现的是Runable类
@Override
publicvoidrun(){
//定义一个消息传过去
Messagemsg=newMessage();
msg.what=i--;
handler.sendMessage(msg);
}
},1000,200);
}
});
}
}

基本逻辑就是这样，需要注意一点是 timer.schedule(task,1000,5000),如果设置为 timer.schedule(task,5000)是不会工作的。因为timer.schedule(task,5000) 是表示执行一次的任务。timer.schedule(task,1000,5000)表示1 秒钟后开始 5 秒钟为周期的重复执行任务。

这个例子北京简单，下面给出一个完整的例子：

[html] view plain copy

importjava.util.Timer;
importjava.util.TimerTask;
importcom.example.jishiqi.SaveRun;
importandroid.app.Activity;
importandroid.app.AlertDialog;
importandroid.content.DialogInterface;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.os.Message;
importandroid.view.View;
importandroid.view.View.OnClickListener;
importandroid.widget.Button;
importandroid.widget.TextView;
publicclassMainActivityextendsActivity{
Buttonbtnselecttime,daojishijicubutton;
TextViewtvTime;
privateTimertimer=null;
privateTimerTasktask=null;
privateHandlerhandler=null;
privateMessagemsg=null;
floatpredegree=0;
floatsecondpredegree=0;
floathourpredegree=0;
intmlCount=-1;
@Override
publicvoidonCreate(Bundleicicle){
super.onCreate(icicle);
setContentView(R.layout.main);
btnselecttime=(Button)findViewById(R.id.daojishistartbutton);
daojishijicubutton=(Button)findViewById(R.id.daojishijicubutton);
tvTime=(TextView)findViewById(R.id.daojishitvTime);
SaveRun.setisdaojishi(false);
handler=newHandler(){
@Override
publicvoidhandleMessage(Messagemsg){
switch(msg.what){
case1:
mlCount--;
if(mlCount<=0){
enddaojishi();
}
inttotalSec=0;
intyushu=0;
totalSec=(int)(mlCount/10);
yushu=(int)(mlCount%10);
intmin=(totalSec/60);
intsec=(totalSec%60);
try{
tvTime.setText(String.format("%1$02d:%2$02d.%3$d",min,
sec,yushu));
predegree=(float)(0.6*mlCount);
secondpredegree=(float)(36.0*mlCount);
hourpredegree=(float)(mlCount/100);
}catch(Exceptione){
tvTime.setText(""+min+":"+sec+"."+yushu);
e.printStackTrace();
}
break;
default:
break;
}
super.handleMessage(msg);
}
};
}
privatevoidenddaojishi(){
try{
task.cancel();
task=null;
timer.cancel();
timer.purge();
timer=null;
handler.removeMessages(msg.what);
newAlertDialog.Builder(MainActivity.this)
.setTitle("提示")
.setMessage("倒计时结束")
.setPositiveButton("确定",
newDialogInterface.OnClickListener(){
@Override
publicvoidonClick(DialogInterfacedialog,
intwhich){
dialog.cancel();
mlCount=600;
btnselecttime.setText("开始");
SaveRun.setisdaojishi(false);
}
}).setCancelable(false).create().show();
}catch(Exceptione){
e.printStackTrace();
}
}
@Override
protectedvoidonStart(){
daojishijicubutton.setOnClickListener(newOnClickListener(){
@Override
publicvoidonClick(Viewv){
predegree=0;
secondpredegree=0;
hourpredegree=0;
mlCount=-1;
btnselecttime.setText("开始");
SaveRun.setisdaojishi(false);
try{
if(task!=null){
task.cancel();
task=null;
timer.cancel();
timer.purge();
timer=null;
handler.removeMessages(msg.what);
}
}catch(Exceptione){
e.printStackTrace();
}
}
});
btnselecttime.setOnClickListener(newOnClickListener(){
@Override
publicvoidonClick(Viewarg0){
if(null==timer){
if(mlCount==-1||mlCount==0){
mlCount=600;
}
if(mlCount>0){
SaveRun.setisdaojishi(true);
btnselecttime.setText("暂停");
if(null==task){
task=newTimerTask(){
@Override
publicvoidrun(){
if(null==msg){
msg=newMessage();
}else{
msg=Message.obtain();
}
msg.what=1;
handler.sendMessage(msg);
}
};
}
timer=newTimer(true);
timer.schedule(task,100,100);
}
}else{
try{
SaveRun.setisdaojishi(false);
btnselecttime.setText("继续");
task.cancel();
task=null;
timer.cancel();
timer.purge();
timer=null;
handler.removeMessages(msg.what);
}catch(Exceptione){
e.printStackTrace();
}
}
}
});
super.onStart();
}
}

布局：

[html] view plain copy

<?xmlversion="1.0"encoding="utf-8"?>
<RelativeLayoutxmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TextView
android:id="@+id/daojishitvTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/daojishibuttonlinear"
android:layout_centerInParent="true"
android:text="00:00.0"
android:textSize="35sp"
android:textStyle="bold"/>
<LinearLayout
android:id="@+id/daojishibuttonlinear"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="74sp"
android:background="@drawable/v5_bottom_bar_bg_light"
android:orientation="horizontal">
<Button
android:id="@+id/daojishistartbutton"
android:layout_width="wrap_content"
android:layout_height="50sp"
android:layout_gravity="center_vertical"
android:layout_marginLeft="8sp"
android:layout_marginRight="3sp"
android:layout_weight="1"
android:background="@drawable/startbutton"
android:text="开始"/>
<Button
android:id="@+id/daojishijicubutton"
android:layout_width="wrap_content"
android:layout_height="50sp"
android:layout_gravity="center_vertical"
android:layout_marginLeft="3sp"
android:layout_marginRight="8sp"
android:layout_weight="1"
android:background="@drawable/startbutton"
android:text="取消"/>
</LinearLayout>
</LinearLayout>
</RelativeLayout>

显然，这个方式比较笨拙，我们可以对此进行一个封装，利用Handler和Eunnable，看下面的代码：

[html] view plain copy

packagecom.example.daojishi;
importandroid.os.Handler;
importandroid.util.Log;
publicclassMyCountDownTimer{
privatelongmillisInFuture;
privatelongcountDownInterval;
privatebooleanstatus;
publicMyCountDownTimer(longpMillisInFuture,longpCountDownInterval){
this.millisInFuture=pMillisInFuture;
this.countDownInterval=pCountDownInterval;
status=false;
Initialize();
}
publicvoidStop(){
status=false;
}
publiclonggetCurrentTime(){
returnmillisInFuture;
}
publicvoidStart(){
status=true;
}
publicvoidInitialize(){
finalHandlerhandler=newHandler();
Log.v("status","starting");
finalRunnablecounter=newRunnable(){
publicvoidrun(){
longsec=millisInFuture/1000;
if(status){
if(millisInFuture<=0){
Log.v("status","done");
}else{
Log.v("status",Long.toString(sec)+"secondsremain");
millisInFuture-=countDownInterval;
handler.postDelayed(this,countDownInterval);
}
}else{
Log.v("status",Long.toString(sec)
+"secondsremainandtimerhasstopped!");
handler.postDelayed(this,countDownInterval);
}
}
};
handler.postDelayed(counter,countDownInterval);
}
}

这个类就是负责倒计时的类，下面结合Activity，看一下怎么用：

[html] view plain copy

packagecom.example.daojishi;
importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.os.Handler;
importandroid.util.Log;
importandroid.view.View;
importandroid.widget.Button;
importandroid.widget.TextView;
publicclassCounterActivityextendsActivity{
/**Calledwhentheactivityisfirstcreated.*/
TextViewtimeText;
ButtonstartBut;
ButtonstopBut;
MyCountDownTimermycounter;
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
timeText=(TextView)findViewById(R.id.time);
startBut=(Button)findViewById(R.id.start);
stopBut=(Button)findViewById(R.id.stop);
mycounter=newMyCountDownTimer(20000,1000);
RefreshTimer();
}
publicvoidStartTimer(Viewv){
Log.v("startbutton","开始倒计时");
mycounter.Start();
}
publicvoidStopTimer(Viewv){
Log.v("stopbutton","暂停倒计时");
mycounter.Stop();
}
publicvoidRefreshTimer(){
finalHandlerhandler=newHandler();
finalRunnablecounter=newRunnable(){
publicvoidrun(){
timeText.setText(Long.toString(mycounter.getCurrentTime()));
handler.postDelayed(this,100);
}
};
handler.postDelayed(counter,100);
}
}

布局文件：

[html] view plain copy

<?xmlversion="1.0"encoding="utf-8"?>
<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:weightSum="1">
<TextView
android:id="@+id/time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
android:textAppearance="?android:attr/textAppearanceLarge">
</TextView>
<Button
android:id="@+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="StartTimer"
android:text="Start">
</Button>
<Button
android:id="@+id/stop"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="StopTimer"
android:text="Stop">
</Button>
</LinearLayout>

这样就可以比较方便地使用倒计时功能了。但是还有一个更简单的方法。

在Android中有一个CountDownTimer类，这个类就是用来实现类似倒计时方面的功能。使用的时候，只需要继承自CountDownTimer并实现它的方法。

[html] view plain copy

importandroid.app.Activity;
importandroid.os.Bundle;
importandroid.content.Intent;
importandroid.os.CountDownTimer;
importandroid.widget.TextView;
importandroid.widget.Toast;
publicclassNewActivityextendsActivity{
privateMyCountmc;
privateTextViewtv;
@Override
protectedvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tv=(TextView)findViewById(R.id.show);
mc=newMyCount(30000,1000);
mc.start();
}
/*定义一个倒计时的内部类*/
classMyCountextendsCountDownTimer{
publicMyCount(longmillisInFuture,longcountDownInterval){
super(millisInFuture,countDownInterval);
}
@Override
publicvoidonFinish(){
tv.setText("done");
}
@Override
publicvoidonTick(longmillisUntilFinished){
tv.setText("secondsremaining:"+millisUntilFinished/1000）;
}
}
}

onFinish()方法是本次倒计时结束的时候调用的，onTick是每隔1秒钟执行的，我们就是在这里执行重复的任务，像本例子的显示时间。执行完后会自动取消，如果在期间停止的话，可以调用cancel()方法。看一下它的源码就会发现，它是使用Handler+SystemClock来实现的。

[html] view plain copy

/*
*Copyright(C)2008TheAndroidOpenSourceProject
*
*LicensedundertheApacheLicense,Version2.0(the"License");
*youmaynotusethisfileexceptincompliancewiththeLicense.
*YoumayobtainacopyoftheLicenseat
*
*http://www.apache.org/licenses/LICENSE-2.0
*
*Unlessrequiredbyapplicablelaworagreedtoinwriting,software
*distributedundertheLicenseisdistributedonan"ASIS"BASIS,
*WITHOUTWARRANTIESORCONDITIONSOFANYKIND,eitherexpressorimplied.
*SeetheLicenseforthespecificlanguagegoverningpermissionsand
*limitationsundertheLicense.
*/
packageandroid.os;
importandroid.util.Log;
/**
*Scheduleacountdownuntilatimeinthefuture,with
*regularnotificationsonintervalsalongtheway.
*
*Exampleofshowinga30secondcountdowninatextfield:
*
*<preclass="prettyprint">
*newCountDownTimer(30000,1000){
*
*publicvoidonTick(longmillisUntilFinished){
*mTextField.setText("secondsremaining:"+millisUntilFinished/1000);
*}
*
*publicvoidonFinish(){
*mTextField.setText("done!");
*}
*}.start();
*</pre>
*
*Thecallsto{@link#onTick(long)}aresynchronizedtothisobjectsothat
*onecallto{@link#onTick(long)}won'teveroccurbeforetheprevious
*callbackiscomplete.Thisisonlyrelevantwhentheimplementationof
*{@link#onTick(long)}takesanamountoftimetoexecutethatissignificant
*comparedtothecountdowninterval.
*/
publicabstractclassCountDownTimer{
/**
*Millissinceepochwhenalarmshouldstop.
*/
privatefinallongmMillisInFuture;
/**
*Theintervalinmillisthattheuserreceivescallbacks
*/
privatefinallongmCountdownInterval;
privatelongmStopTimeInFuture;
/**
*@parammillisInFutureThenumberofmillisinthefuturefromthecall
*to{@link#start()}untilthecountdownisdoneand{@link#onFinish()}
*iscalled.
*@paramcountDownIntervalTheintervalalongthewaytoreceive
*{@link#onTick(long)}callbacks.
*/
publicCountDownTimer(longmillisInFuture,longcountDownInterval){
mMillisInFuture=millisInFuture;
mCountdownInterval=countDownInterval;
}
/**
*Cancelthecountdown.
*/
publicfinalvoidcancel(){
mHandler.removeMessages(MSG);
}
/**
*Startthecountdown.
*/
publicsynchronizedfinalCountDownTimerstart(){
if(mMillisInFuture<=0){
onFinish();
returnthis;
}
mStopTimeInFuture=SystemClock.elapsedRealtime()+mMillisInFuture;
mHandler.sendMessage(mHandler.obtainMessage(MSG));
returnthis;
}
/**
*Callbackfiredonregularinterval.
*@parammillisUntilFinishedTheamountoftimeuntilfinished.
*/
publicabstractvoidonTick(longmillisUntilFinished);
/**
*Callbackfiredwhenthetimeisup.
*/
publicabstractvoidonFinish();
privatestaticfinalintMSG=1;
//handlescountingdown
privateHandlermHandler=newHandler(){
@Override
publicvoidhandleMessage(Messagemsg){
synchronized(CountDownTimer.this){
finallongmillisLeft=mStopTimeInFuture-SystemClock.elapsedRealtime();
if(millisLeft<=0){
onFinish();
}elseif(millisLeft<mCountdownInterval){
//notick,justdelayuntildone
sendMessageDelayed(obtainMessage(MSG),millisLeft);
}else{
longlastTickStart=SystemClock.elapsedRealtime();
onTick(millisLeft);
//takeintoaccountuser'sonTicktakingtimetoexecute
longdelay=lastTickStart+mCountdownInterval-SystemClock.elapsedRealtime();
//specialcase:user'sonTicktookmorethanintervalto
//complete,skiptonextinterval
while(delay<0)delay+=mCountdownInterval;
sendMessageDelayed(obtainMessage(MSG),delay);
}
}
}
};
}

所以，如果你的程序需要执行一些周期性的任务，就可以考虑使用CountDownTimer这个类了。需要注意的是，在上面的这个例子中，最后显示时间是1，也就是说其实上执行了29次。所以这个地方一定要注意，如果你的任务次数是n，那么设置的时候一定要注意设置成n+1的时间。

最后，欢迎大家评论交流，谢谢。

更多相关文章

随机推荐