?
實(shí)驗(yàn)1：使用Java.util.Timer。?
在onStart()創(chuàng)創(chuàng)建Timer，每5秒更新一次計(jì)數(shù)器，并啟動(dòng)。?
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mTimer =
new
?
Timer();???????
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mTimer.schedule(
new
?
TimerTask() {???????????
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????????????
@Override
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????????????
public
?
void
?
run() {
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????????????????
++mCount;
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????????????????
mHandler.sendEmptyMessage(
0
);???????????????
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????????????
}
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????????
},
5
*
1000
,
5
*
1000
);
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當(dāng)連接USB線進(jìn)行調(diào)試時(shí)，會(huì)發(fā)現(xiàn)一切工作正常，每5秒更新一次界面，即使是按下電源鍵，仍然會(huì)5秒觸發(fā)一次。?
當(dāng)拔掉USB線，按下電源鍵關(guān)閉屏幕后，過(guò)一段時(shí)間再打開(kāi)，發(fā)現(xiàn)定時(shí)器明顯沒(méi)有繼續(xù)計(jì)數(shù)，停留在了關(guān)閉電源鍵時(shí)的數(shù)字。?
實(shí)驗(yàn)2：使用AlarmService：?
2.1通過(guò)AlarmService每個(gè)5秒發(fā)送一個(gè)廣播，setRepeating時(shí)的類(lèi)型為AlarmManager.ELAPSED_REALTIME。?
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AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);??
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am.setRepeating(AlarmManager.ELAPSED_REALTIME, firstTime,
5
*
1000
, sender);
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拔掉USB線，按下電源鍵，過(guò)一段時(shí)間再次打開(kāi)屏幕，發(fā)現(xiàn)定時(shí)器沒(méi)有繼續(xù)計(jì)數(shù)。?
2.2setRepeating是的類(lèi)型設(shè)置為AlarmManager.ELAPSED_REALTIME_WAKEUP?
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AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);???
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am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, firstTime,
5
*
1000
, sender);
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拔掉USB線，按下電源鍵，過(guò)一點(diǎn)時(shí)間再次打開(kāi)屏幕，發(fā)現(xiàn)定時(shí)器一直在計(jì)數(shù)。?
如此看來(lái)，使用WAKEUP才能保證自己想要的定時(shí)器一直工作，但是肯定會(huì)引起耗電量的增加
AlarmManager的使用機(jī)制有的稱(chēng)呼為全局定時(shí)器，有的稱(chēng)呼為鬧鐘。通過(guò)對(duì)它的使用，個(gè)人覺(jué)得叫全局定時(shí)器比較合適，其實(shí)它的作用和Timer有點(diǎn)相似。都有兩種相似的用法：（1）在指定時(shí)長(zhǎng)后執(zhí)行某項(xiàng)操作（2）周期性的執(zhí)行某項(xiàng)操作
AlarmManager對(duì)象配合Intent使用，可以定時(shí)的開(kāi)啟一個(gè)Activity,發(fā)送一個(gè)BroadCast,或者開(kāi)啟一個(gè)Service.
下面的代碼詳細(xì)的介紹了兩種定時(shí)方式的使用：
?（1）在指定時(shí)長(zhǎng)后執(zhí)行某項(xiàng)操作
?
- ????? //操作：發(fā)送一個(gè)廣播，廣播接收后Toast提示定時(shí)操作完成 ??
- <!--??
- ??
- Code?highlighting?produced?by?Actipro?CodeHighlighter?(freeware)??
- http: //www.CodeHighlighter.com/ ??
- ??
- -->?????Intent?intent?= new ?Intent(Main. this ,?alarmreceiver. class );??
- ????intent.setAction( "short" );??
- ????PendingIntent?sender=??
- ????????PendingIntent.getBroadcast(Main. this ,? 0 ,?intent,? 0 );??
- ??????
- ???? //設(shè)定一個(gè)五秒后的時(shí)間 ??
- ????Calendar?calendar=Calendar.getInstance();??
- ????calendar.setTimeInMillis(System.currentTimeMillis());??
- ????calendar.add(Calendar.SECOND,? 5 );??
- ??????
- ????AlarmManager?alarm=(AlarmManager)getSystemService(ALARM_SERVICE);??
- ????alarm.set(AlarmManager.RTC_WAKEUP,?calendar.getTimeInMillis(),?sender);??
- ???? //或者以下面方式簡(jiǎn)化 ??
- ???? //alarm.set(AlarmManager.RTC_WAKEUP,?System.currentTimeMillis()+5*1000,?sender); ??
- ??????
- ????Toast.makeText(Main. this ,? "五秒后alarm開(kāi)啟" ,?Toast.LENGTH_LONG).show();??
//注意：receiver記得在manifest.xml注冊(cè)
- <!--??
- ??
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- http: //www.CodeHighlighter.com/ ??
- ??
- -->???? public ? static ? class ?alarmreceiver? extends ?BroadcastReceiver{??
- ??
- ???????? @Override ??
- ???????? public ? void ?onReceive(Context?context,?Intent?intent)?{??
- ???????????? //?TODO?Auto-generated?method?stub ??
- ???????????? if (intent.getAction().equals( "short" )){??
- ????????????????Toast.makeText(context,? "short?alarm" ,?Toast.LENGTH_LONG).show();??
- ????????????} else {??
- ????????????????Toast.makeText(context,? "repeating?alarm" ,???
- ??????????????????????Toast.LENGTH_LONG).show();??
- ????????????}??
- ????????}??
- ????}??
（2）周期性的執(zhí)行某項(xiàng)操作
?
- <!--??
- ??
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- ??
- -->????Intent?intent?= new ?Intent(Main. this ,?alarmreceiver. class );??
- ????intent.setAction( "repeating" );??
- ????PendingIntent?sender=PendingIntent??
- ????????.getBroadcast(Main. this ,? 0 ,?intent,? 0 );??
- ??????
- ??
- ???? //開(kāi)始時(shí)間 ??
- ???? long ?firstime=SystemClock.elapsedRealtime();??
- ??
- ????AlarmManager?am=(AlarmManager)getSystemService(ALARM_SERVICE);??
- ??
- //5秒一個(gè)周期，不停的發(fā)送廣播 ??
- ????am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP??
- ????????????,?firstime,? 5 * 1000 ,?sender);??
?AlarmManager的setRepeating()相當(dāng)于Timer的Schedule(task,delay,peroid);有點(diǎn)差異的地方時(shí)Timer這個(gè)方法是指定延遲多長(zhǎng)時(shí)間
以后開(kāi)始周期性的執(zhí)行task;
AlarmManager的取消：（其中需要注意的是取消的Intent必須與啟動(dòng)Intent保持絕對(duì)一致才能支持取消AlarmManager）
?
?
- <!--??
- ??
- Code?highlighting?produced?by?Actipro?CodeHighlighter?(freeware)??
- http: //www.CodeHighlighter.com/ ??
- ??
- -->??Intent?intent?= new ?Intent(Main. this ,?alarmreceiver. class );??
- ??intent.setAction( "repeating" );??
- ??PendingIntent?sender=PendingIntent??
- ?????????.getBroadcast(Main. this ,? 0 ,?intent,? 0 );??
- ??AlarmManager?alarm=(AlarmManager)getSystemService(ALARM_SERVICE); ?
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