AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE); |
am.setRepeating(AlarmManager.ELAPSED_REALTIME, firstTime, 5 * 1000 , sender); |
拔掉USB線,按下電源鍵,過一段時間再次打開屏幕,發現定時器沒有繼續計數。
2.2setRepeating是的類型設置爲AlarmManager.ELAPSED_REALTIME_WAKEUP
AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE); |
am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, firstTime, 5 * 1000 , sender); |
拔掉USB線,按下電源鍵,過一點時間再次打開屏幕,發現定時器一直在計數。
如此看來,使用WAKEUP才能保證自己想要的定時器一直工作,但是肯定會引起耗電量的增加
AlarmManager的使用機制有的稱呼爲全局定時器,有的稱呼爲鬧鐘。通過對它的使用,個人覺得叫全局定時器比較合適,其實它的作用和Timer有點相似。都有兩種相似的用法:(1)在指定時長後執行某項操作(2)週期性的執行某項操作
AlarmManager對象配合Intent使用,可以定時的開啓一個Activity,發送一個BroadCast,或者開啓一個Service.
下面的代碼詳細的介紹了兩種定時方式的使用:
(1)在指定時長後執行某項操作
- //操作:發送一個廣播,廣播接收後Toast提示定時操作完成
- <!--
- Code highlighting produced by Actipro CodeHighlighter (freeware)
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- --> Intent intent =new Intent(Main.this, alarmreceiver.class);
- intent.setAction("short");
- PendingIntent sender=
- PendingIntent.getBroadcast(Main.this, 0, intent, 0);
- //設定一個五秒後的時間
- 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);
- //或者以下面方式簡化
- //alarm.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()+5*1000, sender);
- Toast.makeText(Main.this, "五秒後alarm開啓", Toast.LENGTH_LONG).show();
//注意:receiver記得在manifest.xml註冊
- <!--
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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)週期性的執行某項操作
- <!--
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- http://www.CodeHighlighter.com/
- --> Intent intent =new Intent(Main.this, alarmreceiver.class);
- intent.setAction("repeating");
- PendingIntent sender=PendingIntent
- .getBroadcast(Main.this, 0, intent, 0);
- //開始時間
- long firstime=SystemClock.elapsedRealtime();
- AlarmManager am=(AlarmManager)getSystemService(ALARM_SERVICE);
- //5秒一個週期,不停的發送廣播
- am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP
- , firstime, 5*1000, sender);
AlarmManager的setRepeating()相當於Timer的Schedule(task,delay,peroid);有點差異的地方時Timer這個方法是指定延遲多長時間
以後開始週期性的執行task;
AlarmManager的取消:(其中需要注意的是取消的Intent必須與啓動Intent保持絕對一致才能支持取消AlarmManager)
- <!--
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- 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);
- alarm.cancel(sender);