AlarmManager的使用機制有的稱呼為全局定時器,有的稱呼為鬧鐘。通過對它的使用,個人覺得叫全局定時器比較合适,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)周期性的執行某項操作
AlarmManager對象配合Intent使用,可以定時的開啟一個Activity,發送一個BroadCast,或者開啟一個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
代碼
//操作:發送一個廣播,廣播接收後Toast提示定時操作完成
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開啟
"
, Toast.LENGTH_LONG).show();
//注意:receiver記得在manifest.xml注冊
代碼
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)周期性的執行某項操作
代碼
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秒一個周期,不停的發送廣播
am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP
, firstime, 5 * 1000 , sender);
AlarmManager的setRepeating()相當于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
以後開始周期性的執行task;
AlarmManager的取消:(其中需要注意的是取消的Intent必須與啟動Intent保持絕對一緻才能支援取消AlarmManager)
代碼
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);