android的全局定时器AlarmManager详解

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AlarmManager对象配合Intent使用，可以定时开启一个Activity，发送一个BroadCast或者开启一个Service。

AlarmManager有如下用法：

（1）在指定时间后，执行某操作

Intent intent=new Intent(this,ShowUtil.class);
PendingIntent sender=PendingIntent.getBroadcast(this, 0, intent, 0);
AlarmManager alarm=(AlarmManager)getSystemService(ALARM_SERVICE);
alarm.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()+4*1000, sender);//4秒后执行

（2）周期性执行某动作

Intent intent=new Intent(this,ShowUtil.class);
PendingIntent sender=PendingIntent.getBroadcast(this, 0, intent, 0);
AlarmManager alarm=(AlarmManager)getSystemService(ALARM_SERVICE);
alarm.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() 5*1000, sender);//每5秒执行一次
//alarm.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), 5*1000, sender);//每5秒执行一次

（3）关于同时定义多个定时器和关闭指定定时器

public static PendingIntent sender1;
public static PendingIntent sender2;
Intent intent=new Intent(this,ShowUtil.class);
sender1=PendingIntent.getBroadcast(this, 1, intent, 0);//第二个参数，用来标识不同的send
sender2=PendingIntent.getBroadcast(this, 2, intent, 0);
AlarmManager alarm=(AlarmManager)getSystemService(ALARM_SERVICE);
alarm.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 2*1000, sender1);
alarm.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 5*1000, sender2);
//在其他地方
AlarmManager alarm=(AlarmManager)getSystemService(ALARM_SERVICE);
alarm.cancel(**.sender1);
alarm.cancel(**.sender2);