Android 开发工具类 17_setAlarm

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Alarm 是在应用程序生命周期之外设置的，所以它们十分适合于调度定时更新或者数据查询，从而避免了在后台持续运行 Service。但触发 Alarm 时，就会广播指定的 Pending Intent。

Alarm 类型：

1、RTC_WAKEUP：在指定的时间唤醒设备，并激活 Pending Intent。

2、RTC：在指定的时间点激活 Pending Intent，但是不会唤醒设备。

3、ELAPSED_REALTIME：根据设备启动之后经过的时间激活 Pending Intent，但是不会唤醒设备。经过的时间包含设备休眠的所有时间。

4、ELAPSED_REALTIME_WAKEUP：在设备启动并经过指定的时间之后唤醒设备和激活 Pending Intent。

 private void setAlarm() {

     /**

      * Listing 9-16: Creating a waking Alarm that triggers in 10 seconds

      */

     // Get a reference to the Alarm Manager

     AlarmManager alarmManager =

      (AlarmManager)getSystemService(Context.ALARM_SERVICE);

     // Set the alarm to wake the device if sleeping.

     int alarmType = AlarmManager.ELAPSED_REALTIME_WAKEUP;

     // Trigger the device in 10 seconds.

     long timeOrLengthofWait = 10000;

     // Create a Pending Intent that will broadcast and action

     String ALARM_ACTION = "ALARM_ACTION";

     Intent intentToFire = new Intent(ALARM_ACTION);

     PendingIntent alarmIntent = PendingIntent.getBroadcast(this, 0,

       intentToFire, 0);

     // Set the alarm

     alarmManager.set(alarmType, timeOrLengthofWait, alarmIntent);

     /**

      * Listing 9-17: Canceling an Alarm

      */

     alarmManager.cancel(alarmIntent);

   }

   private void setInexactRepeatingAlarm() {

     /**

      * Listing 9-18: Setting an inexact repeating alarm

      */

     //Get a reference to the Alarm Manager

     AlarmManager alarmManager =

     (AlarmManager)getSystemService(Context.ALARM_SERVICE);

     //Set the alarm to wake the device if sleeping.

     int alarmType = AlarmManager.ELAPSED_REALTIME_WAKEUP;

     //Schedule the alarm to repeat every half hour.

     long timeOrLengthofWait = AlarmManager.INTERVAL_HALF_HOUR;

     //Create a Pending Intent that will broadcast and action

     String ALARM_ACTION = "ALARM_ACTION";

     Intent intentToFire = new Intent(ALARM_ACTION);

     PendingIntent alarmIntent = PendingIntent.getBroadcast(this, 0,

      intentToFire, 0);

     //Wake up the device to fire an alarm in half an hour, and every

     //half-hour after that.

     alarmManager.setInexactRepeating(alarmType,

                               timeOrLengthofWait,

                               timeOrLengthofWait,

                               alarmIntent);

   }

 }