protect Service

startService self

	private void startSelfService() {
		// 获得系统级别服务
		AlarmManager am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
		Intent in = new Intent(this, this.getClass());
		PendingIntent pin = PendingIntent.getService(this, 0, in,
				PendingIntent.FLAG_UPDATE_CURRENT);
		// 返回系统开机到现在的时间差
		long timePeriod = SystemClock.elapsedRealtime();
		// ELAPSED_REALTIME =3s 
		am.setRepeating(AlarmManager.ELAPSED_REALTIME, timePeriod, 3 * 1000,
				pin);
	}