Android: Scheduling a repeating task for short time intervals isn't working

Question

In Android, I have an activity which schedules a task(showing a notification) to repeat for every 10 or 15 mins even if the app is closed or killed.

I have tried to schedule it using AlarmManager with alarmManager.setExact, alarmManager.set and alarmManager.setRepeating and none of them fired the event at exact time. There is a lot of delay in firing the event. Sometimes it fire at exact time and sometimes there will be delay. The delay ranges from 15 mins to several hours.

I saw the android docs saying that AlarmManager will delay the events starting from Lollipop 5.1. I have tried it with Handlers as well as TimerTask and Timer, but they get killed immediately when app is killed.

Is there any alternate solution which runs for short interval times and runs in the background too.

Answer 1

您需要的是Service和CountDownTimer。

启动服务并将倒数计时器初始化10到15分钟，如计时器完成时重新初始化同一计时器并在计时器的onFinish方法中显示通知。

这样，即使应用关闭，您也会显示通知。

Answer 2

更新并运作示例：

这个为特定的日期和时间设置和警报。然后每3分钟重复一次。

MainActivity：

public class MainActivity extends AppCompatActivity {

    private AlarmManager alarmManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Calendar calendar = Calendar.getInstance();
        calendar.setTimeInMillis(System.currentTimeMillis());
        calendar.set(Calendar.HOUR_OF_DAY, 17);
        calendar.set(Calendar.MINUTE, 03);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        calendar.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);

        Intent dailyIntent = new Intent(this, AlarmActivity.class);

        PendingIntent mondayIntent = PendingIntent.getActivity(this, 1000, dailyIntent, 0);

        alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

        if (Build.VERSION.SDK_INT >= 19) {
            alarmManager.setExact(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), mondayIntent);
        } else {
            System.out.println("------------------------");
        }
    }
}

AlarmActivity：

public class AlarmActivity extends Activity {

    private AlarmManager alarmManager;
    Intent intent;
    PendingIntent pendingIntent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.alarm_activity);

        alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        intent = new Intent(this, AlarmActivity.class);
        pendingIntent = PendingIntent.getActivity(this, 1000, intent, 0);

        alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                SystemClock.elapsedRealtime() +
                        60 * 1000 * 3, pendingIntent);
    }
}

希望这有帮助。

修改 另外，请不要忘记在系统重启和打包（您的应用）更新时设置闹钟。