如何在特定时间后发出通知

Question

在特定时间后发布通知需要帮助，在这里看过几个例子，但它对我不起作用。

在按钮上单击一个方法，从现在开始调用AlarmManager 5秒，然后调用我的方法发出通知。 下面是相同的代码。

private void startAlarm() {
        AlarmManager alarmManager = (AlarmManager) this.getSystemService(this.ALARM_SERVICE);

        Calendar rightNow = Calendar.getInstance();
         long when = rightNow.getTimeInMillis()+5000;

        Intent intent = new Intent(this, RemainderService.class);
        PendingIntent pendingIntent = PendingIntent.getService(this, 0, intent, 0);
        alarmManager.set(AlarmManager.RTC_WAKEUP,when,pendingIntent);
    }

来自另一个类（文件）RemainderService.java

public class RemainderService extends IntentService {
    public RemainderService() {
        super("RemainderService");
    }

    private static final int NOTIF_ID = 1;

    @Override
      protected void onHandleIntent(Intent intent) {

        NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        long when = System.currentTimeMillis();         // notification time

        Notification notification = new Notification(R.drawable.icon, "reminder", when);
        notification.defaults |= Notification.DEFAULT_SOUND;
        notification.flags |= notification.FLAG_AUTO_CANCEL;

        Intent notificationIntent = new Intent(this, Notify.class);
        notificationIntent.putExtra("notificationID", 20);

        PendingIntent contentIntent = PendingIntent.getActivity(this, 20, notificationIntent , 0);

        notification.setLatestEventInfo(getApplicationContext(), "It's about time", "You should open the app now", contentIntent);

        nm.notify(NOTIF_ID, notification);
    }
}

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基本的人为错误，忘了在清单文件中添加详细信息。