Run a method daily after a fixed time

I have functionality in my app where a user will select the time when he wants to get notifications from the application. In this case, I am taking the input from user in this format 12:00 AM. I wrote a method for creating notifications in my app which is working fine but I want to call that method every day at a user-selected time. Also, if app is completely destroyed not even running in the background will this method be called at the user-selected time daily?

String user_time=tinyDB.getString("app_check_time"); // This is user selected time e.g, 12:00 PM
Calendar calendar = Calendar.getInstance();
Date date1 = null;
try {
    date1=new SimpleDateFormat("h:m a").parse(user_time);
} catch (ParseException e) {
    e.printStackTrace();
}
calendar.set(Calendar.HOUR_OF_DAY, date1.getHours());
calendar.set(Calendar.MINUTE, date1.getMinutes());
Date time = calendar.getTime();
System.out.println("hourr  "+time);
timer = new Timer();
timer.schedule(new createNotification(), time);

Have you considered using something like Quartz Scheduler? This library has a mechanism for scheduling tasks to run at a set period of time every day using a cron like expression (take a look at CronScheduleBuilder).

Some example code (not tested):

public class GetDatabaseJob implements InterruptableJob
{
    public void execute(JobExecutionContext arg0) throws JobExecutionException
    {
        getFromDatabase();
    }
}

public class Example
{
    public static void main(String[] args)
    {
        JobDetails job = JobBuilder.newJob(GetDatabaseJob.class);

        // Schedule to run at 5 AM every day
        ScheduleBuilder scheduleBuilder = 
                CronScheduleBuilder.cronSchedule("0 0 5 * * ?");
        Trigger trigger = TriggerBuilder.newTrigger().
                withSchedule(scheduleBuilder).build();

        Scheduler scheduler = StdSchedulerFactory.getDefaultScheduler();
        scheduler.scheduleJob(job, trigger);

        scheduler.start();

}
}

There's a bit more work upfront, and you may need to rewrite your job execution code, but it should give you more control over how you want you job to run. Also it would be easier to change the schedule should you need to

You can use WorkManager for this. And yes, it'll run even if your app is completely dead.

From Android Docs:

>> WorkManager is a library used to enqueue deferrable work that is guaranteed to execute sometime after its Constraints are met.

You can see the guide here https://developer.android.com/topic/libraries/architecture/workmanager

>> The WorkManager API makes it easy to schedule deferrable, asynchronous tasks that are expected to run even if the app exits or device restarts.

Hope it helps!

Creating a long running service for this task

Intent intent = new Intent(this, ReminderService.class);
startService(intent);

Creating a reminderservice which extends service

public class ReminderService extends Service {
@Override
public void onCreate() {
Calendar calendar = Calendar.getInstance();
calendar.set(calendar.get(Calendar.YEAR),
calendar.get(Calendar.MONTH),
calendar.get(Calendar.DAY_OF_MONTH),
6,
0,
0);
setAlarm(calendar.getTimeInMillis());
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// If we get killed, after returning from here, restart
return START_STICKY;
}
public void setAlarm(long timeInMillis) {
AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(this, ReminderReceiver.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this,
0, intent, 0);
if (alarmManager != null) {
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, timeInMillis,
2 * 60 * 1000 , pendingIntent); //AlarmManager.INTERVAL_DAY //2 * 60 * 1000 (2 minutes)
}
}
}

creating ReminderReceiver which extends BroadcastReceiver

public class ReminderReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
//do task to show notification
ShowNotification showNotification = new ShowNotification(context);
showNotification.showNotification("Method called");
}
}

create ShowNotification class

public class ShowNotification {
private static final int NOTIFICATION = 0;
private static final String NOTIFICATION_CHANNEL_ID = "100";
private Context context;
private NotificationManager notificationManager;
private ConnectivityManager conManager;
public ShowNotification(Context context) {
this.context = context;
if (notificationManager == null) {
notificationManager = (NotificationManager) context
.getSystemService(Context.NOTIFICATION_SERVICE);
}
if (conManager == null) {
conManager = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);
}
}
/**
* Show a notification while this service is running.
*
* @param key
*/
void showNotification(String key) {
String NOTIFICATION_CHANNEL_NAME = "NOTIFICATION_CHANNEL_NAME";
// In this sample, we'll use the same text for the ticker and the expanded notification
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
int importance = NotificationManager.IMPORTANCE_LOW;
NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID,
NOTIFICATION_CHANNEL_NAME, importance);
notificationChannel.enableLights(true);
notificationChannel.setLightColor(Color.RED);
notificationChannel.enableVibration(true);
notificationChannel.setVibrationPattern(new long[]{100, 200, 300, 400, 500, 400, 300, 200, 400});
notificationManager.createNotificationChannel(notificationChannel);
}
final Intent notificationIntent = new Intent(context, SplashActivity.class);
notificationIntent.setAction(Intent.ACTION_MAIN);
notificationIntent.addCategory(Intent.CATEGORY_LAUNCHER);
notificationIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
// The PendingIntent to launch our activity if the user selects this notification
PendingIntent contentIntent = PendingIntent.getActivity(context, 0,
notificationIntent, 0);
// Set the info for the views that show in the notification panel.
Notification notification = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID)
.setSmallIcon(android.R.drawable.ic_dialog_alert)
.setWhen(System.currentTimeMillis())
.setContentTitle("Method Called")
.setContentText(key) 
.setContentIntent(contentIntent)  
.setSound(Settings.System.DEFAULT_NOTIFICATION_URI)
.build();
// Send the notification.
notificationManager.cancel(NOTIFICATION);
notificationManager.notify(NOTIFICATION, notification);
}
}

In manifest file

        <service
android:name=".ReminderService"
android:enabled="true"
android:exported="false" />
<receiver android:name=".ReminderReceiver" />