Schedule a TimerTask at specific time once per day

问题:

I have a TimerTask object timerTask. My code is running but when service gets started initially, my timer task runs instantly before the specified time i.e. 3:30 PM, though I want it to run on 3:30 PM once per day only.

Calendar cal = Calendar.getInstance();
cal.set(Calendar.AM_PM, Calendar.PM);
cal.set(Calendar.HOUR, 3);    
cal.set(Calendar.MINUTE, 30);
cal.set(Calendar.SECOND, 0);
Date date = cal.getTime();
timer.schedule(timerTask, date, 1000*60*60*24); // once per day

回答1:

As other community users suggested, don't use Timertask, android has a AlarmManager

that you can use.

HOW?

1. Register the alarm manager with a broadcast receiver, there override the onReceive method (what to do when the alamr is fired)
2. Set the alarm with the interval daily and the time to be executed.

---

Here a Snippet as Example:

public class MainActivity extends Activity {
private static final String TAG ="MainActivity";
PendingIntent myPendingIntent;
AlarmManager alarmManager;
BroadcastReceiver myBroadcastReceiver;
Calendar firingCal;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //Register AlarmManager Broadcast receive.
    firingCal= Calendar.getInstance();
    firingCal.set(Calendar.HOUR, 8); // At the hour you want to fire the alarm
    firingCal.set(Calendar.MINUTE, 0); // alarm minute 
    firingCal.set(Calendar.SECOND, 0); // and alarm second
    long intendedTime = firingCal.getTimeInMillis();

    registerMyAlarmBroadcast();
    alarmManager.set( AlarmManager.RTC_WAKEUP, intendedTime , AlarmManager.INTERVAL_DAY , myPendingIntent );
}

private void registerMyAlarmBroadcast()
{
      Log.i(TAG, "Going to register Intent.RegisterAlramBroadcast");

    //This is the call back function(BroadcastReceiver) which will be call when your 
    //alarm time will reached.
    myBroadcastReceiver = new BroadcastReceiver()
    {
        @Override
        public void onReceive(Context context, Intent intent)
        {
            Log.i(TAG,"BroadcastReceiver::OnReceive()");
            Toast.makeText(context, "Your Alarm is there", Toast.LENGTH_LONG).show();
        }
    };

    registerReceiver(myBroadcastReceiver, new IntentFilter("com.alarm.example") );
    myPendingIntent = PendingIntent.getBroadcast( this, 0, new Intent("com.alarm.example"),0 );
    alarmManager = (AlarmManager)(this.getSystemService( Context.ALARM_SERVICE ));
}
private void UnregisterAlarmBroadcast()
{
    alarmManager.cancel(myPendingIntent); 
    getBaseContext().unregisterReceiver(myBroadcastReceiver);
}

@Override
protected void onDestroy() {
    unregisterReceiver(myBroadcastReceiver);
    super.onDestroy();
}
}

---

Edit:

if the time can changed dynamically in the App depending on user-inputs, then just change the Calender firingCal variable for adjusting the time.