Android Java - comparing date/time to create a popup.

Posted on 2014-01-13
Last Modified: 2014-01-21
Hi all,

I want to create a popup alert when the time equals the time stored in a string.

I have the date time in a string like this.
strAlertDate = "14-01-2014 00:45:39";

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I then have a timer running which does the comparison.
private Runnable updateTimerThread = new Runnable() {
	public void run() {
		SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
		String currentDateandTime = sdf.format(new Date());
		if(currentDateandTime.equals(strAlertDate)) {
		customHandler.postDelayed(this, 0);

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However this doesn't work. Nothing happens.

Could it be something to do with timezones? Is there a better way?
Question by:mhdi
  • 3
  • 2
LVL 16

Expert Comment

ID: 39778712
Although I don't do Android, it's extremely likely that your Timer resolution isn't right. Your code would certainly work. I ran it with a fixed rate schedule of 1000ms Period, and it was ok. I used a Timer handled by a separate class extending TimerTask.

Author Comment

ID: 39781485
Is there a better way?

The time/date of the alert changes based on other factors. I need to have an alarm go off if the time ever reaches the alert time/date.

Rather then run a timer constantly comparing like above, can I set an alarm in the android system? I would need the ability to remove and recreate the alarm if the alarm time changes before the time is reached.
LVL 16

Expert Comment

ID: 39781860
I don't know if there are alarms you can set in Android. Nearly all I know is that a separate thread timer does work - cf: your comment that "nothing happens".

A separate thread has quite low running costs, at least on desktop Java.

So your requirement actually seems to include a dynamic alarm deadline, which might be redefined before the current alarm deadline is reached - is that right? That anyway sounds like a job for a separate thread responsible for updating the alarm params.

(From where is the alarm deadline issued?)

Author Comment

ID: 39781943
So your requirement actually seems to include a dynamic alarm deadline, which might be redefined before the current alarm deadline is reached - is that right?
That is correct.
(From where is the alarm deadline issued?)
The time and date comes from a webservice. The web service is automatically called every 10 minutes. Occasionally (every few hours) the alarm deadline changes.
LVL 16

Accepted Solution

krakatoa earned 500 total points
ID: 39783153
So these two pieces of code should simulate something like your requirements. This one:

import java.text.*;
import java.util.*;

class Tim extends TimerTask {

String currentDateandTime;
public static Date alarmTime;
SimpleDateFormat  sdf ;

	public Tim(){

		Timer t= new Timer();

	public void run(){

		sdf = new SimpleDateFormat("dd-MM-yyyy HH:mm");
		currentDateandTime = sdf.format(new Date());

		if(currentDateandTime.equals((new SimpleDateFormat("dd-MM-yyyy HH:mm")).format(alarmTime))){


		System.out.println((new SimpleDateFormat("dd-MM-yyyy HH:mm")).format(alarmTime));

		}catch(Exception er){}



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will set off the alarm (just a sysout here of course), and this one :

import java.util.*;
import java.text.*;

class ArmAlarm {

static GregorianCalendar cal = new GregorianCalendar(2014,1,15,18,0);
static int mins = 0;

   public static void main(String[] args){

		Tim tim = new Tim();;

	while (true){


			mins = (int)(Math.random()*60);

			cal.set(2014, 0, 15, 19, mins);

			tim.alarmTime = cal.getTime();						

		}catch(Exception exx){}




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serves the time.

(The way I decided was to use a random minute, so eventually the match will be made, so it takes a few iterations).

I'm not saying this is the answer - we're not near that yet I don't think.

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