Android: CountDownTimer skips last onTick()!

Code: > public class SMH extends Activity {
> > public void onCreate(Bundle b) {
> super.onCreate(b);
> setContentView(R.layout.main);
> > TextView tv = (TextView) findViewById(R.id.tv);
> > new CountDownTimer(10000, 2000) {
> public void onTick(long m) {
> long sec = m/1000+1;
> tv.append(sec+" seconds remain\n");
> }
> public void onFinish() {
> tv.append("Done!");
> }
> }.start();
> }

Output:
10 seconds remain
8 seconds remain
6 seconds remain
4 seconds remain
Done!

Problem:

How do I get it to show "2 seconds remain"? The time elapsed is indeed 10 seconds, but the last onTick() never happens. If I change the second parameter from 2000 to 1000, then this is the output:

10 seconds remain
9 seconds remain
8 seconds remain
7 seconds remain
6 seconds remain
5 seconds remain
4 seconds remain
3 seconds remain
2 seconds remain
Done!

So you see, it seems to be skipping that last onTick() call. And btw, the XML file is basically the default main.xml with the TextView assigned the id tv and the text set to "".

I checked the source code of CountDownTimer. The "missing tick" comes from a special feature of CountDownTimer that I have not yet seen being documented elsewhere:

At the start of every tick, before onTick() is called, the remaining time until the end of the countdown is calculated. If this time is smaller than the countdown time interval, onTick is not called anymore. Instead only the next tick (where the onFinish() method will be called) is scheduled.

Given the fact that hardware clocks are not always super precise, that there may be other processes in the background that delay the thread running CountDownTimer plus that Android itself will probably create a small delay when calling the message handler of CountDownTimer it is more than likely that the call for the last tick before the end of the count down will be at least one millisecond late and therefore onTick() will not be called.

For my application I solved this problem simply by making the tick intervals "slightly" smaller (500 ms)

    myCountDownTimer = new CountDownTimer(countDownTime, intervalTime - 500) {
                                   ...
    }

and I could leave my code just as it is. For applications where the length of the interval time is critical, the other solutions posted here are probably the best.

I don't know why the last tick is not working but you can create your own timer with Runable , for example.

class MyCountDownTimer {
	private long millisInFuture;
	private long countDownInterval;
	public MyCountDownTimer(long pMillisInFuture, long pCountDownInterval) {
			this.millisInFuture = pMillisInFuture;
			this.countDownInterval = pCountDownInterval;
		}
	public void Start() 
	{
		final Handler handler = new Handler();
		Log.v("status", "starting");
		final Runnable counter = new Runnable(){

		    public void run(){
		    	if(millisInFuture <= 0) {
		    		Log.v("status", "done");
		    	} else {
	    		    long sec = millisInFuture/1000;
	    		    Log.v("status", Long.toString(sec) + " seconds remain");
	    		    millisInFuture -= countDownInterval;
	    		    handler.postDelayed(this, countDownInterval);
		    	}
		    }
		};

		handler.postDelayed(counter, countDownInterval);
	}
}

and to start it,

new MyCountDownTimer(10000, 2000).Start();

---

EDIT FOR GOOFY'S QUESTION

you should have a variable to hold counter status (boolean) . then you can write a Stop() method like Start().

EDIT-2 FOR GOOFY'S QUESTION

actually there is no bug on stopping counter but there is a bug on start again after stop(resume).

I'm writing a new updated full code that I had just tried and it's working. It's a basic counter that show time on screen with start and stop button.

class for counter

public class MyCountDownTimer {
    private long millisInFuture;
    private long countDownInterval;
    private boolean status;
    public MyCountDownTimer(long pMillisInFuture, long pCountDownInterval) {
            this.millisInFuture = pMillisInFuture;
            this.countDownInterval = pCountDownInterval;
            status = false;
            Initialize();
    }
    
    public void Stop() {
    	status = false;
    }
    
    public long getCurrentTime() {
    	return millisInFuture;
    }
    
    public void Start() {
    	status = true;
    }
    public void Initialize() 
    {
        final Handler handler = new Handler();
        Log.v("status", "starting");
        final Runnable counter = new Runnable(){
        	
            public void run(){
            	long sec = millisInFuture/1000;
            	if(status) {
	                if(millisInFuture <= 0) {
	                    Log.v("status", "done");
	                } else {
	                    Log.v("status", Long.toString(sec) + " seconds remain");
	                    millisInFuture -= countDownInterval;
	                    handler.postDelayed(this, countDownInterval);
	                }
            	} else {
            		Log.v("status", Long.toString(sec) + " seconds remain and timer has stopped!");
            		handler.postDelayed(this, countDownInterval);
            	}
            }
        };

        handler.postDelayed(counter, countDownInterval);
    }
}

activity class

public class CounterActivity extends Activity {
    /** Called when the activity is first created. */
	TextView timeText;
    Button startBut;
    Button stopBut;
    MyCountDownTimer mycounter;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        timeText = (TextView) findViewById(R.id.time);
        startBut = (Button) findViewById(R.id.start);
        stopBut = (Button) findViewById(R.id.stop);
        mycounter = new MyCountDownTimer(20000, 1000);
        RefreshTimer();
    }
    
    public void StartTimer(View v) {
    	Log.v("startbutton", "saymaya basladi");
    	mycounter.Start();
    }
    
    public void StopTimer(View v) {
    	Log.v("stopbutton", "durdu");
    	mycounter.Stop();
    }
    
    public void RefreshTimer() 
    {
        final Handler handler = new Handler();
        final Runnable counter = new Runnable(){
        	
            public void run(){
            	timeText.setText(Long.toString(mycounter.getCurrentTime()));
            	handler.postDelayed(this, 100);
            }
        };

        handler.postDelayed(counter, 100);
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:weightSum="1">
    <TextView android:textAppearance="?android:attr/textAppearanceLarge" 
    		  android:text="TextView" android:layout_height="wrap_content" 
    		  android:layout_width="wrap_content" 
    		  android:id="@+id/time">
    </TextView>
    <Button android:text="Start" 
    		android:id="@+id/start" 
    		android:layout_width="wrap_content" 
    		android:layout_height="wrap_content" 
    		android:onClick="StartTimer">
    </Button>
    <Button android:text="Stop" 
    		android:id="@+id/stop" 
    		android:layout_width="wrap_content" 
    		android:layout_height="wrap_content" 
    		android:onClick="StopTimer">
   	</Button>
</LinearLayout>

I've spent hours trying to figure out this problem, and I'm happy to show you a nice work around. Don't bother waiting for the onFinish() call, just add 1 (or whatever your interval is) to your units, then add an if statement in the onTick() calls. Just do your onFinish() task(s) on the last onTick(). Here's what I've got:

	new CountDownTimer( (countDownTimerValue + 1) * 1000, 1000) { //Added 1 to the countdownvalue before turning it into miliseconds by multiplying it by 1000.
		public void onTick(long millisUntilFinished) {

          //We know that the last onTick() happens at 2000ms remaining (skipping the last 1000ms tick for some reason, so just throw in this if statement.
			if (millisUntilFinished < 2005){ 
				//Stuff to do when finished.
			}else{
				mTextField.setText("Time remaining: " + (((millisUntilFinished) / 1000) - 1));	//My textfield is obviously showing the remaining time. Note how I've had to subtrack 1 in order to display the actual time remaining.
			}
		}

		public void onFinish() {
		//This is when the timer actually finishes (which would be about 1000ms later right? Either way, now you can just ignore this entirely.
			
			
		}
	}.start();

The most simple solution I came up with is as follows. Note that it only works if you need a simple screen to display with a seconds countdown.

mTimer = new CountDownTimer(5000, 100){
			public void onTick(long millisUntilFinished) {
				mTimerView.setText(Long.toString(millisUntilFinished/1000));				
		     }

		     public void onFinish() {
		    	 mTimerView.setText("Expired");
		     }
		};
		
		mTimer.start();

In the code above the onTick() is called every 100 milliseconds but visually only seconds are displayed.

While the solution above is valid, it can be further improved. It unnecessarily has a runnable inside another class (which can already be treated on it's own). So just create a class that extends a thread (or runnable).

    class MyTimer extends Thread {
      private long millisInFuture;
      private long countDownInterval;
      final Handler mHandler = new Handler();
      
      public MyTimer(long pMillisInFuture, long pCountDownInterval) {
        this.millisInFuture = pMillisInFuture;
        this.countDownInterval = pCountDownInterval;
      }
      
      public void run() {
        if(millisInFuture <= 0) {
          Log.v("status", "done");
        } else {
          millisInFuture -= countDownInterval;
          mHandler.postDelayed(this, countDownInterval);
        }
      }
    }

I found easy solution. I need CountDown to update ProgressBar, so I did this:

new CountDownTimer(1000, 100) {
    
    private int counter = 0;
    
    @Override
    public void onTick(long millisUntilFinished) {
        Log.d(LOG_TAG, "Tick: " + millisUntilFinished);
        if (++counter == 10) {
            timeBar.setProgress(--lenght); // timeBar and lenght defined in calling code
            counter = 0;
        }
    }

    
    @Override
    public void onFinish() {
        Log.d(LOG_TAG, "Finish.");
    
        timeBar.setProgress(0);
    }

};

Small tick do the trick :)

So I think I went a little over board because my timer runs in its own thread instead of using postDelay handlers, though it always posts back to the thread it was created in. I also knew that I only cared about seconds so its simplified around that idea. It also lets you cancel it and restart it. I do not have pausing built in because that's not in my needs.

/**
* Created by MinceMan on 8/2/2014.
*/
public abstract class SecondCountDownTimer {

private final int seconds;
private TimerThread timer;
private final Handler handler;

/**
 * @param secondsToCountDown Total time in seconds you wish this timer to count down.
 */
public SecondCountDownTimer(int secondsToCountDown) {
    seconds = secondsToCountDown;
    handler = new Handler();
    timer = new TimerThread(secondsToCountDown);
}

/** This will cancel your current timer and start a new one.
 *  This call will override your timer duration only one time. **/
public SecondCountDownTimer start(int secondsToCountDown) {
    if (timer.getState() != State.NEW) {
        timer.interrupt();
        timer = new TimerThread(secondsToCountDown);
    }
    timer.start();
    return this;
}

/** This will cancel your current timer and start a new one. **/
public SecondCountDownTimer start() {
    return start(seconds);
}

public void cancel() {
    if (timer.isAlive()) timer.interrupt();
    timer = new TimerThread(seconds);
}

public abstract void onTick(int secondsUntilFinished);
private Runnable getOnTickRunnable(final int second) {
    return new Runnable() {
        @Override
        public void run() {
            onTick(second);
        }
    };
}

public abstract void onFinish();
private Runnable getFinishedRunnable() {
    return new Runnable() {
        @Override
        public void run() {
            onFinish();
        }
    };
}

private class TimerThread extends Thread {

    private int count;

    private TimerThread(int count) {
        this.count = count;
    }

    @Override
    public void run() {
        try {
            while (count != 0) {
                handler.post(getOnTickRunnable(count--));
                sleep(1000);
            }
        } catch (InterruptedException e) { }
        if (!isInterrupted()) {
            handler.post(getFinishedRunnable());
        }
    }
}

}

To expand on Nantoka's answer. Here's my code to ensure the view is updated correctly:

countDownTimer = new CountDownTimer(countDownMsec, 500) 
{
    public void onTick(long millisUntilFinished)
    {
        if(millisUntilFinished!=countDownMsec)
        {
            completedTick+=1;
            if(completedTick%2==0)      // 1 second has passed
            {
                // UPDATE VIEW HERE based on "seconds = completedTick/2"
            }
            countDownMsec = millisUntilFinished;  // store in case of pause
        }
    }

    public void onFinish()
    {
        countDownMsec = 0;
        completedTick+=2;       // the final 2 ticks arrive together
        countDownTimer = null;

        // FINAL UPDATE TO VIEW HERE based on seconds = completedTick/2 == countDownMsec/1000
    }
}

I also faced the same issue with CountDownTimer and I tried different approaches. So one of the easiest ways is in solution provided by @Nantoca - he suggests to double the frequency from 1000ms to 500ms. But I don't like this solution because it makes more work which will consume some extra battery resource.

So I decided to use @ocanal's soultion and to write my own simple CustomCountDownTimer.

But I found couple of flaws in his code:

1. It's a bit inefficient (creating second handler to publish results)

2. It starts to publish first result with a delay. (You need to do a post() method rather than postDelayed() during first initialization)

3. odd looking. Methods with capital letter, status instead of classic isCanceled boolean and some other.

So I cleaned it a bit and here is the more common version of his approach:

private class CustomCountDownTimer {

    private Handler mHandler;
    private long millisUntilFinished;
    private long countDownInterval;
    private boolean isCanceled = false;

    public CustomCountDownTimer(long millisUntilFinished, long countDownInterval) {
        this.millisUntilFinished = millisUntilFinished;
        this.countDownInterval = countDownInterval;
        mHandler = new Handler();
    }

    public synchronized void cancel() {
        isCanceled = true;
        mHandler.removeCallbacksAndMessages(null);
    }

    public long getRemainingTime() {
        return millisUntilFinished;
    }

    public void start() {

        final Runnable counter = new Runnable() {

            public void run() {

                if (isCanceled) {
                    publishUpdate(0);
                } else {

                    //time is out
                    if(millisUntilFinished <= 0){
                        publishUpdate(0);
                        return;
                    }

                    //update UI:
                    publishUpdate(millisUntilFinished);

                    millisUntilFinished -= countDownInterval;
                    mHandler.postDelayed(this, countDownInterval);
                }
            }
        };

        mHandler.post(counter);
    }
}

if Your time Interval is more than 4 sec then every onTick() call would not be proper. So if you want precise result then keep interval less than 5 sec. The Reseaon is at the start of every tick, before onTick() is called, the remaining time until the end of the countdown is calculated and If this time is smaller than the countdown time interval, onTick() would not not called anymore. Instead only the next tick (where the onFinish() method will be called) is scheduled.

Add a few milliseconds to your timer to allow it time to process the code. I added +100 to your timer-length, and also Math.ceil() to round up the result, rather than adding 1.

Also... the first tick is AFTER 2000 millis, so you won't get a "10 seconds left" entry unless you add it.

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

    final TextView tv = (TextView) findViewById(R.id.tv);
    tv.setText("10 Seconds remain\n"); //displayed before the first tick.
    new CountDownTimer(10000+25, 1000) { //25 to account for processing time
        public void onTick(long m) {
            long sec = (long) Math.ceil(m / 2000 ); //round up, don't add 1
            tv.append(sec + " seconds remain\n");
        }
        public void onFinish() {
            tv.append("Done!");
        }
    }.start();
}

You are calculating time remaining incorrectly. The callback gets the number of milliseconds until completion of the task.

public void onTick(long m) {  
    long sec = m/1000+1;  
    tv.append(sec+" seconds remain\n");  
}  

should be

public void onTick(long m) {  
    long sec = m/1000;  
    tv.append(sec+" seconds remain\n");  
}

I've never used this class myself but it looks like you will not get a callback the instant it starts, which is why it appears like you're missing an entry. e.g. 10000 ms, 1000 ms per tick you'd get a total of 9 update callbacks, not 10 - 9000, 8000, 7000, 6000, 5000, 4000, 3000, 2000, 1000, finish.