Android: CountDownTimer skips last onTick()!

Question

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 "".

Answer 1

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.

Answer 2

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>

Answer 3

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();

Answer 4

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.