Update TextView every second in Android

Question

i want to update my textview every second. on button click i am calling one method,

loopMethod(milli); //suppose milli= 50000 i.e 50 sec.

so my loopMethod(int m) is as follows:

public void loopMethod(int m){
    timer=(TextView) findViewById(R.id.timerText);
    if(m>=1000){
        try {
            timer.setText(""+m);//timer is a textview
            System.out.println(m);
            m=m-1000;
            Thread.sleep(1000);
        } catch(InterruptedException ex) {
            ex.printStackTrace();
        }
        loopMethod(m);
    }
}

so what i am expecting is, my timer textview should print the value of m every second. but i am getting only console output i.e system.out.println(m)... printing value on console working fine... but its not updating my textview at all

Solution 1

You can use following code:

Runnable updater;
void updateTime(final String timeString) {
    timer=(TextView) findViewById(R.id.timerText);
    final Handler timerHandler = new Handler();

    updater = new Runnable() {
        @Override
        public void run() {
            timer.setText(timeString);
            timerHandler.postDelayed(updater,1000);
        }
    };
    timerHandler.post(updater);
}

In this line:

 timerHandler.post(updater);

time will set for the first time. i.e, updater will execute. After first execution it will be posted after every 1 second time interval. It will update your TextView every one second.

You need to remove it when the activity destroys, else it will leak memory.

@Override
protected void onDestroy() {
   super.onDestroy();
   timerHandler.removeCallbacks(updater);
}

Hope it will help you.

Solution 2

You should use RxJava library to do so:

Subscription s =
                Observable.interval(1, TimeUnit.SECONDS)
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(v -> {
                    // update your ui here
                }, e -> {

                });

        // call when you no longer need an update:
        if (s != null && !s.isUnsubscribed()){
            s.unsubscribe();
            s = null;
        }

That's it. Do NOT use .postDelay(), Timer because it is error prone.

Solution 3

You might want to consider using the Chronometer class: https://developer.android.com/reference/android/widget/Chronometer.html

just use timer.start(); on the button click

Comments

[varsha]

facing same problem with above code. :(

[Pier Giorgio Misley]

@varsha look my "Add" section, we need some more code

[varsha]

above code gives error: ---android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. ------------but after adding comments to timer.setText it perfectly displays output on console with system.out.println

[varsha]

i am just taking milliseconds from user and adding as a parameter to loopMethod. and then after clicking on ok button the timer textview should display the decreasing time after every sec. (Just like countdown)

[Pier Giorgio Misley]

@varsha check my updated code

[varsha]

Thank you so much @Ajith Pandian... thanx a lots.. its working as i wanted :D

[Ajith Pandian]

Welcome. Happy coding.

[varsha]

but how to stop it? means i want to stop the updating after my timeString>0...to achieve my output i just added timestring-=1000; after timer.setText. and replace the string data type to int. plz help me. i am not familiar with handler

[Ajith Pandian]

timerHandler.removeCallbacks(updater); to stop the handler thread. you can use this whenever you want.

[varsha]

Yes, working :D

[xanexpt]

exactly what i was looking for :) many thanks