Question

Hey i recently got into android and made my first app which was meant to start a run down timer of 60 seconds when the user pressed start button. The application sets the content view fine and displays 60 but when i click the start button it displays 59 successfully and then the app crashes.Here’s the code(it has only one activity)

public class test1activity extends Activity 
{   
Thread countdown;
long f, pa, jee;
TextView ytvp;
String s;
TextView uyti;
@Override   
public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ytvp = (TextView) findViewById(R.id.textView2);
        uyti = (TextView) findViewById(R.id.tv2);

countdown = new Thread() {
            public void run() {
                jee = (System.currentTimeMillis()) / 1000;
                while ((((System.currentTimeMillis()) / 1000) - jee) < 60)
                                {                   
                                try {   
                    sleep(1000);    
                } catch (InterruptedException e) {                  
                    e.printStackTrace();    
                } finally {
                    f = ((System.currentTimeMillis()) / 1000) - jee;
                        pa = 60 - f;    
                        s = String.valueOf(pa);
                        ytvp.setText(s);
                    }
                }
                                }
                };
    }       
public void whenclickstart(View view) {
        countdown.start();
    }       

Answer 1

You cannot set UI elements from inside another thread(Non UI thread). So you cannot use this below line.

 ytvp.setText(s);

Try something like this, you dont need threading for what you are trying to do

new CountDownTimer(60000, 1000) {

     public void onTick(long millisUntilFinished) {
         ytvp.setText("" + millisUntilFinished/1000);
     }

     public void onFinish() {
          ytvp.setText(""+0);
     }
  }.start();

If you do not want to use countdowntimer replace setText with

runOnUiThread(new Runnable() {
    public void run() {
        ytvp.setText(s);
    }
});