Question

I’m very new to Android. I’ve used Java before but not for around a year and a half. I’m having problems getting the screen to update, or rather the TextView. I have looked around the net for hours for solutions and I sort of know why its not working, but I don’t know how to fix it.

public class PreliminaryActivity extends Activity {

//private static final int MENU_QUIT = Menu.FIRST;
int i = 0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    getWindow().setBackgroundDrawableResource(R.drawable.background);
    mainComputations();
}

    public void mainComputations(){
        runOnUiThread(new Runnable(){
        //@Override
            public void run(){

                TextView tv = (TextView) findViewById(R.id.time_display);

                tv.setText(new Integer(i).toString());
                i++;
            }
        });
    }

I’ve cut my program down so it should just increment an int value on the screen for testing and it still will not work. Instead it just displays ‘0’. If I add a for loop before the runOnUiThread() method, it will increment the i value but I have a feeling it is simply increasing the value then displaying it rather than it updating in real time. Any help would be greatly appreciated.

Answer 1

In android, You can not update the UI from another thread. This is the restriction (which I consider a feature to remove unncecessary bugs) in android development. You can use AsyncTask for this…

In use, you can perform long task inside donInBackground() and than UI can be updated using onProgressUpdate()… see the AsyncTask example here

EDIT

see this similar question for more information…