Do some Android UI stuff in non-UI thread

Question

Is there a way to do UI changes in a non-UI thread? Short question.

Answer 1

Either use Handler or use below code

    runOnUiThread(new Runnable()
    {           
        @Override
        public void run()
        {
            // Ui Stuff here                
        }
    });

Answer 2

There are many way to do this, use AsyncTask or Threads. Short answer.

^{_{Hint: the UI stuff can be done in the pre-postExecute/runOnUiThread/Handler class}}

Answer 3

If you dont want to use an AsyncTask, try the observer pattern with an inner class (ResponseHandler) in your main activity, sorry I couldnt get the formatting right but im sure you get the idea

public class WorkerThread extends Observable implements Runnable {
public void run() {
    try {
            DoSomething();
            String response = "Doing something";
            setChanged();
            notifyObservers( response );
            DoSomethingElse();
            String response = "Doing something else";
            setChanged();
            notifyObservers( response );
    }
    catch (IOException e) {
        e.printStackTrace();
    }
}
private void DoSomething(){
}
private void DoSomethingElse(){
}


public class MainActivity{
public class ResponseHandler implements Observer {
    private String resp;
    public void update (Observable obj, Object arg) {
        if (arg instanceof String) {
            resp = (String) arg;
            //Write message to UI here ie System.out.println("\nReceived Response: "+ resp );
            //or EditText et = (EditText)findViewById(R.id.blah);
            // blah.SetText(resp);
        }
    }
}
private void doStuffAndReportToUI(){
    final WorkerThread wt = new WorkerThread();
    final ResponseHandler respHandler = new ResponseHandler();
    wt.addObserver( respHandler );
    Thread thread = new Thread(wt);
    thread.start();
}

Answer 4

Check out the Handler class. Or take a look at these similar questions:

Update UI from Thread

Handling UI code from a Thread

updating the ui from thread using audiotrack

Answer 5

I tried +tmho answer, but it still gives this error:

E/AndroidRuntime(****): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

I finally end up combinning it with +ingsaurabh way, like that:

private class ResponseHandler implements Observer, Runnable {

    Activity act;

    public ResponseHandler(Activity caller) {
        act = caller;
    }

    @Override
    public void update (Observable obj, Object arg) {
        act.runOnUiThread(this);
    }

    @Override
    public void run() {
        //update UI here
    }
}

thanks both of you.

Answer 6

Try to explore runOnUIThread()

http://developer.android.com/reference/android/app/Activity.html#runOnUiThread(java.lang.Runnable)