Question

I want to access activity and set text from async class.

public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Button getBtn = (Button) findViewById(R.id.btn_result);

        getBtn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                           TextView txt_res = (TextView)findViewById(R.id.txt_Result);
                           new GetText(txt_res).execute(); // Async class
                }
        });
    }
}

//Async Class

public class GetText AsyncTask<Void, Void, Void>{
    private TextView txt_res;

    public GetText (TextView txt_res) {
        this.txt_res = txt_res;
    }

    @Override
    protected Void doInBackground(Void... params) {
        try {
                     String Result = GetTextFromDb();
        } catch (Exception e) {

        }
        return null;
    }

     @Override
 protected void onPostExecute(Void result)
    {
        try
        {
            Log.v("Success", "Success"); // I see "Success" at Logcat
            txt_res.SetText("Success"); // Textview didn't change
        }catch (Exception e) {
            Log.v("Error", e.getMessage()); // No error at Logcat

        }
    }
}

I redefine my question. Textview don’t change. Whats my mistake.

I redefine my question again. Textview didn’t change at two functions(doInBackground, onPostExecute)

Answer 1

You basically have 2 options. You cannot directly access the main thread from asych obviously, so you must use the proper format.

1. If the text view needs to be updated after the task finishes, simply do the updating in onPostExecute

2. If the textview is displaying some intermediate progress, use onProgressUpdate

Edit:

Ok so here is your problem now. With asycn tasks, you must return a value from doInBackground. Change the type to String, and change onPostExecute(String result). Void means you are returning nothing. You will also have to change the second of the three parameters at the top of the async task to string as well.

Also, the method is textview.setText(“”); not textview.SetText(“”). The latter should not compile