public class MyCallingClass extends ActivityBase {
    private String _result = null;

    protected void onCreate(Bundle savedInstanceState) {
    callingMethod();
    }

    protected void callingMethod() {
        MyASyncClass whatever = new MyASyncClass(new MyASyncClass.AsyncResponse() {
            @Override
            **void processFinish(String output)**{
                _result = output;
            }
        }).execute();
    }

    // More work done here
}

public class MyASyncClass extends AsyncTask<String, String, String> {
    public interface AsyncResponse {
        void processFinish(String output);
    }

    public AsyncResponse delegate = null;

    public DeviceConnect(AsyncResponse delegate){
        this.delegate = delegate;
    }

    @Override
    protected String doInBackground(String... params) {
    // Does the work
    }

    @Override
    public void onPostExecute(String result) {
        delegate.processFinish(result);
    }
}