Question

Let’s say I have an Activity which displays a View containing a TextView.
My Activity also have an AsyncTask (running continuously) which retrieve data (a changing value) from a web server every second or so.
What I want is to monitor the data from the web server by displaying it in the TextView.

So far I always ask my AsyncTask to do the setText in the onProgressUpdate, so my TextView‘s display is refreshed every time I get new data… is there a better way ?

Thanks for reading me.

PS : In the end, I’ll have at least two Activities, both having an AsyncTask of the previously described variety.

Answer 1

If you want to separate the data and display a bit more, you could follow a listener pattern:

Make your Activity implement a new interface – something like:

public interface boolean OnTextUpdatedListener {
  onTextUpdated(int id, String newText);
}

and the implementation (in your Activity):

@Override
public boolean onTextUpdated(int id, String newText) {
  TextView tv = (TextView)findViewById(id);
  if(tv == null) {
    return false;
  }
  tv.setText(newText);
  return true;
}

And a AsyncTask that looks something like this:

 public class TextUpdater extends AsyncTask<Void, String, Void> {
        OnTextUpdatedListener mListener;
        int mId;
        volatile boolean mRunning;

            public TextUpdater(OnTextUpdatedListener listener, int id) {
        super();
        mListener = listener;
        mId = id;
    }

        @Override
        protected void onProgressUpdate(String... values) {
            mRunning = mListener.onTextUpdated(mId, values[0]);
        }

        @Override
        protected Void doInBackground(Void... params) {
            mRunning = true;
            while(mRunning) {
                //retrieve text from network
                this.publishProgress(downloadedText);
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            mListener = null;
        }
    }

Your Activity keeps control of the UI, the AsyncTask downloads and notifies when something is updated.