Question

I am trying to poll a given website periodically for information and then in turn update the UI in an Android app.

I have set something up similar to the following, but it just seems cumbersome. I guess my two specific questions would be:

1. Is the view.post(new Runnable()); necessary or are the broadcasts handled on the UI thread (allowing the AsyncTask to be executed directly since it must be done from the UI)?

2. Is there any way to periodically start an AsyncTask (or something comparable) besides setting up the alarms and receiving the Intents?

Here is a simplified version of what I am running:

public class WebUpdates extends BroadcastReceiver
{

private AlarmManager am ;
private PendingIntent pi ;
private View view ; 
private Context listener ; 

public WebUpdates(Context listener, View view)
{
    this.listener= listener; 
    this.view = view ;

    am = (AlarmManager)listener.getSystemService(Context.ALARM_SERVICE) ;
    pi = PendingIntent.getBroadcast((Context)listener, 0, new Intent("WEBUPDATE"), 0) ;

    am.setInexactRepeating(AlarmManager.ELAPSED_REALTIME, 0, (long)15000, pi) ;
}

@Override
public void onReceive(Context context, Intent intent) 
{
    view.post(new Runnable() {
        public void run()
        {
            new WebUpdateTask().execute() ;
        }
    }) ;
}

private class WebUpdateTask extends AsyncTask<Void, Void, Void>
{
    @Override
    protected Void doInBackground(Void... v) 
    {
        // bunch of web stuff... 
    }

    public void onPostExecute(Void v)
    {
        view.doBunchOfUpdates() ;
    }
}
}

This is my first question, so I apologize for for any formatting issues. Any input or help would be much appreciated!

Answer 1

1. According to the documentation, onReceive() exceutes on the main thread. So you ought to be able to start the AsyncTask directly.
2. Another option would be to use Timer and TimerTask. There are a number of examples on the web, here is one. AlarmManager is better if you need to receive the Intent even when your Activity is not active. Timer and TimerTask might be better if you only need the periodic behavior while your Activity is running. Oh and I guess ScheduledThreadPoolExecutor is preferred for new code; I’ve just used Timer/TimerTask in the past.

But I don’t think there is any harm in using AlarmManager even if you only need to update when your app is being used, as long as you cancel the alarm in onPause().