ListView adapter data change without ListView being notified

Question

I\'ve written a ListActivity that has a custom list adapter. The list is being updated from a ContentProvider when onCreate is run. I also have a service that gets started

Answer 1

You have to do all your updating of Adapter data on the UI thread so the synchronized block isn't necessary. It's also useless since your synchronizing on the AsyncTask which is created new each time it's executed.

Another problem is that you are calling notifyDataSetChanged external to the Adapter. You should call it at the end of your setListItems method. That shouldn't be causing errors though since it's being executed on the UI thread but it should not be called in that way.

You should make sure that your getReports method is not modifying the backing store of the Adapter in any way. Since it is running on a separate thread it cannot modify anything the Adapter has access too. Even if it's protected by locks. What you need to do is in your doInBackground method is generate the list of updates or a new list, etc., and pass that into onPostExecute which then commits the new data to the Adapter on the UI thread. So, if your getReports function is changing report_list and your Adapter has a reference to report_list you are doing it wrong. getReports must create a new report_list and then pass that back to your Adapter when it's finished creating it on the UI thread.

To reiterate, you can only modify data the Adapter and subsequently the ListView has access too on the UI thread. Using synchronization/locks does not change this requirement.

Answer 2

If you want to update the UI listview from a service then you should call notifyDataSetChanged() on onDestroy of the service

make the adapter static from your main activity and call that adaptername.notifyDataSetChanged()

like this

@Override
       public void onDestroy() {

               if (MainActivity.isInFront == true) {
                       if (MainActivity.adapter != null)
                               MainActivity.adapter.notifyDataSetChanged();
                       MainActivity.listView.setAdapter(MainActivity.adapter);
               }
}