Refresh ListView in Fragment after reloading data

Question

I know there are a tonne of answers on SO for this but I can't seem to get it working how I'd like. I have a SherlockFragment containing a ListView which is populated by some data retrieving from a file. I've added a refresh button to the Fragment, the idea being that when you press it it retrieves any changes in the file and adds them to the view if necessary. I also added the popular PullToRefresh library.

Unfortunately, nothing changes however when I reload the Fragment (for example, rotating the device) I can see the new data. I've read about notifyDataSetChanged() but it isn't working for me. The only thing I've gotten working is calling mPager.notifyDataSetChanged() from my main FragmentActivity class and having the following set in my ViewPager adapter:

@Override
public int getItemPosition(Object object) {
    return POSITION_NONE;
}

This accomplishes what I want, but it's not very sleek about it, and you can see it forcing the reload as it were. I'm currently using PullToRefresh and it forces it off page abruptly and quite frankly it just looks bad. To put it bluntly I need to call onCreateView of my Fragment from my AsyncTask reloading the data.

If needed I'll post code, there's just a lot of it so I wouldn't want to post anything unneeded.

Oh, and please note I tried notifyDataSetChanged() in the onPostExecute() of my task.

Thanks for any guidance.

maybe you could use the `Observer Pattern` where your Fragment is a listener and the subject is your AsyncTask, is almost the same way as you accomplished it but is a more elegant way and maybe just maybe you won't see the forcing reload (im not really sure about this). — jac1013, Aug 09 '13 at 02:28
@JosephChilberry It's quite an annoying problem, I found a solution less noticeable (See below in a minute) but it's still not perfect. — whitfin, Aug 09 '13 at 02:31

whitfin · Accepted Answer · 2013-08-11T00:03:55.007

I found a way around this but it's not perfect, so I won't accept this in case something better comes along.

Because upon return to my Fragment onResume() is called (this answer is also pretty specific to my project), I just did the following:

@Override 
public void onResume(){
    super.onResume();
    // Make the adapter again
    adapter = new FeedListAdapter(this, feed);
    // Set it to the list again
    list.setAdapter(adapter); 
}

This refreshes the list (badly) and is still fairly noticeable, although if I use a button instead of PullToRefresh it isn't.

My solution (however bad) alongside PullToRefresh is to stick it in a handler with a delayed trigger to let the pulled down "refresh" section disappear before it runs.

@Override 
public void onResume(){
    super.onResume();
    new Handler().postDelayed(new Runnable() { 
        public void run() { 
            adapter = new FeedListAdapter(this, feed);
            list.setAdapter(adapter); 
        } 
    }, 500); 
}

Again, this is pretty specific to my project and a very strange way of doing it, so any "perfect" answer please share :)

EDIT: There was still an issue with it being a bit jumpy with PullToRefresh, so my solution was to wait in a new thread until the PullToRefresh is hidden again, then rebuild the list (it's messy, but it works so whatever):

@Override 
public void onResume(){
    super.onResume();
    // Start a new thread
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                // Wait until the PullToRefresh is hidden
                synchronized(this){
                    wait(190);
                }
            } catch(InterruptedException ex) { }
            // Post a new runnable
            threadHandler.post(new Runnable(){
                public void run(){
                        // Recreate the adapter from the new feed
                        adapter = new FeedListAdapter(FeedListActivity.this, feed);
                        // Set the recreated adapter
                        list.setAdapter(adapter); 
                    }
                });
            }
        }).start();
    }
}

EDIT 2:

Just noticed I missed something obvious. I just changed my list.onRefreshComplete(); for the PullToRefresh view to my onResume() and the jumpiness was taken care of. Still, I think the above solution is more impressive :p

So my code:

@Override 
public void onResume(){
    super.onResume();
    // Recreate the adapter from the new feed
    adapter = new FeedListAdapter(this, feed);
    // Set the recreated adapter
    list.setAdapter(adapter); 
    // The list has finished refreshing
    list.onRefreshComplete();
}

it's ok if it works, but i would prefer `Observer Pattern` over `Handler`, if you want an example of the approach i commented here it is: http://stackoverflow.com/questions/17350950/loading-listener-screen-while-data-downloads-from-server/17353548#17353548 let me know if you need a more "specific" example. — jac1013, Aug 09 '13 at 02:53
@JosephChilberry Thanks for the example, I'm trying that method now — whitfin, Aug 09 '13 at 03:01
@JosephChilberry I think I understand where you're coming from, but how do I use that to update the list? — whitfin, Aug 09 '13 at 03:07
Me: "is almost the same way as you accomplished it but is a more elegant way and maybe just maybe you won't see the forcing reload (im not really sure about this)" if is not too much work you could post code to get a deeper understanding and see if really there is a better approach for your specific issue or you could just leave it as it works. — jac1013, Aug 09 '13 at 03:38

Refresh ListView in Fragment after reloading data

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