Question

I want to periodically updated a ListView in a ListActivity. I know I can do this easily with an AsyncTask subclass, but out of interest I thought I’d look at using a ScheduledThreadPoolExecutor and the android.app.Activity.runOnUiThread(Runnable action) method.

I release I may be having a ‘senior moment’, but problem is I can only seem to get it to work by nesting runnable, as both ScheduledThreadPoolExecutor.scheduleAtFixedRate and runOnUiThread require a Runnable as a parameter.

Here is my working code:

private void setUpPageUpdater()
{
    listUpdaterExecuter = new ScheduledThreadPoolExecutor(NUM_LIST_UPDATER_THREADS);
    listUpdaterExecuter.scheduleAtFixedRate(new PageUpdater1(), 5, 5, TimeUnit.SECONDS);
}

class PageUpdater1 implements Runnable
{
    @Override
    public void run()
    {
        runOnUiThread(new PageUpdater2());
    }
}

class PageUpdater2 implements Runnable
{
    @Override
    public void run()
    {
        updateList();
    }
}

    private synchronized void updateList()
{
    pages.clear();
    pages.addAll(RetrievedPageProvider.getInstance().getPages());
    sortList();
    adapter.notifyDataSetChanged();
}

Is there a nicer way to code this?

Thanks in advance.

Answer 1

Hint: You don’t need to synchronize updateList. It’s performed on a single thread anyway.

Example with anonymous instances:

private void setUpPageUpdater() {
    listUpdaterExecuter = new ScheduledThreadPoolExecutor(NUM_LIST_UPDATER_THREADS);
    listUpdaterExecuter.scheduleAtFixedRate(new Runnable() {
        private Runnable update = new Runnable() {
            @Override
            public void run() {
                updateList();
            }
        };

        @Override
        public void run() {
            runOnUiThread(update);
        }
    }, 5, 5, TimeUnit.SECONDS);
}