Starting a runnable in background thread

Question

I have, to my knowledge, implemented a runnable which is created on a new thread. However, the thread does not seem to be running in the background, and the actions taken inside the runnable are stalling the UI with heavy actions.

See below:

custListLoadThread = new Thread(loadRunnable);
custListLoadThread.run();

private Runnable loadRunnable = new Runnable()
{
    @Override
    public void run()
    {
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_BACKGROUND);

        Gen.popup("TEST"); // Creates a toast pop-up.
        // This is to know if this runnable is running on UI thread or not!

        try
        {               
            customers = Db.BasicArrays.getCustomers(CustomApp.Session.businessCode, empId);

            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    populate();
                    setCustListVisible(true);
                    loading = false;
                }
            });
        }
        catch (final Exception ex)
        {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Gen.popup(ex.getMessage());
                }
            });
        }
    }
};

However this code does not run in the background, it still seems to run on the UI thread. I have placed the line Gen.popup("TEST"); to make sure of this (calling a toast pop up in a non-UI thread should cause an error).

Any ideas as to why this runnable isn't running in the background?

Strickman

Answer 1

custListLoadThread = new Thread(loadRunnable);
custListLoadThread.start();

You need to start the thread, not call the run() method in the current thread.

Judaism

That was the problem, thanks very much! Got caught out by the similarities of run and start! – Strickman

Answer 2

If you want to execute code on a background thread that does not do something with the UI:

    Runnable runnable = new Runnable() {
        @Override
        public void run() {
            //your action
        }
    };
    AsyncTask.execute(runnable);

Of course as written before you can also create a new thread (that is independent from the UI thread):

    new Thread(runnable).start();

In your example you want to update UI elements, so better use a AsyncTask (must be called from UI thread!):

    new AsyncTask<Void, Void, Void>() {
        @Override
        protected Void doInBackground(Void... params) {
            // your async action
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            // update the UI (this is executed on UI thread)
            super.onPostExecute(aVoid);
        }
    }.execute();

Twit