Question

I have a simple function that shows loading spinner while fetching data (usually takes 7 seconds or so)

private void load_data(View v)
{
    task_complete = false;
    progressBar = new ProgressDialog(v.getContext());
    progressBar.setCancelable(false);
    progressBar.setMessage("Fetching data ...");
    progressBar.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    progressBar.show();

    try
    {
        Log.v("thread", "Starting thread");
        new Thread(new Runnable()
        {
            public void run()
            {
                while(!task_complete)
                {
                    fetch_data();
                    try
                    {
                        Thread.sleep(1000);
                    }
                    catch(InterruptedException e)
                    {
                        e.printStackTrace();
                    }
                }
                progressBar.dismiss();
            }
        }).start();
        Log.v("thread", "Thread finished successfully");
    }
    catch(Exception e)
    {
        Log.v("thread", "fail "+e.toString());
    }
}

The problem I have is that the function gets called by onClick via

load.setOnClickListener(new View.OnClickListener()
{
    public void onClick(View v)
    {
        load_data(v);
        show_data(v); // shows the data on a spinner
    }
});

And when I press the load button the second time I get an error. My log does show

Starting thread
Thread finished successfully

But somehow the app dies with an error saying

03-27 02:48:39.282: E/AndroidRuntime(956): Uncaught handler: thread Thread-9 exiting due to uncaught exception
03-27 02:48:39.293: E/AndroidRuntime(956): android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
03-27 02:48:39.293: E/AndroidRuntime(956):  at android.view.ViewRoot.checkThread(ViewRoot.java:2683)

I would greatly appreciate it if someone can show me or explain to me what causes the error

Answer 1

The problem is that your progressBar.dismiss(); is executed in another thread, to make it run in UI thread, do this:

    runOnUiThread(new Runnable() {

        @Override
        public void run() {
            progressBar.dismiss();
        }
    });