ProgressDialog does not show up right away

Question

I am trying to fetch data from internet, parse it and then show the data to the user. The action usually takes 3 seconds or so, and I would like to a spinner ProgressDialog show a message saying that I am loading data. The problem is that ProgressDialog only shows up when the loading is almost complete. This is my code

@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Button load_routes = (Button)findViewById(R.id.load_routes);

    load_routes.setOnClickListener(new View.OnClickListener()
    {
        public void onClick(View v)
        {
            task_complete = false;
            progressBar = new ProgressDialog(v.getContext());
            progressBar.setCancelable(false);
            progressBar.setMessage("Fetching routes data ...");
            progressBar.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            progressBar.show();

            if(haveNetworkConnection())
            {
                loading_routes_data(v);
            }
            else
            {
                progressBar.dismiss();
            }
        }
    });
}

And this is my function that gets called onclick

private void loading_routes_data(View v)
{
    try
    {
        new Thread(new Runnable()
        {
            public void run()
            {
                while(!task_complete)
                {
                    refresh_routes();
                    try
                    {
                        Thread.sleep(1000);
                    }
                    catch(InterruptedException e)
                    {
                        e.printStackTrace();
                    }
                }
                runOnUiThread(new Runnable()
                {
                    public void run()
                    {
                        progressBar.dismiss();
                    }
                });
            }
        }).start();
    }
    catch(Exception e)
    {
    }

    while(!task_complete)
    {
    }
}

My refresh_routes() function gets the data, parses it and then sets task_complete to true, I am not even sure on whether or not I should keep it inside the while loop.

So that is my huge problem. I would like to display ProgressDialog right away on button click, then I would like to call refresh_routes(), and once refresh_routes() is complete I would like to get rid of progress dialog. But I am unsure as to how to go about doing that.

If someone could show me how to go about solving the problem with some article as an example or something like that I will be really grateful. Thank you in advance :)

Answer 1

You're locking the UI thread by calling while(!task_complete) at the end of your method. You really should be using an AsyncTask for an operation like this. Here's what your AsyncTask should look like:

private class MyAsyncTask extends AsyncTask<Void, Void, Void> {

    private ProgressDialog progressDialog;
    private Context context;

    public MyAsyncTask(Context context) {

        this.context = context;
    }

    @Override
    protected void onPreExecute() {

        super.onPreExecute();
        progressDialog = ProgressDialog.show( context, null, "Fetching routes data ..." );
    }

    @Override
    protected Void doInBackground( Void... params ) {

        while (!task_complete) {
            refresh_routes();
            try {
                Thread.sleep( 1000 );
            }
            catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        return null;
    }

    @Override
    protected void onPostExecute( Void result ) {

        super.onPostExecute( result );
        progressDialog.dismiss();
    }
}

To execute this, you would do this:

new MyAsyncTask( this ).execute();

I'm not sure how your refresh_routes() method works, but you might consider moving it's functionality inside the doInBackground() method.

Answer 2

Use AsyncTask to do this. It gives you great feature to perform multi-threading with in an Activity.