Android Threading Issue

Question

Here's the situation: I've got some lengthy non-UI code that needs to be run in a ListActivity and then have this ListActivity update the UI to contain a the result of this lengthy method (the list). I need a ProgressDialog to be running until it's finished so the user has some feedback.

Here's the code:

public class SolutionListActivity extends ListActivity
{

    private String[] solutions;
    private String letters;
    private ProgressDialog dialog;
    private static Solver solver;


    /** Called when the activity is first created.
     * @param savedInstanceState
     */
    @Override
    public void onCreate(Bundle savedInstanceState)
    { 
        super.onCreate(savedInstanceState);

            //Get the selected letters from LettersActivity
        letters = getIntent().getStringExtra("letters");

        dialog = ProgressDialog.show(this, "Please Wait...",
                    "Searching Words...", true);



        new Thread()
        {
            @Override
            public void run()
            {
                if (solver == null) 
                {
                    solver = new Solver(SolutionListActivity.this);
                    solver.readDictionary(0);
                    solver.readDictionary(1);
                }
                solutions = solver.solve(letters);

                runOnUiThread(new Runnable()
                {
                    @Override
                    public void run()
                    {
                        dialog.dismiss();
                        //Set up a UI List
                        setListAdapter(new ArrayAdapter<String>(SolutionListActivity.this, R.layout.list_item, solutions));

                        ListView lv = getListView();
                        lv.setTextFilterEnabled(true);


                    }
                });

            }
        }.start();

The problem is my ProgressDialog won't dismiss and I can't be sure whether the solutions = solver.solve(letters); will be finished before the UI uses it in setListAdapter(new ArrayAdapter<String>(SolutionListActivity.this, R.layout.list_item, solutions));

Any advice you guys have would be helpful.

Thank You, Calum

Answer 1

Have you tried AsyncTask? It´s built exactly for having threading AND be able to update things in your UI Thread.

Take a look here: http://developer.android.com/resources/articles/painless-threading.html