Adding a persistent multiple-choice or single-choice list

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    mSelectedItems = new ArrayList();  // Where we track the selected items
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    // Set the dialog title
    builder.setTitle(R.string.pick_toppings)
    // Specify the list array, the items to be selected by default (null for none),
    // and the listener through which to receive callbacks when items are selected
           .setMultiChoiceItems(R.array.toppings, null,
                      new DialogInterface.OnMultiChoiceClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which,
                       boolean isChecked) {
                   if (isChecked) {
                       // If the user checked the item, add it to the selected items
                       mSelectedItems.add(which);
                   } else if (mSelectedItems.contains(which)) {
                       // Else, if the item is already in the array, remove it 
                       mSelectedItems.remove(Integer.valueOf(which));
                   }
               }
           })
    // Set the action buttons
           .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int id) {
                   // User clicked OK, so save the mSelectedItems results somewhere
                   // or return them to the component that opened the dialog
                   ...
               }
           })
           .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int id) {
                   ...
               }
           });

    return builder.create();
}

Starting Activities and Getting Results

 public class MyActivity extends Activity {
     ...

     static final int PICK_CONTACT_REQUEST = 0;

     protected boolean onKeyDown(int keyCode, KeyEvent event) {
         if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
             // When the user center presses, let them pick a contact.
             startActivityForResult(
                 new Intent(Intent.ACTION_PICK,
                 new Uri("content://contacts")),
                 PICK_CONTACT_REQUEST);
            return true;
         }
         return false;
     }

     protected void onActivityResult(int requestCode, int resultCode,
             Intent data) {
         if (requestCode == PICK_CONTACT_REQUEST) {
             if (resultCode == RESULT_OK) {
                 // A contact was picked.  Here we will just display it
                 // to the user.
                 startActivity(new Intent(Intent.ACTION_VIEW, data));
             }
         }
     }
 }