Browser Progress Tracker in Blackberry BrowserField

Has anyone been able to implement a progress tracker bar for a BrowserField in blackberry i'm struggling with this. I want to tell the user that something is actually happening when he opens the browser field in my app.

I already checked the BrowserFieldProgressBar demo, but that only works on OS 6 since it's for BrowserField2. Either a progress bar or a dialog with a gif works. I tried implementin开发者_Python百科g the following, but the PopUpScreen doesn't show over the browser field and once i exit the browserfield it gets stuck:

public class BrowserPopUpScreen extends MainScreen{

    private GridFieldManager _manager;
    private BrowserField _browserField; // Campo de la interfaz que se utiliza para mostrar una página web


    private final String GRAPH_URL = "https://graph.facebook.com"; // URL de Graph API de Facebook.
    private final String NEXT_URL = "http://www.facebook.com/connect/login_success.html"; // URL adonde se redirige al usuario cuando la operacion es exitosa.
    private final String APPLICATION_KEY = "e1812f3b71678c8e0017831cc4cbc87a"; // Llave de la aplicación en Facebook. 
    private final String APPLICATION_SECRET = ""; // Secreto de la aplicacion en Facebook.
    private final String APPLICATION_ID = ""; // ID de la aplicacion en Facebook.

    public static final int FACEBOOK_SIGNUP = 1; // Constante que indica que el usuario desea registrarse con Facebook
    public static final int FACEBOOK_LINK = 2; // Constante que indica que el usuario desea conectar su cuenta de Facebook a la cuenta de Social Voice

    /**
     * Construye la pantalla de browser.
     * 
     * Dependiendo te la acción que recibe en caso de ser FACEBOOK_SIGNUP
     * peticiona en envió de información de usuario a Facebook, en caso contrario
     * solo pide un token de acceso para el usuario.
     * 
     * @param manager
     *          Administrador de contenido que utilizará la pantalla
     * @param action
     *          Acción que se realizará, en caso de ser registro la
     *          acción será FACEBOOK_SIGNUP, en caso de solo conectar 
     *          Fonyk con Facebook será FACEBOOK_LINK
     */
    public BrowserPopUpScreen(GridFieldManager manager, final int action)
    {
        _manager = manager;

        _browserField = new BrowserField();

        // Se crea el URL de la petición y se hace el llamado a dicho URL 
        _browserField.requestContent(new StringBuffer().append("https://graph.facebook.com/oauth/authorize?client_id=").append(APPLICATION_ID).append("&").append("redirect_uri=").append(NEXT_URL).append("&").append("scope=offline_access,publish_stream,email").append("&display=wap").toString());

        final LoadingScreen loadingScreen = new LoadingScreen();
        //Este metodo detecta cuando se realiza un cambio en el BrowserField
        BrowserFieldListener browserListener = new BrowserFieldListener() {

            public void documentLoaded(BrowserField browserField, Document document) throws Exception
            {
                loadingScreen.onClose();
                //Se verifica si es nuestro URL de redirección
                if(_browserField.getDocumentUrl().startsWith(NEXT_URL))
                {

                    String url = _browserField.getDocumentUrl();
                    String code = getElement(url, "code");

                    //Si la petición fue exitosa al URL se le agrega un campo code
                    //revisamos si este no es uno para continuar con la operacion
                    if(!code.equals(""))
                    {

                        //Creamos un cliente http para hacer un GET y obtener el token
                        //de acceso
                        HttpClient httpClient = new HttpClient(MainApp.connFactory);

                        //Se crea un hashtable que va a contener la información de nuestra aplicación
                        //y el código proporcionado previamente
                        Hashtable data = new Hashtable();

                        data.put("client_id", APPLICATION_ID);
                        data.put("redirect_uri", NEXT_URL);
                        data.put("client_secret", APPLICATION_SECRET);
                        data.put("code", code);

                        StringBuffer response = httpClient.doGet(GRAPH_URL.concat("/oauth/access_token"), data);


                        if(response.length() == 0)
                            throw new Exception();

                        //Se obtiene el token de acceso de la respuesta y se asigna a nuestro
                        //objeto usuario
                        String accessToken = getElement(response.toString(), "access_token");

                        MainApp.user.setFacebookAccessToken(accessToken);
                        MainApp.user.setFacebookAccess(true);

                        //Si la acción a realizar es de registro, se utiliza el token de acceso
                        //para peticionar los datos del usuario a FB
                        if(action == FACEBOOK_SIGNUP)
                        {
                            data.clear();
                            data.put("access_token", accessToken);

                            response = null;

                            response = httpClient.doGet(GRAPH_URL.concat("/me"), data);

                            JSONObject jsonResponse = new JSONObject(response.toString());

                            // Al obtener una respuesta se establecen los valores en el objeto definido
                            // inicialmente en la aplicacion
                            MainApp.facebookUserInfo.setFirstName(jsonResponse.optString("first_name"));
                            MainApp.facebookUserInfo.setLastBame(jsonResponse.optString("last_name"));
                            MainApp.facebookUserInfo.setEmail(jsonResponse.optString("email"));
//                          MainApp.facebookUserInfo.set_birthday(jsonResponse.optString("birthday"));
                            MainApp.facebookUserInfo.setGender(jsonResponse.optString("gender"));
                            MainApp.facebookUserInfo.setMiddleName(jsonResponse.optString("middle_name"));
                            MainApp.facebookUserInfo.setLink(jsonResponse.optString("link"));
                        }

                        //Se invoca a la aplicación para cerrar esta pantalla después de 
                        //completarse la operación
                        UiApplication.getUiApplication().invokeLater(new Runnable() {

                            public void run() {
                                UiApplication.getUiApplication().getActiveScreen().close();

                            }
                        });
                    }
                }
             }
        };
        _browserField.addListener(browserListener);
        add(_browserField);
        UiApplication.getUiApplication().pushScreen(loadingScreen);
    }

    private class LoadingScreen extends PopupScreen{
        private AnimatedGIFField _loader;
        public LoadingScreen(){
            super(new VerticalFieldManager());
            GIFEncodedImage ourAnimation = (GIFEncodedImage) GIFEncodedImage.getEncodedImageResource("ajax-loader (7).gif");
            _loader = new AnimatedGIFField(ourAnimation, Field.FIELD_HCENTER);
            this.add(_loader);
        }

        public boolean onClose() {
            setDirty(false);
            return super.onClose();
        }
    }


    /**
     * Extra un valor especificado del URL
     * 
     * @param url 
                URL del cuál se va a extraer un valor
     * @param element
                Elemento que se desea obtener
     * @return
     */
    private String getElement(String url, String element)
    {
        int startIndex = url.indexOf(element);

        if (startIndex > -1) {
            int stopIndex = url.length();

            if (url.indexOf('&', startIndex) > -1) {
                stopIndex = url.indexOf('&', startIndex);
            } else if (url.indexOf(';', startIndex) > -1) {
                stopIndex = url.indexOf(';', startIndex);
            }

            element = url.substring(url.indexOf('=', startIndex) + 1, stopIndex);


            return element;
        }

        return "";
    }   
}

At a glance 4 things look odd to me:

1). you are settings listener AFTER you have requested the content (so it may happen the page can be loaded BEFORE the listener will be able to react).

2). loadingScreen.onClose(); - what do you expect this will do?

3). UiApplication.getUiApplication().getActiveScreen().close(); - are you really sure which screen you are closing? Looks like your are an incurable optimist.

4). I've never used BrowserFieldListener, so this point is just a guess: BrowserFieldListener has other callbacks including those for failures. So what if BrowserField.requestContent(String url) fails (there could be a dozen potential reasons for that) - will that end up calling the same callback you are using?

UPDATE:

I guess the problem is all what you're doing happens sequentially on a UI-thread. So you push a progress screen, do sthm useful, then close the progress - all this happens on a UI-thread sequentially. In this case you do not give the UI-framework a chance to actually display/draw the progress screen. To draw a screen the UI-thread needs some FREE cpu time. When UI-thread comes to the point where it could start drawing the progress screen it finds there is no need to do it already, because the progress screen has been closed.

A simple (and dirty) workaround would be to call UiApplication.repaint() right after you push the progress screen. This method does the following:

Repaints entire display.

Invoke this method to repaint the entire display. It invalidates, and then paints, each screen on the display stack.