Estou criando um aplicativo Blackberry para exibir uma exibição na Web em tela cheia de um determinado site. Eu tenho um campo de navegador funcionando que é exibido corretamente, mas a navegação de página para página é mais lenta que a do navegador nativo. O campo do navegador não parece ter um cache interno, o que torna o tempo de carregamento lento. Quando adiciono o código a seguir para gerenciar o cache, o site não é mais exibido corretament

BrowserFieldScreen.java:

import net.rim.device.api.browser.field2.*;
import net.rim.device.api.script.ScriptEngine;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import org.w3c.dom.Document;

class BrowserFieldScreen extends MainScreen
{
    BrowserField browserField;
    LoadingScreen load = new LoadingScreen();;

    public BrowserFieldScreen()
    {   
        browserField = new BrowserField();
        browserField.getConfig().setProperty(
            BrowserFieldConfig.JAVASCRIPT_ENABLED, 
            Boolean.TRUE);
        browserField.getConfig().setProperty(
            BrowserFieldConfig.NAVIGATION_MODE, 
            BrowserFieldConfig.NAVIGATION_MODE_POINTER);
        browserField.getConfig().setProperty(
            BrowserFieldConfig.CONTROLLER, 
            new CacheProtocolController(browserField));

        browserField.requestContent("http://www.stackoverflow.com");
        add(browserField);
    }
}

CacheProtocolController.java:

import javax.microedition.io.HttpConnection;
import javax.microedition.io.InputConnection;

import net.rim.device.api.browser.field2.BrowserField;
import net.rim.device.api.browser.field2.BrowserFieldRequest;
import net.rim.device.api.browser.field2.ProtocolController;

public class CacheProtocolController extends ProtocolController{

    // The BrowserField instance
    private BrowserField browserField;

    // CacheManager will take care of cached resources 
    private CacheManager cacheManager;

    public CacheProtocolController(BrowserField browserField) {
        super(browserField);
        this.browserField = browserField;
    }

    private CacheManager getCacheManager() {
        if ( cacheManager == null ) {
            cacheManager = new CacheManagerImpl();
        }
        return cacheManager;
    }

    /**
     * Handle navigation requests (e.g., link clicks)
     */
    public void handleNavigationRequest(BrowserFieldRequest request) 
        throws Exception 
    {
        InputConnection ic = handleResourceRequest(request);
        browserField.displayContent(ic, request.getURL());
    }

    /**
     * Handle resource request 
     * (e.g., images, external css/javascript resources)
     */
    public InputConnection handleResourceRequest(BrowserFieldRequest request) 
        throws Exception 
    {
        // if requested resource is cacheable (e.g., an "http" resource), 
            // use the cache
        if (getCacheManager() != null 
            && getCacheManager().isRequestCacheable(request)) 
            {
                InputConnection ic = null;
                // if requested resource is cached, retrieve it from cache
                if (getCacheManager().hasCache(request.getURL()) 
                    && !getCacheManager().hasCacheExpired(request.getURL())) 
                {
                    ic = getCacheManager().getCache(request.getURL());
                }
                // if requested resource is not cached yet, cache it
                else 
                {
                ic = super.handleResourceRequest(request);
                    if (ic instanceof HttpConnection) 
                    {
                        HttpConnection response = (HttpConnection) ic;
                        if (getCacheManager().isResponseCacheable(response)) 
                        {
                        ic = getCacheManager().createCache(request.getURL(), 
                             response);
                        }
                }
            }
            return ic;
        }
        // if requested resource is not cacheable, load it as usual
        return super.handleResourceRequest(request);
    }

}

CacheManager.java:

import javax.microedition.io.HttpConnection;
import javax.microedition.io.InputConnection;

import net.rim.device.api.browser.field2.BrowserFieldRequest;

public interface CacheManager {
    public boolean isRequestCacheable(BrowserFieldRequest request);
    public boolean isResponseCacheable(HttpConnection response);
    public boolean hasCache(String url);
    public boolean hasCacheExpired(String url);
    public InputConnection getCache(String url);
    public InputConnection createCache(String url, HttpConnection response);
    public void clearCache(String url);
}

CacheManagerImpl.java:

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.Hashtable;

import javax.microedition.io.HttpConnection;
import javax.microedition.io.InputConnection;

import net.rim.device.api.browser.field2.BrowserFieldRequest;
import net.rim.device.api.browser.field2.BrowserFieldResponse;
import net.rim.device.api.io.http.HttpHeaders;


public class CacheManagerImpl implements CacheManager {

    private static final int MAX_STANDARD_CACHE_AGE = 2592000;
    private Hashtable cacheTable;

    public CacheManagerImpl() {
        cacheTable = new Hashtable();
    }

    public boolean isRequestCacheable(BrowserFieldRequest request) {
        // Only HTTP requests are cacheable
        if (!request.getProtocol().equals("http")) {
            return false;
        }

        // Don't cache the request whose method is not "GET".
        if (request instanceof HttpConnection) {
            if (!((HttpConnection) request).getRequestMethod().equals("GET")) 
            {
                return false;
            }
        }

        // Don't cache the request with post data.
        if (request.getPostData() != null) {
                return false;
        }

        // Don't cache authentication request.
        if (request.getHeaders().getPropertyValue("Authorization") != null) {
            return false;
        }        

        return true;        
    }

    public boolean isResponseCacheable(HttpConnection response) {
        try {
            if (response.getResponseCode() != 200) {
                return false;
            }
        } catch (IOException ioe) {
            return false;
        }

        if (!response.getRequestMethod().equals("GET")) {
            return false;
        }

        if (containsPragmaNoCache(response)) {
            return false;
        }

        if (isExpired(response)) {
            return false;
        }

        if (containsCacheControlNoCache(response)) {
            return false;
        }

        if ( response.getLength() <= 0 ) {
            return false;
        }

        // additional checks can be implemented here to inspect
        // the HTTP cache-related headers of the response object

        return true;
    }

    private boolean isExpired(HttpConnection response) {
        try 
        {
            // getExpiration() returns 0 if not known
            long expires = response.getExpiration(); 
            if (expires > 0 && expires <= (new Date()).getTime()) {
                return true;
            }    
            return false;
        } catch (IOException ioe) {
            return true;
        }
    }

    private boolean containsPragmaNoCache(HttpConnection response) {
        try 
        {
            if (response.getHeaderField("pragma") != null 
                && response.getHeaderField("pragma")
                           .toLowerCase()
                           .indexOf("no-cache") >= 0) 
            {
                return true;
            } 

            return false;
        } catch (IOException ioe) {
            return true;
        }
    }

    private boolean containsCacheControlNoCache(HttpConnection response) {
        try {
            String cacheControl = response.getHeaderField("cache-control");
            if (cacheControl != null) {
                cacheControl = removeSpace(cacheControl.toLowerCase());
                if (cacheControl.indexOf("no-cache") >= 0 
                    || cacheControl.indexOf("no-store") >= 0 
                    || cacheControl.indexOf("private") >= 0 
                    || cacheControl.indexOf("max-age=0") >= 0) {
                    return true;        
                }

                long maxAge = parseMaxAge(cacheControl);
                if (maxAge > 0 && response.getDate() > 0) {
                    long date = response.getDate();
                    long now = (new Date()).getTime();                    
                    if (now > date + maxAge) {
                        // Already expired
                        return true;
                    }
                }
            } 

            return false;
        } catch (IOException ioe) {
            return true;
        }
    }    

    public InputConnection createCache(String url, HttpConnection response) {

        byte[] data = null;
        InputStream is = null;
        try {
            // Read data
            int len = (int) response.getLength();
            if (len > 0) {
                is = response.openInputStream();
                int actual = 0;
                int bytesread = 0 ;
                data = new byte[len];
                while ((bytesread != len) && (actual != -1)) {
                    actual = is.read(data, bytesread, len - bytesread);
                    bytesread += actual;
                }
            }       
        } catch (IOException ioe) {
            data = null;
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException ioe) {
                }
            }
            if (response != null) {
                try {
                    response.close();
                } catch (IOException ioe) {
                }
            } 
        }

        if (data == null) {
            return null;
        } 

        // Calculate expires
        long expires = calculateCacheExpires(response);

        // Copy headers
        HttpHeaders headers = copyResponseHeaders(response);

        // add item to cache
        cacheTable.put(url, new CacheItem(url, expires, data, headers));

        return new BrowserFieldResponse(url, data, headers);
    }

    private long calculateCacheExpires(HttpConnection response) {
        long date = 0;
        try {
            date = response.getDate();
        } catch (IOException ioe) {
        }

        if (date == 0) {
            date = (new Date()).getTime();
        }

        long expires = getResponseExpires(response);

        // If an expire date has not been specified assumes the maximum time
        if ( expires == 0 ) {
            return date + (MAX_STANDARD_CACHE_AGE * 1000L);
        }

        return expires;
    }

    private long getResponseExpires(HttpConnection response) {
        try {
            // Calculate expires from "expires"
            long expires = response.getExpiration();
            if (expires > 0) {
                return expires;
            }

            // Calculate expires from "max-age" and "date"
            if (response.getHeaderField("cache-control") != null) {
                String cacheControl = removeSpace(response
                                               .getHeaderField("cache-control")
                                               .toLowerCase());
                long maxAge = parseMaxAge(cacheControl);
                long date = response.getDate();

                if (maxAge > 0 && date > 0) {
                    return (date + maxAge);
                }
            }
        } catch (IOException ioe) {
        }

        return 0;
    }

    private long parseMaxAge(String cacheControl) {
        if (cacheControl == null) {
            return 0;
        }

        long maxAge = 0;
        if (cacheControl.indexOf("max-age=") >= 0) {
            int maxAgeStart = cacheControl.indexOf("max-age=") + 8;
            int maxAgeEnd = cacheControl.indexOf(',', maxAgeStart);
            if (maxAgeEnd < 0) {
                maxAgeEnd = cacheControl.length();
            }

            try {
                maxAge = Long.parseLong(cacheControl.substring(maxAgeStart,
                                                               maxAgeEnd));
            } catch (NumberFormatException nfe) {
            }
        }

                // Multiply maxAge by 1000 to convert seconds to milliseconds
                maxAge *= 1000L;
        return maxAge;
    }

    private static String removeSpace(String s) {
        StringBuffer result= new StringBuffer();
        int count = s.length();
        for (int i = 0; i < count; i++) {
            char c = s.charAt(i);
            if (c != ' ') {
                result.append(c);
            }
        }

        return result.toString();
    }

    private HttpHeaders copyResponseHeaders(HttpConnection response) {
        HttpHeaders headers = new HttpHeaders();
        try {
            int index = 0;
            while (response.getHeaderFieldKey(index) != null) {
                headers.addProperty(response.getHeaderFieldKey(index),
                                    response.getHeaderField(index));
                index++;
            }
        } catch (IOException ioe) {
        }

        return headers;
    }    

    public boolean hasCache(String url) {
        return cacheTable.containsKey(url);
    }

    public boolean hasCacheExpired(String url) {
        Object o = cacheTable.get(url);

        if (o instanceof CacheItem) {
            CacheItem ci = (CacheItem) o;
            long date = (new Date()).getTime();
            if (ci.getExpires() > date) {
                return false;
            } else {
                // Remove the expired cache item
                clearCache(url);
            }
        }

        return true;
    }

    public void clearCache(String url) {
        cacheTable.remove(url);
    }    

    public InputConnection getCache(String url) {
        Object o = cacheTable.get(url);        
        if (o instanceof CacheItem) {
            CacheItem ci = (CacheItem) o;
            return new BrowserFieldResponse(url, 
                                            ci.getData(), 
                                            ci.getHttpHeaders());
        }        
        return null;
    }
}

CacheItem.java:

import net.rim.device.api.io.http.HttpHeaders;

public class CacheItem {

    private String  url;    
    private long    expires;    
    private byte[] data;
    private HttpHeaders httpHeaders;

    public CacheItem(String url, 
                     long expires, 
                     byte[] data, 
                     HttpHeaders httpHeaders)
    {
        this.url = url;
        this.expires = expires;
        this.data = data;
        this.httpHeaders = httpHeaders;
    }

    public String getUrl() {
        return url;
    }

    public long getExpires() {
        return expires;
    }

    public byte[] getData() {
        return data;
    }

    public HttpHeaders getHttpHeaders() {
        return httpHeaders;
    }
}

Qualquer ajuda que possa estar dando para isso será muito apreciada. Isso realmente me deixou perplexo. Obrigado

ATUALIZAR Parece que o cache só funciona em um determinado nível das bibliotecas do Blackberry. Eu adicionei lógica para verificar o nível atual do software e ativar o armazenamento em cache, se for suportado pelo nível atual do software do dispositivo. Isso me fornece uma boa solução, mas eu ainda gostaria de saber se existe uma maneira melhor de o cache funcionar com todos os dispositivos.

UPDATE 2 Com base nos comentários: o site não exibe mais corretamente pertence ao site que não exibe o layout, imagens e texto adequados. Basicamente, fornece um plano de fundo branco com links e texto exibidos como uma lista com marcadores, toda a formatação removida.