如何在黑莓BrowserField缓存 [英] How to cache in a Blackberry BrowserField
问题描述
我创建的BlackBerry应用程序来显示某网站的全屏Web视图。我有一个显示正常，但在页面页面导航比原生浏览器慢工作browserfield。该browserfield似乎不具有内置的缓存，使负载的时间会很慢。当我添加以下code到管理网站不能正常显示缓存。
I am creating a Blackberry application to display a full screen web view of a certain site. I have a working browserfield that displays properly but navigation from page to page is slower than that of the native browser. The browserfield does not seem to have a built in cache causing the load time to be slow. When I add the following code to manage the cache the site no longer displays properly.
BrowserFieldScreen.java：
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：
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：
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：
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：
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;
}
}
任何帮助，可以朝这个是给将大大AP preciated。这确实有我难住了。谢谢你。
Any help that can be giving towards this will be greatly appreciated. This really has me stumped. Thanks.
更新：它看起来像只缓存工作在黑莓库的一定水平。我加入的逻辑来检查当前软件水平，如果它是由设备的当前软件层面支持打开缓存。这为我提供了一个很好的变通，但我还是想知道如果有一个缓存与所有设备的工作更好的办法。
UPDATE: It looks like the caching only works at a certain level of the Blackberry libraries. I have added logic to check the current Software level and turn on the caching if it is supported by the device's current software level. This provides me with a good work around, but i would still like to know if there is a better way for the caching to work with all devices.
更新2 基于评论：站点不再正常显示属于网站显示不正确的布局，图像和文字。它基本上得白色背景链接和文本显示为项目符号列表，所有格式中删除。
UPDATE 2 Based on comments: The site no longer displaying properly pertains to site not displaying the proper layout, images and text. It basically give a white background with links and text displaying as a bulleted list, all formatting removed.
推荐答案
我一直在找你的code，我发现的唯一的事有不对的地方，是您完全无视的可能性 response.getLength（）; 返回小于0（ CacheManagerImpl.createCache（））。虽然这并不在stackoverflow.com页面发生在我身上，有的页面使用传输编码：分块，这意味着内容长度不是present。这是，然而，井处理，并且不应该导致缓存失败（它只会是不太有效）。
I've been looking at your code, and the only thing I've found there's wrong with it, is you are completely ignoring the possibility of response.getLength(); returning less than zero (in CacheManagerImpl.createCache()). Although this didn't happen to me at the stackoverflow.com page, some pages use Transfer-Encoding: chunked, which means Content-Length is not present. This is, however, well handled, and should not cause the cache to fail (it would only be less effective).
我建议在测试较小的问题你code，一步一个脚印的时间。首先，创建缓存页面，只包含一些文字（如你好）没有任何HTML标签。这应该工作pretty好，如果没有，它不应该是很难确定的数据迷路。或尝试手动创建不会过期，包含无（外部）样式表，也没有图像的网页缓存项，看看它甚至有可能将它传递给 BrowserField 的方式你做吧。然后建立上，添加图像，添加一个样式表，所以你能垄断的问题。
I suggest testing your code on smaller problems, one step at a time. First, create cacheable page that only contains some text (like "hello") without any HTML tags. That should work pretty well, and in case it does not, it shouldn't be hard to determine where the data are getting lost. Or try to manually create cache item that does not expire and contains a webpage with no (external) stylesheet nor images, and see if it's even possible to pass it to BrowserField the way you do it. Then build on, add an image, add a style sheet so you can corner the problem.
在code写得很漂亮，但在这一点，就不可能帮你，因为有在code没有明显的缺陷和你不解释自己很好，目前尚不清楚错误是如何体现的，如果是每次或随机的，...如果我有一个黑莓设备，我大概可以尝试运行code代表我自己，但我没有。
The code is written very nicely, but at this point, it is not possible to help you because there are no evident flaws in the code and you are not explaining yourself very well, it is not clear how the error manifests itself, if it is every time or random, ... If I had a Blackberry device, I could probably try running the code for myself, but i don't.
这篇关于如何在黑莓BrowserField缓存的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
