UIWebView的离线缓存

实际上,UIWebView自己是有缓存的,但容量有限,清理时间我们也不好掌握,那它是用什么做的缓存呢?是NSURLCache。看到它有几个方法:

+ (void)setSharedURLCache:(NSURLCache *)cache;

- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request;

- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest*)request;

太好了,我们只要写一个子类继承NSURLCache,实现后两个方法,再让这个子类对象成为sharedURLCache,就可以操控webView的请求和缓存了。抛个砖吧:

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- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {
                                                                                                                                                                                                                          
    NSString *pathString = [[request URL] absoluteString];
                                                                                                                                                                                                                          
    if (![pathString hasSuffix:@".jpg"]) {
        return [super cachedResponseForRequest:request];
    }
                                                                                                                                                                                                                          
    if ([[MYURLCache sharedCache] hasDataForURL:pathString]) {
        NSData *data = [[MYURLCache sharedCache] dataForURL:pathString];
        NSURLResponse *response = [[[NSURLResponse alloc] initWithURL:[request URL]
                                                             MIMEType:@"image/jpg"
                                                expectedContentLength:[data length]
                                                     textEncodingName:nil] autorelease];
        return [[[NSCachedURLResponse alloc] initWithResponse:response data:data] autorelease];       
    }
    return [super cachedResponseForRequest:request];
}
                                                                                                                                                                                                                      
- (void)storeCachedResponse:(NSCachedURLResponse *)cachedResponse forRequest:(NSURLRequest *)request {
    NSString *pathString = [[request URL] absoluteString];
    if (![pathString hasSuffix:@".jpg"]) {
        [super storeCachedResponse:cachedResponse forRequest:request];
        return;
    }
                                                                                                                                                                                                                          
    [[MYURLCache sharedCache] storeData:cachedResponse.data forURL:pathString];
}

上面的代码是专门用来搞定webView中的jpg图片的,其中MYURLCache提供了把data读、写入文件的功能,这个不是本文的重点,请各位自己实现吧。

在程序启动的时候,加入以下代码:

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MYURLCache *cache = [[MYURLCache alloc] init];
[NSURLCache setSharedURLCache:cache];

OK,搞定了,试试webView加载图片吧~

posted on 2015-08-27 14:30  yucaijiang  阅读(299)  评论(0编辑  收藏  举报

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