我正在我的 iPhone/iPad 应用程序中下载图像 - 因为它们大部分时间都保持不变，所以我想将它们缓存在磁盘上:

ASIDownloadCache *cache = [ASIDownloadCache sharedCache];
[asiRequest setDownloadCache:cache];
[asiRequest setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
[asiRequest setCachePolicy:ASIOnlyLoadIfNotCachedCachePolicy];
[asiRequest setSecondsToCache:60*60*24*30]; // Cache for 30 days
[asiRequest setDelegate:self]; // A delegate must be specified
[asiRequest setDidFinishSelector:@selector(requestFinished:)];
[asiRequest startAsynchronous];

在我的requestFinished-method中，识别出缓存是成功的，但是我的request-object中的数据是空的；我错过了什么？

- (void) requestFinished:(ASIHTTPRequest *)request {
   if ([request didUseCachedResponse]) {
       NSLog(@"cache, size: %i", [[request responseData] length]); // is always zero
       [self buildImageWithData:[request responseData]];
   }
   [...];
}

非常感谢!

编辑 1: 我的完整代码不起作用:第一次，我收到“未缓存”语句，从那时起，“缓存，大小:0”...我有不知道为什么 :(

- (void)viewDidLoad {
    [super viewDidLoad];

    for (int i = 0; i < 10; i++) {
        asiRequest = [[ASIHTTPRequest alloc] initWithURL:[NSURL URLWithString:@"http://www.myimageserver.com/myimage.jpg"]];

        ASIDownloadCache *cache = [ASIDownloadCache sharedCache];
        [asiRequest setDownloadCache:cache];
        [asiRequest setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
        [asiRequest setCachePolicy:ASIOnlyLoadIfNotCachedCachePolicy];
        [asiRequest setSecondsToCache:60*60*24*30]; // Cache for 30 days
        [asiRequest setDelegate:self]; // A delegate must be specified
        [asiRequest setDidFinishSelector:@selector(requestFinished:)];
        [asiRequest startAsynchronous];
    }
}

- (void) request:(ASIHTTPRequest *)request didReceiveResponseHeaders:(NSDictionary *)responseHeaders {
    self.imageDataLoadedFromURL = [NSMutableData data];
}

- (void) request:(ASIHTTPRequest *)request didReceiveData:(NSData *)data {
    [imageDataLoadedFromURL appendData:data];
}

- (void) requestFinished:(ASIHTTPRequest *)request {
    if ([request didUseCachedResponse]) {
        NSLog(@"cache, size: %i", [[request responseData] length]); // is always zero
    } else {
        NSLog(@"not cached");
    }
}

编辑 2: 缓存似乎已经包含 0 字节图像；所以这不是从缓存中读取而是写入缓存的问题......

编辑 3: 您可以从 http://tinyurl.com/68wuwj2 下载小型测试项目。

最佳答案

您能否设置断点、清除缓存(例如，删除您的应用程序)然后单步执行这段代码(ASIDownloadCache.m，第 184 行，方法 storeResponseForRequest):

if ([request responseData]) {
    [[request responseData] writeToFile:dataPath atomically:NO];
} else if ([request downloadDestinationPath] && ![[request downloadDestinationPath] isEqualToString:dataPath]) {
    NSError *error = nil;
    [[[[NSFileManager alloc] init] autorelease] copyItemAtPath:[request downloadDestinationPath] toPath:dataPath error:&error];
}

检查遵循的路径，并检查request.responseData的大小。

** 编辑 **

您的问题是您对 didReceiveData 的使用:

- (void) request:(ASIHTTPRequest *)request didReceiveData:(NSData *)data {
    [imageDataLoadedFromURL appendData:data];
}

引用asi http请求文档:

If you need to process the response as it comes in (for example, you want to use a streaming parser to parse the response while it is still being downloaded), have your delegate implement request:didReceiveData: (see ASIHTTPRequestDelegate.h). Note that when you do this, ASIHTTPRequest will not populate responseData or write the response to downloadDestinationPath - you must store the response yourself if you need to.

最后一句话似乎也适用于缓存数据。

这可能是 asihttprequest 中的一个错误，实际上它不应该在这种情况下将数据写入缓存，或者应该确保它正在写入有效数据——目前看起来它写入了一个无效的缓存条目。您是否需要在数据到达时对其进行处理？如果不只是删除“didReceiveBytes”并仅使用 requestFinished 中的 request.responseData 中提供的数据。

关于ios - ASIHTTPRequest - 来自缓存的数据始终为空，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6478145/