禁用UIWebView DiskImageCache [英] Disable UIWebView DiskImageCache

问题描述

当加载包含图像的文档（例如 Microsoft Word docx 文件）时，UIWebView会在收到内存警告时始终缓存图像，而不考虑缓存策略。

When loading documents that contain images (such as a Microsoft Word docx file), the UIWebView will always cache the images when it receives a memory warning regardless of the cache policy.

下面是一个示例代码段：

Following, there's a sample code snippet:

NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:1024 * 1024
                                              diskCapacity:0
                                              diskPath:[NSTemporaryDirectory() stringByAppendingPathComponent:@"URLCache"]];
[NSURLCache setSharedURLCache:sharedCache];

NSURLRequest* req = [NSURLRequest requestWithURL:
                    [NSURL URLWithString:@"http://www.its.swinburne.edu.au/about/projects/templates/TechnicalSpecificationTemplatev1.1-[ProjectName]-[ver]-[YYYYMMDD].docx"] 
                    cachePolicy:NSURLRequestReloadIgnoringCacheData 
                    timeoutInterval:10];

在这种情况下，如果发生内存警告，则会在 tmp中创建一个新文件夹应用程序的目录，通常名为 DiskImageCache-random_suffix ，打开的文档中的所有映像都保存在此处。

Under these circumstances, if a memory warning occurs, a new folder is created in the tmp directory of the app, usually named DiskImageCache-random_suffix and all the images in the opened document are saved here.

UIWebView 加载新请求，如果我打电话

After the UIWebView loads a new request, if I call

[sharedCache removeAllCachedResponses];

这些临时图像已删除。

防止缓存图像的唯一方法是调用

The only way to prevent caching the images is to call

[NSClassFromString(@"WebCache") performSelector:@selector(setDisabled:) withObject:[NSNumber numberWithBool:YES]];

但这意味着使用私有API。

but this means using private API.

是否有 Apple友好方式来实现这一目标？

Is there an "Apple friendly" way to achieve this ?

推荐答案

我在研究了WebKit中未记录后才发现了这一点。首选项。使用以下设置，可以在应用程序的整个生命周期中禁用DiskImageCache：

I figured it out after looking into the WebKit "undocumented" preferences. With the following setting, it is possible to disable DiskImageCache for the entire lifetime of the application:

[[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"WebKitDiskImageCacheEnabled"];
[[NSUserDefaults standardUserDefaults] synchronize];

这篇关于禁用UIWebView DiskImageCache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！