iphone - 在 iOS 中清除内存警告的 url 缓存

Question

当收到内存警告时，清除共享的 NSURLCache 是个好习惯吗？像这样:

- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application {
    [[NSURLCache sharedURLCache] removeAllCachedResponses];
}

我假设这也会不必要地清除磁盘缓存是否正确？

如果是这样，是否可以只清除内存缓存？

Answer 1

当出现内存警告时，您只需要清除内存缓存而不是磁盘缓存。 removeAllCachedResponses 的问题在于它会清除两者。从我的测试来看，这似乎只清除了内存缓存。

- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application {

    NSURLCache * const urlCache = [NSURLCache sharedURLCache];
    const NSUInteger memoryCapacity = urlCache.memoryCapacity;
    urlCache.memoryCapacity = 0;
    urlCache.memoryCapacity = memoryCapacity;
}

我唯一关心的是线程问题。 this底部有脚注文章。

There are a lot of recommendations on StackOverflow about purging the NSURLCache by recreating it, however, we’ve seen this lead to occasional crashes when requests occur on another thread while the cache is being recreated. Our advice is therefore to create the cache once when the app starts and purge it when appropriate.

上述解决方案不会重新创建缓存，但它可能仍然会遇到同样的问题，我还没有对此进行广泛的测试。