[ios] Clearing UIWebview cache

I have used UIWebview to load a web page using loadRequest: method, when I leave that scene I call [self.webView stopLoading]; and release the webView.

In activity monitor on first launch i have seen that the real memory increased by 4MB, and on multiple launches/loading the real memory doesn't increase. It is increasing only once.

I have checked the retain count of webview. It is proper i.e., 0. I think UIWebView is caching some data. How do I avoid caching or remove cached data? Or is there another reason for this?

My educated guess is that the memory use you are seeing is not from the page content, but rather from loading UIWebView and all of it's supporting WebKit libraries. I love the UIWebView control, but it is a 'heavy' control that pulls in a very large block of code.

This code is a large sub-set of the iOS Safari browser, and likely initializes a large body of static structures.

You can disable the caching by doing the following:

NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:nil];
[NSURLCache setSharedURLCache:sharedCache];
[sharedCache release];

ARC:

NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:nil];
[NSURLCache setSharedURLCache:sharedCache];

For swift 2.0:

let cacheSizeMemory = 4*1024*1024; // 4MB
let cacheSizeDisk = 32*1024*1024; // 32MB
let sharedCache = NSURLCache(memoryCapacity: cacheSizeMemory, diskCapacity: cacheSizeDisk, diskPath: "nsurlcache")
NSURLCache.setSharedURLCache(sharedCache)

After various attempt, only this works well for me (under ios 8):

NSURLCache *cache = [[NSURLCache alloc] initWithMemoryCapacity:1 diskCapacity:1 diskPath:nil];
[NSURLCache setSharedURLCache:cache];

Don't disable caching completely, it'll hurt your app performance and it's unnecessary. The important thing is to explicitly configure the cache at app startup and purge it when necessary.

So in application:DidFinishLaunchingWithOptions: configure the cache limits as follows:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{   
    int cacheSizeMemory = 4*1024*1024; // 4MB
    int cacheSizeDisk = 32*1024*1024; // 32MB
    NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:cacheSizeMemory diskCapacity:cacheSizeDisk diskPath:@"nsurlcache"];
    [NSURLCache setSharedURLCache:sharedCache];

    // ... other launching code
}

Once you have it properly configured, then when you need to purge the cache (for example in applicationDidReceiveMemoryWarning or when you close a UIWebView) just do:

[[NSURLCache sharedURLCache] removeAllCachedResponses];

and you'll see the memory is recovered. I blogged about this issue here: http://twobitlabs.com/2012/01/ios-ipad-iphone-nsurlcache-uiwebview-memory-utilization/

I could not change the code, so I needed command line for testing purpose and figured this could help someone:

Application specific caches are stored in ~/Library/Caches/<bundle-identifier-of-your-app>, so simply remove as below and re-open your application

rm -rf ~/Library/Caches/com.mycompany.appname/

I am loading html pages from Documents and if they have the same name of css file UIWebView it seem it does not throw the previous css rules. Maybe because they have the same URL or something.

I tried this:

NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:nil];
[NSURLCache setSharedURLCache:sharedCache];
[sharedCache release];

I tried this :

[[NSURLCache sharedURLCache] removeAllCachedResponses];

I am loading the initial page with:

NSURLRequest *appReq = [NSURLRequest requestWithURL:appURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:20.0];

It refuses to throw its cached data! Frustrating!

I am doing this inside a PhoneGap (Cordova) application. I have not tried it in isolated UIWebView.

Update1: I have found this.
Changing the html files, though seems very messy.

Swift 3.

// Remove all cache 
URLCache.shared.removeAllCachedResponses()

// Delete any associated cookies     
if let cookies = HTTPCookieStorage.shared.cookies {
    for cookie in cookies {
        HTTPCookieStorage.shared.deleteCookie(cookie)
    }
}