Freeing iOS UIWebView resources after usage

Question

Our app's home screen (and therefore the first seen by all users) has several sections, most of which contain diferent webviews the user may want to open. Doing so increases memory usage from barely 26MB to up to 85MB or even more (after opening all diferent webviews).

The problem we found is that, once they're closed, all web page resources seem to be kept at memory (used memory barely decreases a couple of MB perhaps).

I would like to free the resources the webview had to open because, later on, there's a very demanding section of our app which needs a lot of memory and completely crashes the app if you happen to have been browsing through several of those webviews before.

I have found several options on the internet to try but none of them have worked so far. Things such as:

// Try to clean used webview

[self.webView loadHTMLString:@"" baseURL:nil];
[self.webView stopLoading];
self.webView.delegate = nil;
[self.webView removeFromSuperview];
self.webView = nil;

They've made absolutely almost no effect on memory usage. Is there anything I'm missing here? I already double checked that I have no leaks that would keep the WebView opened, I'm already freeing the only reference to it that I have (self.webView = nil;)

Edit: I just created a project from scratch, added a webview and a button which loads a different web every time I click it, which in turn increases memory usage. I also added a button that will destroy the webview when clicked and, guess what, memory stays the same, like it's effectively not releasing any resources.

Answer 1

It's been several months since I asked this question and it seems no one knows any work around, so I'm just answering myself to give it some closure and, sadly, bad news to whoever is having this same issue.

We kept trying to fight this issue for several days and, after talking to some people who somehow hinted us that we had nothing to do about it (it's just a different process taking care of everything to which we have no access), we decided to restrict the webview access to custom made pages.

For example, we had a news sections which opened webs on the internet. What we ended up doing was open custom-made web pages which contained the title, body and an image related to the news (which still adds to resource memory usage, but we managed to keep it in a contained small format which would need thousands of news to be opened to be of any danger). I know, not ideal.

I'd still love to see some constructive answers to this question, whether it's a solution, a workaround, or any idea that can help future users with this same issue have clues on how to deal with it.

Answer 2

you should read this article from Jason Baker,

http://www.codercowboy.com/code-uiwebview-memory-leak-prevention/

He has created a category which really helped me to redue memory footprint of UIWebView.

you just have to call two lines after adding category

-(void) dealloc
{

    [self.webview cleanForDealloc];
    self.webview = nil;
    [super dealloc];

}

Answer 3

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    categoryWebView.stopLoading()
    categoryWebView.removeFromSuperview()
    categoryWebView = nil

    URLCache.shared.removeAllCachedResponses()
    URLCache.shared.diskCapacity = 0
    URLCache.shared.memoryCapacity = 0
    if let cookies = HTTPCookieStorage.shared.cookies {
        for cookie in cookies {
            HTTPCookieStorage.shared.deleteCookie(cookie)
        }
    }
}