Memory leak with UIWebView

Question

My project is a hybrid static lib for showing a UIWebView with some JS to control the logic. When I use 64bit and run demo on iOS 8/iPhone 6, the memory keeps going to 30M or more!

1. When I use generation in instrument, the increased memory usage is almost all from webcore; does it means there are leaks in JS code? I can't find a leak when I use Safari to run similar JS directly.

2. When I release the UIWebView, the memory is still not freed; I tested with instrument allocation. There are some webcore and (non - object) still in memory, what can I do to release them?

   • 0JavaScriptCore WTF::MallocHook::recordAllocation(void*, unsigned long)
   • 1 JavaScriptCore WTF::fastMalloc(unsigned long)
   • 2 WebCore WebCore::SharedBuffer::buffer() const
   • 3 WebCore WebCore::SharedBuffer::data() const
   • 4 WebCore WebCore::ResourceLoader::didReceiveDataOrBuffer(char const*, unsigned int, WTF::PassRefPtr, long long, WebCore::DataPayloadType)
   • 5 WebCore WebCore::SubresourceLoader::didReceiveDataOrBuffer(char const*, int, WTF::PassRefPtr, long long, WebCore::DataPayloadType)
   • 6 WebCore WebCore::SubresourceLoader::didReceiveBuffer(WTF::PassRefPtr, long long, WebCore::DataPayloadType)
   • 7 WebCore WebCore::ResourceLoader::didReceiveBuffer(WebCore::ResourceHandle*, WTF::PassRefPtr, int)
   • 8 WebCore WebCore::SynchronousResourceHandleCFURLConnectionDelegate::didReceiveDataArray(__CFArray const*)

I use the following code.

-(void)createUIWebview{
[self.webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:serviceUrl]]];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
[[NSUserDefaults standardUserDefaults] setInteger:0 forKey:@"WebKitCacheModelPreferenceKey"];
}

-(void)dealloc{
if (_webView.isLoading){
    [_webView stopLoading];
}
[_webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"about:blank"]]];
_webView.delegate=nil;
[_webView removeFromSuperview];
[_webView release];
_webView = nil;
}

I have researched the following links, but they don't seem to solve my problem. Is UIWebview still leaking in iOS 8? And the problem seems not so obvious when I use iOS 6 in iPhone4.

Whats the proper way to release a UIWebView?

iOS 8 UIWebView memory management

UIWebView leaks, JS Garbage Collector & WebCore VMs

Release memory/cookie/cache from UIWebView once closed

Answer 1

I was having the same problem and switched to the new WKWebView and it immediately solved all of the memory leak issues I was seeing. WKWebView shares many of the same call names from UIWebView so all I had to do on my project is switch over all my `UIWebView' objects to 'WKWebView' and the memory leaks went away.

Remember to import the WebKit into your project and know that is is only available on iOS8.

Apple Documentation