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POPreventing UIWebView to allocate memory indefinitely (NSURLCache apparently not working)
 

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    <p>I have been trying to understand how the UIWebView cache works. Since my goal is <strong>to be able to manage the memory allocated by the UIWebView</strong> (at least, as much as possible), to avoid memory raising indefinitely and the App getting killed because of this.</p> <p>After <a href="https://stackoverflow.com/questions/9744644/uiwebview-without-cache">reading</a> <a href="https://stackoverflow.com/questions/2090286/uiwebview-and-nsurlcache-have-a-troubled-relationship">other</a> <a href="https://stackoverflow.com/q/11350978/1264909">stackoverflow</a> <a href="https://stackoverflow.com/questions/1870004/does-nsurlconnection-take-advantage-of-nsurlcache">questions</a> and <a href="http://nshipster.com/nsurlcache/" rel="nofollow noreferrer">searching</a> <a href="http://twobitlabs.com/2012/01/ios-ipad-iphone-nsurlcache-uiwebview-memory-utilization" rel="nofollow noreferrer">the</a> <a href="http://petersteinberger.com/blog/2012/nsurlcache-uses-a-disk-cache-as-of-ios5/" rel="nofollow noreferrer">web</a>, I decided to try the <strong>NSURLCache sharedURLCache</strong>, but I cannot figure out how it really works.</p> <p><strong>My testing scenario is this one:</strong></p> <p>I have implemented a test app for <strong>iOS 5</strong> where I have a single view with a UIWebView inside. This UiWebview is going to load a local <em>index.html</em> file like this:</p> <pre><code>// Create an NSString from the local HTML file NSString *fullURL = [[NSBundle mainBundle] pathForResource:@"index" ofType:@"html" inDirectory:@"www"]; NSURL *url = [NSURL fileURLWithPath:fullURL]; NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; // Load local HTML file [self.webView loadRequest:requestObj]; </code></pre> <p>In this <em>index.html</em> file, I have a JS script that downloads a JSON from Flickr with the last images uploaded to the their public feed. Each image is appended to a list. This whole process is repeated every second, until we reach 1000 images downloaded from the feed. See the code:</p> <pre><code>var nImg = 0; function getData() { $.getJSON('http://api.flickr.com/services/feeds/photos_public.gne?format=json&amp;jsoncallback=?', function(data) { var items = []; $.each(data.items, function(i, image) { items.push('&lt;li id="' + image.title + '"&gt;&lt;img src="' + image.media.m + '"/&gt;&lt;/li&gt;'); }); $('#page &gt; #imagesList').append(items.join'')); nImg += items.length; }); $('#page &gt; #numImages').html(nImg); if(nImg &lt; 1000) setTimeout("getData();", 1000); // Get more data in 1s } $(document).ready(function() { getData(); }); </code></pre> <p>Finally, in my AppDelegate, I set up the sharedURLCache as written in this <a href="http://nshipster.com/nsurlcache/" rel="nofollow noreferrer">post</a>:</p> <pre><code>// Initialize the Cache, so we can control the amount of memory it utilizes int cacheSizeMemory = 4*1024*1024; // 4MB int cacheSizeDisk = 32*1024*1024; // 32MB NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:cacheSizeMemory diskCapacity:cacheSizeDisk diskPath:nil]; [NSURLCache setSharedURLCache:sharedCache]; </code></pre> <p>But, despite what it is supposed to happen, when I open instruments and run the app checking the allocations, the memory keeps growing while we download images (up to 20MB), instead of flattening around 4-6MB as I would expect if the UIWebView would be using this sharedURLCache to cache the images downloaded.</p> <p><img src="https://i.stack.imgur.com/yn682.png" alt="Instruments evolution after we reach 1000 images"></p> <p>Does anybody know what am I doing wrong? Do I have misunderstood something? Am I loading the page wrong? Does the UIWebView uses another cache for the images loaded in the JS?</p> <p>Please, let me know your thoughts. I really need to understand how this sharedURLCache works, and how the UIWebView uses it to cache URLRequest, images,... in case it is used at all. <strong>I do not want to have an App that uses a UIWebView that can allocate memory without control.</strong></p>
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