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POImages wont load from iOS cache
 

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  1. POImages wont load from iOS cache
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    <p>So, I am attempting to save recently accessed images in the cache and load them back out if they are re-requested. The problem was the images requested from the cache did not show up but the images requested from the web did. However, after lots of fiddling I found that enclosing the cache data function up with a request on the main queue seemed to fix the issue. Can anyone explain to me why it works? I thought I would be on the main queue by default?</p> <pre><code>if([self.fileManager fileExistsAtPath:fileName]){ NSData *theData = [NSData dataWithContentsOfFile:fileName]; dispatch_async(dispatch_get_main_queue(), ^{ // Why does it work now? [self setUpScrollViewWithImageData:theData]; }); }else{ dispatch_queue_t downloadQueue = dispatch_queue_create("flickr download", NULL); dispatch_async(downloadQueue, ^{ NSData *imageData = [NSData dataWithContentsOfURL:image]; dispatch_async(dispatch_get_main_queue(), ^{ [self setUpScrollViewWithImageData:imageData]; [self.fileManager createFileAtPath:fileName contents:imageData attributes:nil]; [self checkCacheSize]; }); }); dispatch_release(downloadQueue); } </code></pre> <p>This is the scrollview setup method</p> <pre><code>-(void)setUpScrollViewWithImageData:(NSData *)imageDataToSetup{ UIImageView *myImage = [[UIImageView alloc] initWithImage:[UIImage imageWithData:imageDataToSetup]]; self.thisImage = myImage; self.myScrollView.delegate =self; self.myScrollView.contentSize = self.thisImage.bounds.size; self.navigationItem.rightBarButtonItem = nil; [self.myScrollView addSubview:self.thisImage]; self.myScrollView.minimumZoomScale = 0.2; self.myScrollView.maximumZoomScale = 5; float w = self.view.bounds.size.width/self.thisImage.bounds.size.width; float h = self.view.bounds.size.height/self.thisImage.bounds.size.height; float zoomRatioMax = MAX(w , h ); float zoomRatioMin = MIN(w , h ); if(zoomRatioMax&lt;1){ [self.myScrollView setZoomScale:zoomRatioMax]; } if(zoomRatioMin&gt;1){ [self.myScrollView setZoomScale:zoomRatioMin]; } } </code></pre>
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    1. PTQuestion
    1. USRob
    1. USChris Mitchelmore
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    1. COHi and welcome to StackOverflow. Please post your `setUpScrollViewWithImageData:` method.
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      1. POImages wont load from iOS cache
      1. USfzwo
    2. COThank you! Added it to the main body. Didn't think it was relevant :/
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      1. POImages wont load from iOS cache
      1. USChris Mitchelmore
    3. COUsually, UIKit methods must run on the main thread. I'm on the iPhone right now so can't try it, but try preparing the UIImage still in the background, without the main thread dispatch, and then do all UIKit stuff on the main thread.
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      1. POImages wont load from iOS cache
      1. USfzwo
 

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