Hi I'm creating Uicollection view with list ofcatalogs, While tapping on cell the PDF have to download, Its working in one view perfectly but in another view gives the error
* thread #1: tid = 0x4b2ce, 0x000000018d14f9b8 CoreFoundation`CFURLCopyScheme + 56, queue = 'com.apple.NSURLSession-work', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
frame #0: 0x000000018d14f9b8 CoreFoundation`CFURLCopyScheme + 56
frame #1: 0x000000018cdab96c CFNetwork`_urlIsHTTPish + 16
frame #2: 0x000000018cdc76b0 CFNetwork`URLRequest::addOverridingSessionAttributes(_CFURLSessionConfiguration*) + 288
frame #3: 0x000000018ce38964 CFNetwork`ClassicConnectionSession::createConnectionWithProperties(_CFURLRequest const*, __CFDictionary const*) const + 548
frame #4: 0x000000018ce10bcc CFNetwork`__73-[__NSCFLocalSessionBridge downloadTaskForRequest:resumeData:completion:]_block_invoke + 224
frame #5: 0x000000019a0abfd4 libdispatch.dylib`_dispatch_client_callout + 16
frame #6: 0x000000019a0b1c84 libdispatch.dylib`_dispatch_barrier_sync_f_invoke + 48
frame #7: 0x000000018cd977f4 CFNetwork`-[__NSCFLocalSessionTask resume] + 108
* frame #8: 0x00000001001b34d0 HSPCatalogApp`-[MRItem AsynchronousDownload12:] (self=0x0000000170297110, _cmd=0x00000001005a3109, UrlString=0x00000001700fd800) + 548 at MRItem.m:154
frame #9: 0x00000001001b3084 HSPCatalogApp`-[MRItem downloadItem](self=0x0000000170297110, _cmd=0x0000000100599f1f) + 652 at MRItem.m:56
frame #10: 0x00000001000f7c6c HSPCatalogApp`-[HWFilterViewController collectionView:didSelectItemAtIndexPath:](self=0x0000000125568ae0, _cmd=0x00000001908d74db, collectionView=0x00000001258c2a00, indexPath=0xc000000000008016) + 960 at HWFilterViewController.m:484
frame #11: 0x0000000190428d44 UIKit`-[UICollectionView touchesEnded:withEvent:] + 448
frame #12: 0x00000001903875e0 UIKit`forwardTouchMethod + 268
frame #13: 0x00000001903875e0 UIKit`forwardTouchMethod + 268
frame #14: 0x00000001901d5df4 UIKit`_UIGestureRecognizerUpdate + 5032
frame #15: 0x0000000190213b08 UIKit`-[UIWindow _sendGesturesForEvent:] + 1012
frame #16: 0x0000000190213218 UIKit`-[UIWindow sendEvent:] + 828
frame #17: 0x00000001901e4b50 UIKit`-[UIApplication sendEvent:] + 256
frame #18: 0x00000001901e2c40 UIKit`_UIApplicationHandleEventQueue + 8500
frame #19: 0x000000018d1db7f4 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
frame #20: 0x000000018d1dab50 CoreFoundation`__CFRunLoopDoSources0 + 256
frame #21: 0x000000018d1d8de8 CoreFoundation`__CFRunLoopRun + 632
frame #22: 0x000000018d119dd0 CoreFoundation`CFRunLoopRunSpecific + 452
frame #23: 0x0000000192da9c0c GraphicsServices`GSEventRunModal + 168
frame #24: 0x000000019024afc4 UIKit`UIApplicationMain + 1156
frame #25: 0x000000010013e64c HSPCatalogApp`main(argc=1, argv=0x000000016fd17c98) + 116 at main.m:16
frame #26: 0x000000019a0c7aa0 libdyld.dylib`start + 4
thanks in advance.
CFURLCopyScheme crashed as CFURL passed to this method is nil, iOS7 does not check if url passed to NSURLSessionDownloadTask is valid.
Check that:
1) NSURL passed to request downloadTaskWithRequest was not nil
2) NSURL does not contain invalid characters e.g:
% |{}><"\`
来源：https://stackoverflow.com/questions/25266727/asynchronous-downloading-in-uicollectionview-error-with-afnetworking