与AFNetworking在UICollectionView错误asynchronous下载

您好我正在创buildUICollection视图与清单目录，而点击单元格上的PDF必须下载，它在一个视图完美的工作，但在另一个视图给出的错误

* 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 

提前致谢。

Answer 1

当传递给此方法的CFURL为零时，CFURLCopyScheme崩溃，iOS7不检查传递给NSURLSessionDownloadTask的URL是否有效。

检查：

1）NSURL传递请求downloadTaskWithRequest不是零

2）NSURL不包含无效字符，例如：

 % |{}><"\`