点击共享button时，QLPreviewController崩溃，内部一致性笔尖包错误

我正在呈现一个QLPreviewController模态。 一切正常 – popup，显示预览项目和一切。 但是，一旦分享button被轻敲，应用程序崩溃在设备上，并在模拟器中：

2013-05-03 20:10:53.563 appname[16860:c07] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Could not load NIB in bundle: 'NSBundle <{{app_path}}> (loaded)' with name '_UIDocumentActivityViewController'' 

这是相关的代码：

 #pragma mark HVSchedulesDelegate - (void)schedulePDFReceived { QLPreviewController *previewController = [[QLPreviewController alloc] init]; [previewController setDataSource:self]; [self presentViewController:previewController animated:YES completion:nil]; } #pragma mark QLPreviewControllerDataSource - (NSInteger) numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller { return 1; } - (id <QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index { return [NSURL fileURLWithPath:self.schedulesProxy.pdfPath]; }