1.菜單詳情界面：
①xib 中設置為formSheet
②
MainViewController *mainVC = [[MainViewController alloc]init];
mainVC.modalPresentationStyle = UIModalPresentationFormSheet;
mainVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentViewController:mainVC animated:YES completion:nil];
2.關(guān)掉自動布局：
重點：選iPad
然后詳情彈出窗體背景圖片才能正常顯示
