1.菜单详情界面：
①xib 中设置为formSheet
②
MainViewController *mainVC = [[MainViewController alloc]init];
mainVC.modalPresentationStyle = UIModalPresentationFormSheet;
mainVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentViewController:mainVC animated:YES completion:nil];
2.关掉自动布局：
重点：选iPad
然后详情弹出窗体背景图片才能正常显示
