右滑返回与导航栏的显示隐藏优化

在viewWillAppear中加入以下代码，导航栏的显示隐藏动画与右滑返回的动画同步

- (void)viewWillAppear:(BOOL)animated{

    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:animated];
}