导航栏的隐藏与切换解决方案

导航栏隐藏之后切换到下一页面之后，可能会有一下问题，转场很生硬。

(参考链接)[https://www.jianshu.com/p/7bec9ea95c86]

-(void)viewWillAppear:(BOOL)animated{
    if (self.tabBarController.selectedIndex == 当前tab下标) {
        [self.navigationController setNavigationBarHidden:YES animated:YES];
    } else {
        [self.navigationController setNavigationBarHidden:YES animated:NO];
    }
}
-(void)viewWillDisappear:(BOOL)animated{
    [self.navigationController setNavigationBarHidden:NO animated:YES];
}