控制器隐藏了导航 下页pop 导航位置看到黑条

解决：

-(void)viewWillDisappear:(BOOL)animated{
    
    [super viewWillDisappear:animated];
    [self.navigationController setNavigationBarHidden:NO animated:NO];
    
}

-(void)viewWillAppear:(BOOL)animated{
    
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:YES];
    
}