导航条透明

设置导航条透明就是添加一张空图片，废话不多说直接上代码

- (void)viewDidLoad {    [super viewDidLoad];    /*     UIBarMetricsDefault,     UIBarMetricsCompact,     UIBarMetricsDefaultPrompt = 101, // Applicable only in bars with the prompt property, such as UINavigationBar and UISearchBar     UIBarMetricsCompactPrompt          */    [self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];    [self.navigationController.navigationBar setShadowImage:[UIImage new]];}

就是这么简单