导航栏透明代码 类似隐藏导航栏

//导航栏背景透明
[self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
//导航栏底部线清楚
self.navigationController.navigationBar.barStyle = UIBarStyleBlack;
self.navigationController.navigationBar.translucent = YES;
[self.navigationController.navigationBar setShadowImage:[UIImage new]];