让导航栏透明的办法

设置一张透明的背景图片让导航栏透明

//设置背景图
[self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"blank"] forBarMetrics:UIBarMetricsDefault];
//通过设置shadowImage移除黑线
[self.navigationController.navigationBar.shadowImage = [UIImage new];
//设置标题字体大小与颜色
[self.navigationController.navigationBar setTitleTextAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:19],NSForegroundColorAttributeName:[UIColor whiteColor]}];
//设置返回按钮字体颜色
[self.navigationController.navigationBar setTintColor:[UIColor whiteColor]];