IOS 去掉导航栏（UINavigationBar）下方的横线

这是导航栏的问题，将下边的代码放在  viewWillAppear  方法中就可以实现效果：

- (void)viewWillAppear:(BOOL)animated{

// Called when the view is about to made visible. Default does nothing

[super viewWillAppear:animated];

//去除导航栏下方的横线

[navigationBar setBackgroundImage:[UIImage imageWithColor:[self colorFromHexRGB:@"33cccc"]]

forBarPosition:UIBarPositionAny

barMetrics:UIBarMetricsDefault];

[navigationBar setShadowImage:[UIImage new]];

}