iOS导航栏颜色

-(void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    //通过设置BackgroundImage来设置导航的背景
    //设置背景为透明
    [self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setShadowImage:[UIImage new]];
}

-(void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    
    //还原为系统默认
    [self.navigationController.navigationBar setBackgroundImage:nil forBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setShadowImage:nil];
}