if(@available(iOS13,*)) {
? ? ? ? UINavigationBarAppearance *appearance = [[UINavigationBarAppearance alloc]init];
? ? ? ? appearance.backgroundColor = [UIColor whiteColor];
? ? ? ? appearance.shadowColor = [UIColor clearColor];
? ? ? ? [UINavigationBar appearance].standardAppearance = appearance;
? ? ? ? [UINavigationBar appearance].scrollEdgeAppearance = appearance;
? ? }
