1、背景色变黑

# oc
if ([@available](https://github.com/available)(iOS 15.0, *)) {
    UITabBarAppearance *appearance = [UITabBarAppearance new];
    [appearance configureWithOpaqueBackground];
    appearance.backgroundColor = [UIColor white];
    self.tabBar.standardAppearance = appearance;
    self.tabBar.scrollEdgeAppearance = appearance;
} else {
    [[UITabBar appearance] setBarTintColor:[UIColor white]];
}

#swift
if #available(iOS 15.0, *) {
    let appearance = UITabBarAppearance()
    appearance.backgroundColor = UIColor.white
    self.tabBar.standardAppearance = appearance
    self.tabBar.scrollEdgeAppearance = appearance
}