代码如下：
let bgImageView = UIImageView(image: UIImage(named: "tabbar_bgImage"))
bgImageView.frame = mainTabBarVc.tabBar.bounds
bgImageView.contentMode = .scaleAspectFill
// 移除原有背景并添加新背景
if let subviews = mainTabBarVc.tabBar.subviews as? UIView {
for subview in subviews {
// 识别背景视图（包含"Background"关键字的类名）
if String(describing: type(of: subview)).contains("Background") {
subview.removeFromSuperview()
break
}
}
}
mainTabBarVc.tabBar.insertSubview(bgImageView, at: 0)