如何在SplitViewController上放置相同的背景？

import UIKit

class CustomViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置背景图片
        let backgroundImage = UIImage(named: "background.jpg")
        let backgroundImageView = UIImageView(image: backgroundImage)
        backgroundImageView.frame = view.bounds
        backgroundImageView.contentMode = .scaleAspectFill
        view.addSubview(backgroundImageView)
        
        // 或者设置背景颜色
        view.backgroundColor = UIColor.blue
    }
}

// 在AppDelegate中设置SplitViewController的主视图控制器为自定义视图控制器
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    let splitViewController = UISplitViewController()
    let customViewController = CustomViewController()
    splitViewController.viewControllers = [customViewController]
    
    // 其他配置...
    
    window?.rootViewController = splitViewController
    window?.makeKeyAndVisible()
    
    return true
}