iOS 在启动时显示模态视图控制器而不使用 Flash

在iOS应用程序中，启动时显示模态视图控制器是一种常见的需求。模态视图控制器可以在应用程序启动后立即呈现给用户，提供一种引导用户进行某些操作或提供重要信息的方式。与使用Flash进行启动屏幕动画相比，使用模态视图控制器可以更加简洁和高效。

swift
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // 创建启动界面视图控制器
    let splashViewController = SplashViewController()
    
    // 设置启动界面视图控制器的样式和展示方式
    splashViewController.modalPresentationStyle = .overFullScreen
    splashViewController.modalTransitionStyle = .crossDissolve
    
    // 获取根视图控制器
    guard let rootViewController = window?.rootViewController else {
        return true
    }
    
    // 呈现启动界面视图控制器
    rootViewController.present(splashViewController, animated: false, completion: nil)
    
    return true
}

swift
class SplashViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置背景颜色
        view.backgroundColor = .white
        
        // 创建应用程序标志
        let logoImageView = UIImageView(image: UIImage(named: "app_logo"))
        logoImageView.contentMode = .scaleAspectFit
        logoImageView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(logoImageView)
        
        // 创建应用程序名称标签
        let nameLabel = UILabel()
        nameLabel.text = "MyApp"
        nameLabel.font = UIFont.systemFont(ofSize: 24, weight: .bold)
        nameLabel.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(nameLabel)
        
        // 添加约束
        NSLayoutConstraint.activate([
            logoImageView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            logoImageView.centerYAnchor.constraint(equalTo: view.centerYAnchor, constant: -50),
            logoImageView.widthAnchor.constraint(equalToConstant: 100),
            logoImageView.heightAnchor.constraint(equalToConstant: 100),
            
            nameLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            nameLabel.topAnchor.constraint(equalTo: logoImageView.bottomAnchor, constant: 20)
        ])
    }
}