iOS : getting crash while choosing that see pageviewcontroller for first time that apps loaded

Question

嗨，我按照堆栈中的一些教程只看到 UIPageviewcontroller 第一次运行我找到了最好的一个，而不是在应用程序委托(delegate)中实现它....首先我只有一个 Storyboard两个 viewcontroller 其中第一个是我的 PageViewController 第二个是我的 Loginvc我在 appdelegate 上实现了这段代码，但我崩溃了，一切看起来都不错，但我崩溃了，这是我实现的代码

var window: UIWindow?
var story : UIStoryboard?


func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    UIApplication.shared.statusBarStyle = .lightContent

    window = UIWindow(frame: UIScreen.main.bounds)
    window?.makeKeyAndVisible()

    let lunchedBefore = UserDefaults.standard.bool(forKey: "lunchedBefore")

    if lunchedBefore {
        story = UIStoryboard(name: "TShopUI", bundle: nil)
        let rootcontroller = story?.instantiateViewController(withIdentifier: "LoginVC")
        if let window = self.window {
            window.rootViewController = rootcontroller
        }
    } else {

        UserDefaults.standard.set(true, forKey: "lunchedBefore")
        story = UIStoryboard(name: "TShopUI", bundle: nil)
        let rootcontroller = story?.instantiateViewController(withIdentifier: "MainVC")

        if let window = self.window {
            window.rootViewController = rootcontroller
        }

    }
    return true
}

谢谢你的帮助请尽可能清楚地回答我是 iOS 开发的新手

Answer 1

它因为 UserDefaults 而崩溃，你必须像下面那样处理 UserDefaults，

更新:我们可以使用object 代替Bool。所以无论if条件是否满足，都不是第一次启动。 else 首次启动。

var window: UIWindow?
var story : UIStoryboard?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    UIApplication.shared.statusBarStyle = .lightContent
    window = UIWindow(frame: UIScreen.main.bounds)
    window?.makeKeyAndVisible()
    if let lunchedBefore = UserDefaults.standard.object(forKey: "lunchedBefore") {
        story = UIStoryboard(name: "TShopUI", bundle: nil)
        let rootcontroller = story?.instantiateViewController(withIdentifier: "LoginVC")
        if let window = self.window {
            window.rootViewController = rootcontroller
        }
    } else {
        UserDefaults.standard.set(true, forKey: "lunchedBefore")
        story = UIStoryboard(name: "TShopUI", bundle: nil)
        let rootcontroller = story?.instantiateViewController(withIdentifier: "MainVC")
        if let window = self.window {
            window.rootViewController = rootcontroller
        }
    }
    return true
}