Ios 没有用于在UISplitViewController中显示和隐藏主UIViewController的动画，用于后续演示（primaryEdge=.training）

因此，我在AppDelegate中使用了具有以下配置的UISplitViewController：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    window = UIWindow(frame: UIScreen.main.bounds)
    let splitVC = UISplitViewController()
    let masterVC = UIViewController()
    let detailVC = UIViewController()
    splitVC.viewControllers = [masterVC, detailVC]
    splitVC.preferredDisplayMode = .primaryHidden
    splitVC.primaryEdge = .trailing
    window!.backgroundColor = .white
    window!.rootViewController = splitVC
    window!.makeKeyAndVisible()
    return true
}

由于我使用的主VCs和详细VCs没有导航控制器，因此我在UISplitViewController扩展中编写了一些用于切换（显示/隐藏）主VCs的函数：

extension UISplitViewController {
func showMasterView(from edge: PrimaryEdge = .leading,  completion: (()->Void)? = nil) {
    primaryEdge = edge
    UIView.animate(withDuration: 0.5, animations: {
        self.preferredDisplayMode = .allVisible
    }) { (animationFinished) in
        if let completion = completion, animationFinished {
            completion()
        }
    }
}

func hideMasterView(completion: (()->Void)? = nil) {
    UIView.animate(withDuration: 0.5, animations: {
        self.preferredDisplayMode = .primaryHidden
    }) { (animationFinished) in
        if let completion = completion, animationFinished {
            completion()
        }
    }
}


func toggleMasterView( completion: (()->Void)? = nil) {
    var nextDisplayMode: UISplitViewController.DisplayMode
    switch(self.preferredDisplayMode) {
    case .primaryHidden:
        nextDisplayMode = .allVisible
    default:
        nextDisplayMode = .primaryHidden
    }
    UIView.animate(withDuration: 0.5, animations: {
        self.preferredDisplayMode = nextDisplayMode
    }) { (animationFinished) in
        if let completion = completion, animationFinished {
            completion()
        }
    }
}

func toggleMasterViewNew() {
   let barButtonItem = self.displayModeButtonItem
   UIApplication.shared.sendAction(barButtonItem.action!, to: barButtonItem.target, from: nil, for: nil)
}
}

当splitVC.primaryEdge=.leading（默认情况下）时，这些函数对动画非常有用，但不适用于.Training-动画出现故障时，主vc仅用于显示和隐藏。 我知道我可以编写自定义解决方案，但我想知道，为什么。拖尾演示破坏了切换动画

所以，我希望我们能一起找到答案：）