最初，modalPresentationStyle的默认值是全屏，但在iOS 13中，它的变化是UIModalPresentationStyle.automatic。

如果你想要创建全屏视图控制器，你必须将modalPresentationStyle更改为fullScreen。

参考UIModalPresentationStyle苹果文档了解更多细节，并参考苹果人机界面指南了解应该在哪里使用哪种模式。

我添加的信息可能对某人有用。如果你有任何故事板segue，要回到旧的风格，你需要将kind属性设置为modal Present，并将Presentation属性设置为全屏。

let Obj = MtViewController()
Obj.modalPresentationStyle = .overFullScreen
self.present(Obj, animated: true, completion: nil)

//如果你想禁用滑动来消除它，添加行

Obj.isModalInPresentation = true

查看苹果文档获取更多信息。

class MyViewController: UIViewController {

    convenience init() {
        self.init(nibName:nil, bundle:nil)
        self.modalPresentationStyle = .fullScreen
    }

    override func viewDidLoad() {
        super.viewDidLoad()
    }
}

而不是调用self。modalPresentationStyle = . fullscreen对于每个视图控制器，你可以子类化UIViewController并在任何地方使用MyViewController。

设置导航控制器。modalPresentationStyle到。fullscreen已经重复了一千多次了，但让我给你们展示另一个阻止器，它会导致UIViewController / UINavigationController没有在全屏显示，即使所有的属性都设置正确。

对我来说，罪魁祸首就藏在这条线里

navigationController?.presentationController?.delegate = self

显然，当设置UIAdaptivePresentationControllerDelegate时，你需要在可选的delegate方法中指定表示样式

    public func adaptivePresentationStyle(for controller: UIPresentationController) -> UIModalPresentationStyle {
        presentationStyle
    }

我通过使用方法swizzling(Swift 4.2)实现了它:

创建UIViewController扩展，如下所示

extension UIViewController {

    @objc private func swizzled_presentstyle(_ viewControllerToPresent: UIViewController, animated: Bool, completion: (() -> Void)?) {

        if #available(iOS 13.0, *) {
            if viewControllerToPresent.modalPresentationStyle == .automatic || viewControllerToPresent.modalPresentationStyle == .pageSheet {
                viewControllerToPresent.modalPresentationStyle = .fullScreen
            }
        }

        self.swizzled_presentstyle(viewControllerToPresent, animated: animated, completion: completion)
    }

     static func setPresentationStyle_fullScreen() {

        let instance: UIViewController = UIViewController()
        let aClass: AnyClass! = object_getClass(instance)

        let originalSelector = #selector(UIViewController.present(_:animated:completion:))
        let swizzledSelector = #selector(UIViewController.swizzled_presentstyle(_:animated:completion:))

        let originalMethod = class_getInstanceMethod(aClass, originalSelector)
        let swizzledMethod = class_getInstanceMethod(aClass, swizzledSelector)
        if let originalMethod = originalMethod, let swizzledMethod = swizzledMethod {
        method_exchangeImplementations(originalMethod, swizzledMethod)
        }
    }
}

在AppDelegate中，在application:didFinishLaunchingWithOptions中:调用swizzling代码通过调用:

UIViewController.setPresentationStyle_fullScreen()