SwiftUI

Question

我正在尝试实现一个用 "Slide from Botton" 动画呈现另一个场景的按钮。

PresentationButton 看起来不错，所以我试了一下：

import SwiftUI

struct ContentView : View {
    var body: some View {
        NavigationView {
            PresentationButton(destination: Green().frame(width: 1000.0)) {
                Text("Click")

                }.navigationBarTitle(Text("Navigation"))
        }
    }
}

#if DEBUG
struct ContentView_Previews : PreviewProvider {
    static var previews: some View {
        Group {
            ContentView()
                .previewDevice("iPhone X")
                .colorScheme(.dark)

            ContentView()
                .colorScheme(.dark)
                .previewDevice("iPad Pro (12.9-inch) (3rd generation)"

            )

        }

    }
}
#endif

结果如下：

我希望绿色视图覆盖整个屏幕，并且模态不是"draggable to close"。

是否可以为 PresentationButton 添加修饰符以使其全屏且不可拖动？

我也试过导航按钮，但是： - 它没有 "slide from bottom" - 它在详细视图上创建了一个 "back button"，我不想要

谢谢！

Answer 1

不幸的是，从 ~~Beta 2~~Beta 3 开始，这在纯 SwiftUI 中是不可能的。可以看到 Modal has no parameters for anything like UIModalPresentationStyle.fullScreen. Likewise for PresentationButton.

我建议提交雷达。

您目前可以做的最接近的事情是：

    @State var showModal: Bool = false
    var body: some View {
        NavigationView {
            Button(action: {
                self.showModal = true
            }) {
                Text("Tap me!")
            }
        }
        .navigationBarTitle(Text("Navigation!"))
        .overlay(self.showModal ? Color.green : nil)
    }

当然，您可以从那里在叠加层中添加您喜欢的任何过渡。

Answer 2

虽然我的其他答案目前是正确的，但人们现在可能希望能够这样做。我们可以使用 Environment 将视图控制器传递给 children。 Gist here

struct ViewControllerHolder {
    weak var value: UIViewController?
}


struct ViewControllerKey: EnvironmentKey {
    static var defaultValue: ViewControllerHolder { return ViewControllerHolder(value: UIApplication.shared.windows.first?.rootViewController ) }
}

extension EnvironmentValues {
    var viewController: UIViewControllerHolder {
        get { return self[ViewControllerKey.self] }
        set { self[ViewControllerKey.self] = newValue }
    }
}

向 UIViewController 添加扩展

extension UIViewController {
    func present<Content: View>(style: UIModalPresentationStyle = .automatic, @ViewBuilder builder: () -> Content) {
        // Must instantiate HostingController with some sort of view...
        let toPresent = UIHostingController(rootView: AnyView(EmptyView()))
        toPresent.modalPresentationStyle = style
        // ... but then we can reset rootView to include the environment
        toPresent.rootView = AnyView(
            builder()
                .environment(\.viewController, ViewControllerHolder(value: toPresent))
        )
        self.present(toPresent, animated: true, completion: nil)
    }
}

只要我们需要，就使用它：

struct MyView: View {

    @Environment(\.viewController) private var viewControllerHolder: ViewControllerHolder
    private var viewController: UIViewController? {
        self.viewControllerHolder.value
    }

    var body: some View {
        Button(action: {
           self.viewController?.present(style: .fullScreen) {
              MyView()
           }
        }) {
           Text("Present me!")
        }
    }
}

[EDIT] 虽然最好做类似 @Environment(\.viewController) var viewController: UIViewController? 的事情，但这会导致保留周期。因此，您需要使用支架。

Answer 3

所以我为此苦苦挣扎，我不喜欢覆盖功能和 ViewController 包装版本，因为它给我带来了一些内存错误，我对 iOS 很陌生，只知道SwiftUI，没有 UIKit。

我仅使用 SwiftUI 开发了以下内容，这可能是叠加层所做的，但就我的目的而言，它更加灵活：

struct FullscreenModalView<Presenting, Content>: View where Presenting: View, Content: View {

    @Binding var isShowing: Bool
    let parent: () -> Presenting
    let content: () -> Content

    @inlinable public init(isShowing: Binding<Bool>, parent: @escaping () -> Presenting, @ViewBuilder content: @escaping () -> Content) {
        self._isShowing = isShowing
        self.parent = parent
        self.content = content
    }

    var body: some View {
        GeometryReader { geometry in
            ZStack {
                self.parent().zIndex(0)
                if self.$isShowing.wrappedValue {
                    self.content()
                    .background(Color.primary.colorInvert())
                    .edgesIgnoringSafeArea(.all)
                    .frame(width: geometry.size.width, height: geometry.size.height)
                    .transition(.move(edge: .bottom))
                    .zIndex(1)

                }
            }
        }
    }
}

正在为 View 添加扩展：

extension View {

    func modal<Content>(isShowing: Binding<Bool>, @ViewBuilder content: @escaping () -> Content) -> some View where Content: View {
        FullscreenModalView(isShowing: isShowing, parent: { self }, content: content)
    }

}

用法：使用自定义视图并将 showModal 变量作为 Binding<Bool> 传递，以从视图本身中消除模式。

struct ContentView : View {
    @State private var showModal: Bool = false
    var body: some View {
        ZStack {
            Button(action: {
                withAnimation {
                    self.showModal.toggle()
                }
            }, label: {
                HStack{
                   Image(systemName: "eye.fill")
                    Text("Calibrate")
                }
               .frame(width: 220, height: 120)
            })
        }
        .modal(isShowing: self.$showModal, content: {
            Text("Hallo")
        })
    }
}

希望对您有所帮助！

你好 krjw

Answer 4

此版本修复了 XCode 11.1 中存在的编译错误，并确保控制器以传入的样式呈现。

import SwiftUI

struct ViewControllerHolder {
    weak var value: UIViewController?
}

struct ViewControllerKey: EnvironmentKey {
    static var defaultValue: ViewControllerHolder {
        return ViewControllerHolder(value: UIApplication.shared.windows.first?.rootViewController)

    }
}

extension EnvironmentValues {
    var viewController: UIViewController? {
        get { return self[ViewControllerKey.self].value }
        set { self[ViewControllerKey.self].value = newValue }
    }
}

extension UIViewController {
    func present<Content: View>(style: UIModalPresentationStyle = .automatic, @ViewBuilder builder: () -> Content) {
        let toPresent = UIHostingController(rootView: AnyView(EmptyView()))
        toPresent.modalPresentationStyle = style
        toPresent.rootView = AnyView(
            builder()
                .environment(\.viewController, toPresent)
        )
        self.present(toPresent, animated: true, completion: nil)
    }
}

使用此版本，代码与上一版本无变化

struct MyView: View {

    @Environment(\.viewController) private var viewControllerHolder: UIViewController?
    private var viewController: UIViewController? {
        self.viewControllerHolder.value
    }

    var body: some View {
        Button(action: {
           self.viewController?.present(style: .fullScreen) {
              MyView()
           }
        }) {
           Text("Present me!")
        }
    }
}

Answer 5

我对此的解决方案（您可以轻松扩展以允许调整所呈现的 sheet 上的其他参数）是仅子class UIHostingController

//HSHostingController.swift

import Foundation
import SwiftUI

class HSHostingControllerParams {
    static var nextModalPresentationStyle:UIModalPresentationStyle?
}

class HSHostingController<Content> : UIHostingController<Content> where Content : View {

    override func present(_ viewControllerToPresent: UIViewController, animated flag: Bool, completion: (() -> Void)? = nil) {

        if let nextStyle = HSHostingControllerParams.nextModalPresentationStyle {
            viewControllerToPresent.modalPresentationStyle = nextStyle
            HSHostingControllerParams.nextModalPresentationStyle = nil
        }

        super.present(viewControllerToPresent, animated: flag, completion: completion)
    }

}

在场景委托中使用 HSHostingController 而不是 UIHostingController 像这样：

    // Use a HSHostingController as window root view controller.
    if let windowScene = scene as? UIWindowScene {
        let window = UIWindow(windowScene: windowScene)

        //This is the only change from the standard boilerplate
        window.rootViewController = HSHostingController(rootView: contentView)

        self.window = window
        window.makeKeyAndVisible()
    }

然后在触发 sheet

之前告诉 HSHostingControllerParams class 你想要什么样的展示风格

        .navigationBarItems(trailing:
            HStack {
                Button("About") {
                    HSHostingControllerParams.nextModalPresentationStyle = .fullScreen
                    self.showMenuSheet.toggle()
                }
            }
        )

通过 class 单例传递参数感觉有点 'dirty'，但在实践中 - 您必须创建一个非常模糊的场景才能使其无法按预期工作。

您可能会弄乱环境变量等（正如其他答案所做的那样）-但对我来说，增加的复杂性不值得纯粹。

更新：请参阅 this gist 以了解具有附加功能的扩展解决方案

Answer 6

Xcode 12.0 - SwiftUI 2 - iOS 14

现在可以了。使用 fullScreenCover() 修饰符。

var body: some View {
    Button("Present!") {
        self.isPresented.toggle()
    }
    .fullScreenCover(isPresented: $isPresented, content: FullScreenModalView.init)
}

Hacking With Swift

SwiftUI - 带有全屏模式的 PresentationButton

SwiftUI - PresentationButton with modal that is full screen

xcode11