Question

因此，我想使用SwiftUI呈现一个新视图，而无需用户点击按钮，因为NavigationButton可以使用它。这是一个例子

struct ContentView : View {

    var model: Model

    var body: some View {
        NavigationView {
            Text("Hello World")
        }.onAppear {
            if model.shouldPresent {
                // present a new view
            }
        }
    }
}

在onAppear中，我想包含一些将新视图推送到导航堆栈上的代码。

Answer 1

这是一种将视图显示为模态的方法。

Scenario: ...
    Given I drop the file to the server's UNC path
    When the file is processed successfully
    Then a new account is loaded

类似地，如果您希望控制是否使用变量来显示，则可以执行以下操作。

struct PresentOnloadView: View {
    var body: some View {
        HStack {
            Text("Hey there")
            }
            .presentation(Modal(HelloView(), onDismiss: nil))
        }
}

struct HelloView: View {
    var body: some View {
        Text("Whats up! ?")
    }
}

Answer 2

在您的视图内：

@State var present = true

var body: some View {
    NavigationLink(destination: DestinationView(), isActive: $present) {
        EmptyView()
    }
}

导航链接加载后，此代码立即显示DestinationView。关键部分是isActive参数，该参数以编程方式触发向其他视图的过渡。

您可以重写如下

@State var present = false

var body: some View {
    NavigationLink(destination: DestinationView(), isActive: $present) {
        Button { 
            present = true
        } label: { Text("Present") }
    }
}

要手动创建导航按钮。

Answer 3

您只需将逻辑放在NavigationView中。像这样：

@State var x = true;

var body : some View {
    NavigationView {
        if x {
            Text("Hello")
            Button(action: {
                self.x = false;
            }, label: { Text("Click Me") })
        } else {
            Text("World")
        }
    }
}

Answer 4

SwiftUI 2

SwiftUI 2 / iOS 14 中的 Segue 等效项：

显示（推送）

struct ContentView: View {
    @State var showSecondView = false

    var body: some View {
        NavigationView {
            Text("First view")
                .background(NavigationLink("", destination: Text("Second view"), isActive: $showSecondView))
        }
        .onAppear {
            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
                showSecondView = true
            }
        }
    }
}

显示详细信息（替换）

struct ContentView: View {
    @State private var showSecondView = false

    var body: some View {
        NavigationView {
            if showSecondView {
                Text("Second view")
            } else {
                Text("First view")
            }
        }
        .onAppear {
            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
                showSecondView = true
            }
        }
    }
}

模态呈现

struct ContentView: View {
    @State private var showSecondView = false

    var body: some View {
        NavigationView {
            Text("First view")
        }
        .sheet(isPresented: $showSecondView) {
            Text("Second view")
        }
        .onAppear {
            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
                showSecondView = true
            }
        }
    }
}

全屏显示

struct ContentView: View {
    @State private var showSecondView = false

    var body: some View {
        NavigationView {
            Text("First view")
        }
        .fullScreenCover(isPresented: $showSecondView) {
            Text("Second view")
        }
        .onAppear {
            DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
                showSecondView = true
            }
        }
    }
}

注意：我添加了 DispatchQueue.main.asyncAfter(deadline: .now() + 1) 以便您可以看到过渡。您可以删除它，过渡将立即开始。

无需按钮即可在SwiftUI中呈现新视图

4 个答案:

SwiftUI 2