swiftUI tabView如何设置默认视图onAppear？

Question

我有一个带有多个视图的 tabView，我想知道如何在加载时取消定义默认视图。 默认情况下，Xcode 分配第一个视图，但我希望在启动应用程序时加载第二个视图。

var body: some Scene {
    WindowGroup {
        TabView {
            alertView()
            todayView()
            forecastView()
        }
        .tabViewStyle(PageTabViewStyle(indexDisplayMode: .always))
        .onAppear
        {
            UIPageControl.appearance().currentPageIndicatorTintColor = .black
            UIPageControl.appearance().pageIndicatorTintColor = UIColor.black.withAlphaComponent(0.2)
        }
    }
}

Answer 1

让我们在显式场景根视图中移动所有内容

var body: some Scene {
    WindowGroup {
      ContentView()
    }
}

现在我们可以为此使用selection ，例如

struct ContentView: View {
  @State private var selection = 2   // << here !!

  var body: some View {
        TabView(selection: $selection) {   // << here !!
            alertView().tag(1)        
            todayView().tag(2)             // << here !!
            forecastView().tag(3)
        }
        .tabViewStyle(PageTabViewStyle(indexDisplayMode: .always))
        .onAppear
        {
            UIPageControl.appearance().currentPageIndicatorTintColor = .black
            UIPageControl.appearance().pageIndicatorTintColor = UIColor.black.withAlphaComponent(0.2)
        }
  }
}