列表中的第一项总是被选中 [英] First item in a List is always selected

问题描述

我有一个项目列表，我想让导航到详细信息视图成为可能.但是，列表中的第一个元素总是传递给这个视图，这可能是什么问题?

I have a list of items, I want to make it possible to navigate to the details view. However, the first element in the list is always passed to this view, what could be the problem?

struct ContentView: View {
    var array: [Object] = [Object(id: .init(),property: 1),Object(id: .init(),property: 2),Object(id: .init(),property: 3)]
    
    @State var showAlert = false
    @State var showDetailsView = false
    
    
    var body: some View {
        NavigationView{
            List{
                ForEach(array){ item in
                    VStack{
                        Text(String(item.property))
                    }.onTapGesture(){ self.showAlert.toggle()}
                    .alert(isPresented: $showAlert){
                        Alert(title: Text("show details view?"), message: Text(""),
                              primaryButton: .default (Text("Show")) {
                                showDetailsView.toggle()
                              },
                              secondaryButton: .cancel()
                        )
                    }
                    .fullScreenCover(isPresented: $showDetailsView){ DetailsView(property: item.property) }
                }
            }
        }
    }
}

struct Object: Identifiable {
    let id: UUID
    var property: Int
}

struct DetailsView: View {
    var property: Int?
    
    var body: some View {
        Text(String(property!))
    }
}

无论我选择列表中的哪个项目，我都会得到这个结果:

I will get this result regardless of which item in the list I select:

推荐答案

在这种情况下，我们可以将像指挥棒这样的点击项从 ForEach 传递到 Alert 到 FullScreen 到 Details.而且，当然，我们应该将相应的修饰符移出循环，它们不需要应用于每一行.

In this scenario we can pass clicked item like baton from ForEach to Alert to FullScreen to Details. And, of course, we should move corresponding modifiers out of cycle, they don't need to be applied to each row.

这是修改后的代码.使用 Xcode 12.1/iOS 14.1 测试.

Here is a modified code. Tested with Xcode 12.1 / iOS 14.1.

struct ContentView: View {
    var array: [Object] = [Object(id: .init(),property: 1),Object(id: .init(),property: 2),Object(id: .init(),property: 3)]
    
    @State var alertItem: Object?
    @State var selectedItem: Object?
    
    
    var body: some View {
        NavigationView{
            List{
                ForEach(array){ item in
                    VStack{
                        Text(String(item.property))
                    }.onTapGesture(){ self.alertItem = item}
                }
            }
              .alert(item: $alertItem) { item in
                    Alert(title: Text("show details view?"), message: Text(""),
                            primaryButton: .default (Text("Show")) {
                              selectedItem = item
                            },
                            secondaryButton: .cancel()
                    )
              }
              .fullScreenCover(item: $selectedItem){ DetailsView(property: $0.property) }
        }
    }
}

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