为什么在 swiftui 中绑定到 Picker 不再起作用? [英] Why does binding to the Picker not work anymore in swiftui?

问题描述

当我在模拟器或画布中运行选择器代码时，选择器总是返回第一个选项并带有动画或只是冻结.这发生在上周四/周五.所以我检查了一些旧的简单代码，在那之前它可以工作，但对我来说也不起作用.这是简单的旧代码.它不再适用于 beta 3、4 和 5.

When I run a Picker Code in the Simulator or the Canvas, the Picker goes always back to the first option with an animation or just freezes. This happens since last Thursday/Friday. So I checked some old simple code, where it worked before that and it doesn't work for me there, too. This is the simple old Code. It doesn't work anymore in beta 3, 4 and 5.

struct PickerView : View {
    @State var selectedOptionIndex = 0

    var body: some View {
        VStack {
            Text("Option: \(selectedOptionIndex)")
            Picker(selection: $selectedOptionIndex, label: Text("")) {
                Text("Option 1")
                Text("Option 2")
                Text("Option 3")
            }
        }
    }
}

在我较新的代码中，我使用了 @ObservedObject，但在这里它也不起作用.此外，我没有收到任何错误，并且它可以构建和运行.感谢您的指点.

In my newer code, I used @ObservedObject, but also here it doesn't work. Also I don't get any errors and it builds and runs. Thank you for any pointers.

----EDIT----- 请先看答案

在帮助之后，我可以在所有 Text() 后面使用 .tag()，例如 Text("Option 1").tag()，它现在采用初始值并在视图中更新它.如果我像这里一样使用 @ObservedObject:

After the help, that I could use the .tag() behind all Text()like Text("Option 1").tag(), it now takes the initial value and updates it inside the view. If I use @ObservedObject like here:

struct PickerView: View {
    @ObservedObject var data: Model

    let width: CGFloat
    let height: CGFloat

    var body: some View {
        VStack(alignment: .leading) {
            Picker(selection: $data.exercise, label: Text("select exercise")) {
                    ForEach(data.exercises, id: \.self) { exercise in
                        Text("\(exercise)").tag(self.data.exercises.firstIndex(of: exercise))
                    }
                }
.frame(width: width, height: (height/2), alignment: .center)
            }
       }
    }
}  

不幸的是，它没有反映值的变化，如果我在另一个视图中进行这些更改，一个导航链接.而且它似乎不适用于我上面的代码，我在其中使用 firstIndex(of: Exercise)

Unfortunately it doesn't reflect changes on the value, if I make these changes in another view, one navigationlink further. And also it doesn't seem to work with the my code above, where I use firstIndex(of: exercise)

---编辑---现在如果我改变上面的代码Text("\(exercise)").tag(self.data.exercises.firstIndex(of:exercise))进入Text("\(exercise)").tag(self.data.exercises.firstIndex(of:exercise)!)因为它不能与可选的一起使用.

---EDIT--- Now the code above works if I change Text("\(exercise)").tag(self.data.exercises.firstIndex(of: exercise)) into Text("\(exercise)").tag(self.data.exercises.firstIndex(of: exercise)!) because it couldn't work with an optional.

推荐答案

答案总结:

1. 使用 .tag() 后面的选项它可以工作.它看起来像下面这样:

1. With the .tag() behind the Options it works. It would look like following:

Picker(selection: $selectedOptionIndex, label: Text("")) {
                ForEach(1...3) { index in
                    Text("Option \(index)").tag(index)
                }
            }

1. 如果您使用一系列对象，它可能如下所示:

Picker(selection: $data.exercises, label: Text("")) {
                ForEach(0..<data.exercises.count) { index in
                    Text("\(data.exercises[index])").tag(index)
                }
            }

我不确定它是否有意，此处需要使用 .tag() ，但这至少是一种解决方法.

I am not sure if it is intended, that .tag() is needed to be used here, but it's at least a workaround.

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