为什么在 swiftui 中绑定到 Picker 不再起作用?

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 changeText("\(exercise)").tag(self.data.exercises.firstIndex(of: exercise))intoText("\(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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