选择器（SegmentedPickerStyle）中的选择效果不佳 - SwiftUI

Question

我有风格选择器SegmentedPickerStyle()。现在我正在根据选择器值进行一些计算，并且它正在工作。但不知何故，如果我点击它，我的选择器不会改变它的选择值。要更改选择值，我需要滑动这些值。
另一个问题是，如果我需要计算TipAmount，那么首先我需要滑动到选择器值，然后需要选择该值。我不知道为什么会这样！！

这是我的查看代码，

struct ContentView: View {

    @ObservedObject var tipViewModel = TipViewModel()

    var body: some View {

        VStack {

            TextField("Enter bill amount", text: $tipViewModel.billAmount)
                .textFieldStyle(RoundedBorderTextFieldStyle())

            Picker(selection: $tipViewModel.tipPercentage, label: Text("Select tip %")) {
                ForEach(tipViewModel.tipChoices, id: \.self) { choice in
                    //Text("\(self.tipViewModel.tipChoices[choice])")
                    Text("\(choice)")
                }
            }.pickerStyle(SegmentedPickerStyle())
                .onTapGesture {
                    self.tipViewModel.calculateTip()
            }
            Text("Tip Percentage \(tipViewModel.tipPercentage)")
            Text(tipViewModel.tipAmount == nil ? "Tip Amount" : "\(tipViewModel.tipAmount!)")
        }.padding()
    }
}

这里是 TipViewModel 文件，

class TipViewModel: ObservableObject {

    @Published var billAmount: String = "" {
        didSet{
            calculateTip()
        }
    }
    @Published var tipPercentage: Int = 10
    @Published var tipAmount: Double = 0

    let tipChoices = [10, 15, 20]

    let didChange = PassthroughSubject<TipViewModel, Never>()

    func calculateTip() {

        guard let billAmount = Double(billAmount) else { return }
        self.tipAmount = billAmount * Double(tipPercentage) / 100
        self.didChange.send(self)
    }
}

任何帮助将不胜感激！

Answer 1

您有一个 onTapGesture 修饰符，它正在吃掉选择器上的点击手势并尝试计算小费。

 .onTapGesture {
                self.tipViewModel.calculateTip()
        }

您可以将tipAmount 计算为计算属性：

struct ContentView: View {

    @ObservedObject var tipViewModel = TipViewModel()

    var body: some View {

        VStack {

            TextField("Enter bill amount", text: $tipViewModel.billAmount)
                .textFieldStyle(RoundedBorderTextFieldStyle())

            Picker(selection: $tipViewModel.tipPercentage, label: Text("Select tip %")) {
                ForEach(tipViewModel.tipChoices, id: \.self) { choice in
                    //Text("\(self.tipViewModel.tipChoices[choice])")
                    Text("\(choice)")
                }
            }.pickerStyle(SegmentedPickerStyle())

            Text("Tip Percentage \(tipViewModel.tipPercentage)")
            Text("\(tipViewModel.tipAmount)")
        }.padding()
    }
}

class TipViewModel: ObservableObject {

    @Published var billAmount: String = ""
    @Published var tipPercentage: Int = 10

    var tipAmount: Double {
        guard let billAmount = Double(billAmount) else { return 0 }
        let tipAmount = billAmount * Double(tipPercentage) / 100
        return tipAmount
    }

    let tipChoices = [10, 15, 20]

}

由于您已经拥有billAmount 和tipPercentage 作为@Published 属性，因此您无需担心向 PassthroughSubject 发送消息来告诉视图在计算属性更改时进行更新。当小费金额或总金额发生变化时，将发送 willChange 消息。这将导致视图刷新，这将调用 tipAmount 计算属性，该属性将运行其闭包并将新值返回给视图。