SwiftUI：显示警报时如何摆脱分段控制文本移动？

Question

在一个小示例 SwiftUI 应用程序中，我有一个设置视图，显示几个选项选择，实现为分段控件。当出现或解除警报时，这些分段控件中的文本会明显移动。有没有办法消除这个故障？

将此粘贴到 Playground 中以重现：

import SwiftUI
import PlaygroundSupport

struct FlickeringSegmentsView: View {
    @State var option = 0
    @State var alerting = false

    var body: some View {
        VStack(alignment: .center, spacing: 120) {
            Picker("options", selection: $option) {
                Text("Option A").tag(0)
                Text("Option B").tag(1)
            }
            .pickerStyle(SegmentedPickerStyle())
            .padding(16)

            Button(action: { self.alerting.toggle() },
                   label: { Text("Show Alert") }
            )
            .alert(isPresented: $alerting) {
                Alert(title: Text("Alert"))
            }
        }
    }
}

PlaygroundPage.current.setLiveView(FlickeringSegmentsView())

Answer 1

希望下面的代码对您有所帮助：

public protocol SegmentedPickerViewElementTraits: Hashable {
    var localizedText: String { get }
}

public struct SegmentedPickerView<Value, Data, ID, Label>: View
    where
    Value: SegmentedPickerViewElementTraits,
    Data: RandomAccessCollection,
    Data.Element == Value,
    ID: Hashable,
    Label: View {

    public let data: Data
    public let id: KeyPath<Data.Element, ID>
    public let selection: Binding<Value>
    public let label: Label

    public init(data: Data,
                id: KeyPath<Data.Element, ID>,
                selection: Binding<Value>,
                label: Label) {
        self.data = data
        self.id = id
        self.selection = selection
        self.label = label
    }

    public var body: some View {
        Picker(selection: selection, label: label) {
            ForEach(data, id: id) {
                Text([=10=].localizedText).tag([=10=])
            }
        }
        .pickerStyle(SegmentedPickerStyle())
    }
}

然后让我们修改您的代码：

enum Options: UInt8, CaseIterable {
    case optionA
    case optionB
}

extension Options: SegmentedPickerViewElementTraits {
    var localizedText: String {
        switch self {
        case .optionA:
            return "Option A"
        case .optionB:
            return "Option B"
        }
    }
}

struct FlickeringSegmentsView: View {
    @State
    var option: Options = .optionA

    @State
    var alerting = false

    var body: some View {
        VStack(alignment: .center, spacing: 120) {
            SegmentedPickerView(
                data: Options.allCases,
                id: \.self,
                selection: $option,
                label: Text("options")
            )
            .padding(16)

            Button(
                action: { self.alerting.toggle() },
                label: { Text("Show Alert") }
            )
            .alert(isPresented: $alerting) {
                Alert(title: Text("Alert"))
            }
        }
    }
}

Answer 2

此问题已在 Xcode 12 测试版中使用随附的 iOS 14 模拟器解决（希望保持这种状态）。

SwiftUI：显示警报时如何摆脱分段控制文本移动？

SwiftUI: how to get rid of Segmented Control text movement when an alert is shown?

swiftui

uisegmentedcontrol