样式为DefaultPickerStyle（）的SwiftUI选择器不工作

使用Swift5.2.3、iOS14.4.2、XCode12.4、

在SwiftUI中使用

.sheet

修饰符一开始让我感到兴奋，因为它似乎是一种显示模式表的简单而有效的方法

然而，在现实世界的应用程序中，

.sheet

几乎可以集成

以下是发现的两个bug（除其他外…）：

错误1：当在图纸的分段选择器中时，具有DefaultPickerStyle的选择器不工作

错误2：工作表不会偶尔关闭（）

现在让我们关注Bug Nr1：“当在图纸的分段选择器中时，具有DefaultPickerStyle的选择器不工作”

我的意思可以在这个例子中看到。这是一个真实世界应用程序的摘录。（是的，我需要放置如此多的视图，因为普通教科书的示例工作得非常好——但一旦变得稍微复杂一点就不行了…）

请注意，“可怕的儿童”实际上是

.pickerStyle（DefaultPickerStyle（））

！（您可以在名为

SettingsView

的最底部视图中找到它

如果我用

.pickerStyle（MenuPickerStyle（））

替换该样式，那么应用程序运行得非常好

DefaultPickerStyle（）

有什么问题

请参见以下两个说明问题的视频：

Video-1:FAULT显示

DefaultPickerStyle（）

（您可以看到，

.onChange（of:categoryIndex）{（idx）in…}

从未使用此选择器样式调用过…）

视频-2：正确显示

MenuPickerStyle（）

ContentView如下所示：

enum THSheetSelection: Hashable, Identifiable {        
    case infoSettings
    var id: THSheetSelection { self }
}

struct ContentView: View {
    
    @State var sheetState: THSheetSelection?
    
    var body: some View {
        VStack {
            Text("Hello, world!")
                .padding()
            Button("Show Settings Sheet") {
                sheetState = .infoSettings
            }
        }
        .sheet(item: $sheetState) { state in
            switch state {
            case .infoSettings:
                InfoSettingsView()
            }
        }
    }
}

struct InfoSettingsView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    @State private var segmentSelection = 0
    @State private var infoShown = false
    
    var body: some View {
        
        NavigationView {
            
            VStack {
                Picker("", selection: $segmentSelection) {
                    Text("Info").tag(0)
                    Text("Settiongs").tag(1)
                }
                .pickerStyle(SegmentedPickerStyle())
                .background(Color.blue)
                .padding()
                
                switch segmentSelection {
                case 0:
                    InfoView()
                case 1:
                    SettingsView()
                default:
                    InfoView()
                }
            }
            .navigationBarTitle("Info & Settings")
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button(action: {
                        presentationMode.wrappedValue.dismiss()
                    }) {
                        Text("Done")
                    }
                }
            }
            .onAppear {
                segmentSelection = 0
            }
        }
    }
}

struct InfoView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    let versionNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String) ?? ""
    let buildNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String) ?? ""
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text("App Info")) {
                    HStack {
                        Text("App Version")
                        Spacer()
                        Text("v\(versionNr) (\(buildNr))")
                    }
                }
            }
            .ignoresSafeArea()
            
            Spacer()
        }
    }
}

struct SettingsView: View {
        
    @State private var categoryIndex = 0
    var categorySelection = ["Choice 1", "Choice 2", "Choice 3", "Choice 4"]
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text(LocalizedStringKey("InterDeviceCommKey"))) {
                    Picker(selection: $categoryIndex, label: Text(LocalizedStringKey("TechChoiceKey"))) {
                        ForEach(0 ..< categorySelection.count, id: \.self) { idx in
                            Text(categorySelection[idx]).tag(idx)
                        }
                    }
                    .pickerStyle(DefaultPickerStyle()) // does NOT behave correctly
                    // .pickerStyle(MenuPickerStyle()) // does behave correctly
                    .onChange(of: categoryIndex) { (idx) in  /// ????????? why this never gets called with DefaultPickerStyle() ?????????
                        print("categoryChanged to index \(idx)")
                    }
                }
                Section(header: Text("Selected Choice")) {
                    HStack {
                        Text("My choice")
                        Spacer()
                        Text("\(categorySelection[categoryIndex])")
                    }
                }
                .ignoresSafeArea()
            }            
            Spacer()
        }
    }
}

信息设置视图如下所示：

enum THSheetSelection: Hashable, Identifiable {        
    case infoSettings
    var id: THSheetSelection { self }
}

struct ContentView: View {
    
    @State var sheetState: THSheetSelection?
    
    var body: some View {
        VStack {
            Text("Hello, world!")
                .padding()
            Button("Show Settings Sheet") {
                sheetState = .infoSettings
            }
        }
        .sheet(item: $sheetState) { state in
            switch state {
            case .infoSettings:
                InfoSettingsView()
            }
        }
    }
}

struct InfoSettingsView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    @State private var segmentSelection = 0
    @State private var infoShown = false
    
    var body: some View {
        
        NavigationView {
            
            VStack {
                Picker("", selection: $segmentSelection) {
                    Text("Info").tag(0)
                    Text("Settiongs").tag(1)
                }
                .pickerStyle(SegmentedPickerStyle())
                .background(Color.blue)
                .padding()
                
                switch segmentSelection {
                case 0:
                    InfoView()
                case 1:
                    SettingsView()
                default:
                    InfoView()
                }
            }
            .navigationBarTitle("Info & Settings")
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button(action: {
                        presentationMode.wrappedValue.dismiss()
                    }) {
                        Text("Done")
                    }
                }
            }
            .onAppear {
                segmentSelection = 0
            }
        }
    }
}

struct InfoView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    let versionNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String) ?? ""
    let buildNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String) ?? ""
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text("App Info")) {
                    HStack {
                        Text("App Version")
                        Spacer()
                        Text("v\(versionNr) (\(buildNr))")
                    }
                }
            }
            .ignoresSafeArea()
            
            Spacer()
        }
    }
}

struct SettingsView: View {
        
    @State private var categoryIndex = 0
    var categorySelection = ["Choice 1", "Choice 2", "Choice 3", "Choice 4"]
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text(LocalizedStringKey("InterDeviceCommKey"))) {
                    Picker(selection: $categoryIndex, label: Text(LocalizedStringKey("TechChoiceKey"))) {
                        ForEach(0 ..< categorySelection.count, id: \.self) { idx in
                            Text(categorySelection[idx]).tag(idx)
                        }
                    }
                    .pickerStyle(DefaultPickerStyle()) // does NOT behave correctly
                    // .pickerStyle(MenuPickerStyle()) // does behave correctly
                    .onChange(of: categoryIndex) { (idx) in  /// ????????? why this never gets called with DefaultPickerStyle() ?????????
                        print("categoryChanged to index \(idx)")
                    }
                }
                Section(header: Text("Selected Choice")) {
                    HStack {
                        Text("My choice")
                        Spacer()
                        Text("\(categorySelection[categoryIndex])")
                    }
                }
                .ignoresSafeArea()
            }            
            Spacer()
        }
    }
}

InfoView如下所示：

enum THSheetSelection: Hashable, Identifiable {        
    case infoSettings
    var id: THSheetSelection { self }
}

struct ContentView: View {
    
    @State var sheetState: THSheetSelection?
    
    var body: some View {
        VStack {
            Text("Hello, world!")
                .padding()
            Button("Show Settings Sheet") {
                sheetState = .infoSettings
            }
        }
        .sheet(item: $sheetState) { state in
            switch state {
            case .infoSettings:
                InfoSettingsView()
            }
        }
    }
}

struct InfoSettingsView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    @State private var segmentSelection = 0
    @State private var infoShown = false
    
    var body: some View {
        
        NavigationView {
            
            VStack {
                Picker("", selection: $segmentSelection) {
                    Text("Info").tag(0)
                    Text("Settiongs").tag(1)
                }
                .pickerStyle(SegmentedPickerStyle())
                .background(Color.blue)
                .padding()
                
                switch segmentSelection {
                case 0:
                    InfoView()
                case 1:
                    SettingsView()
                default:
                    InfoView()
                }
            }
            .navigationBarTitle("Info & Settings")
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button(action: {
                        presentationMode.wrappedValue.dismiss()
                    }) {
                        Text("Done")
                    }
                }
            }
            .onAppear {
                segmentSelection = 0
            }
        }
    }
}

struct InfoView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    let versionNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String) ?? ""
    let buildNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String) ?? ""
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text("App Info")) {
                    HStack {
                        Text("App Version")
                        Spacer()
                        Text("v\(versionNr) (\(buildNr))")
                    }
                }
            }
            .ignoresSafeArea()
            
            Spacer()
        }
    }
}

struct SettingsView: View {
        
    @State private var categoryIndex = 0
    var categorySelection = ["Choice 1", "Choice 2", "Choice 3", "Choice 4"]
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text(LocalizedStringKey("InterDeviceCommKey"))) {
                    Picker(selection: $categoryIndex, label: Text(LocalizedStringKey("TechChoiceKey"))) {
                        ForEach(0 ..< categorySelection.count, id: \.self) { idx in
                            Text(categorySelection[idx]).tag(idx)
                        }
                    }
                    .pickerStyle(DefaultPickerStyle()) // does NOT behave correctly
                    // .pickerStyle(MenuPickerStyle()) // does behave correctly
                    .onChange(of: categoryIndex) { (idx) in  /// ????????? why this never gets called with DefaultPickerStyle() ?????????
                        print("categoryChanged to index \(idx)")
                    }
                }
                Section(header: Text("Selected Choice")) {
                    HStack {
                        Text("My choice")
                        Spacer()
                        Text("\(categorySelection[categoryIndex])")
                    }
                }
                .ignoresSafeArea()
            }            
            Spacer()
        }
    }
}

设置视图如下所示：

enum THSheetSelection: Hashable, Identifiable {        
    case infoSettings
    var id: THSheetSelection { self }
}

struct ContentView: View {
    
    @State var sheetState: THSheetSelection?
    
    var body: some View {
        VStack {
            Text("Hello, world!")
                .padding()
            Button("Show Settings Sheet") {
                sheetState = .infoSettings
            }
        }
        .sheet(item: $sheetState) { state in
            switch state {
            case .infoSettings:
                InfoSettingsView()
            }
        }
    }
}

struct InfoSettingsView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    @State private var segmentSelection = 0
    @State private var infoShown = false
    
    var body: some View {
        
        NavigationView {
            
            VStack {
                Picker("", selection: $segmentSelection) {
                    Text("Info").tag(0)
                    Text("Settiongs").tag(1)
                }
                .pickerStyle(SegmentedPickerStyle())
                .background(Color.blue)
                .padding()
                
                switch segmentSelection {
                case 0:
                    InfoView()
                case 1:
                    SettingsView()
                default:
                    InfoView()
                }
            }
            .navigationBarTitle("Info & Settings")
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button(action: {
                        presentationMode.wrappedValue.dismiss()
                    }) {
                        Text("Done")
                    }
                }
            }
            .onAppear {
                segmentSelection = 0
            }
        }
    }
}

struct InfoView: View {
    
    @Environment(\.presentationMode) var presentationMode
    
    let versionNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String) ?? ""
    let buildNr: String = (Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String) ?? ""
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text("App Info")) {
                    HStack {
                        Text("App Version")
                        Spacer()
                        Text("v\(versionNr) (\(buildNr))")
                    }
                }
            }
            .ignoresSafeArea()
            
            Spacer()
        }
    }
}

struct SettingsView: View {
        
    @State private var categoryIndex = 0
    var categorySelection = ["Choice 1", "Choice 2", "Choice 3", "Choice 4"]
    
    var body: some View {
        
        VStack {
            Form {
                Section(header: Text(LocalizedStringKey("InterDeviceCommKey"))) {
                    Picker(selection: $categoryIndex, label: Text(LocalizedStringKey("TechChoiceKey"))) {
                        ForEach(0 ..< categorySelection.count, id: \.self) { idx in
                            Text(categorySelection[idx]).tag(idx)
                        }
                    }
                    .pickerStyle(DefaultPickerStyle()) // does NOT behave correctly
                    // .pickerStyle(MenuPickerStyle()) // does behave correctly
                    .onChange(of: categoryIndex) { (idx) in  /// ????????? why this never gets called with DefaultPickerStyle() ?????????
                        print("categoryChanged to index \(idx)")
                    }
                }
                Section(header: Text("Selected Choice")) {
                    HStack {
                        Text("My choice")
                        Spacer()
                        Text("\(categorySelection[categoryIndex])")
                    }
                }
                .ignoresSafeArea()
            }            
            Spacer()
        }
    }
}

结构设置视图：视图{ @国家私有变量类别索引=0 变量类别选择=[“选择1”、“选择2”、“选择3”、“选择4”] var body：一些观点{ VStack{ 形式{ 节（标题：文本（LocalizedStringKey（“InterDeviceCommKey”））{ 选择器（选择：$categoryIndex，标签：文本（LocalizedStringKey（“TechChoiceKey”））{ ForEach（0.. 你知道为什么SwiftUI

.sheet

的DefaultPickerStyle（）在上述情况下不能正常工作吗