SwiftUI中Alert弹窗内Picker组件不显示问题求助

SwiftUI的Alert组件对内部可嵌入的视图类型有严格限制，它仅支持TextField、Button这类基础交互控件，像你用的带.menu样式的Picker和.graphical样式的DatePicker并不在Alert的支持范围内，这就是它们不显示的原因。

下面给你两种可行的解决办法：

方法一：使用ConfirmationDialog替代Alert #

ConfirmationDialog是专门用于展示包含更多选择项的弹窗，支持嵌入Picker这类控件，用法和Alert类似：

struct ProjectsView: View {
    @State private var date = Date()
    @State private var project = ""
    @State private var user = ""
    let userList = ["Tom", "Anna", "Mike"]
    @State private var showingDialog = false // 替换原有的showingMessage
    
    var body: some View {
        NavigationStack {
            VStack {
                createBtn
            }
        }
    }
    
    private extension ProjectsView {
        var createBtn: some View {
            Button(action: { showingDialog = true }){
                Text("Add project")
            }
            .confirmationDialog("Add project", isPresented: $showingDialog) {
                TextField("Project", text: $project)
                
                Picker(selection: $user, label: Text("User")) {
                    ForEach(userList, id: \.self) {
                        Text($0)
                    }
                }
                .pickerStyle(.menu)
                
                DatePicker("Date", selection: $date, displayedComponents: [.date])
                    .datePickerStyle(.graphical)
                
                Button("Save", action: saveProject)
                Button("Cancel", role: .cancel) {}
            } message: {
                Text("Fill in project details")
            }
        }
        
        func saveProject() {
            // 在这里编写你的保存逻辑
        }
    }
}

方法二：使用Sheet自定义弹窗 #

如果需要更自由的布局样式，完全自定义弹窗内容，推荐用Sheet：

struct ProjectsView: View {
    @State private var date = Date()
    @State private var project = ""
    @State private var user = ""
    let userList = ["Tom", "Anna", "Mike"]
    @State private var showingSheet = false
    
    var body: some View {
        NavigationStack {
            VStack {
                createBtn
            }
            .sheet(isPresented: $showingSheet) {
                // 自定义弹窗内容
                NavigationStack {
                    VStack(spacing: 20) {
                        TextField("Project", text: $project)
                            .textFieldStyle(.roundedBorder)
                        
                        Picker(selection: $user, label: Text("User")) {
                            ForEach(userList, id: \.self) {
                                Text($0)
                            }
                        }
                        .pickerStyle(.menu)
                        .padding()
                        
                        DatePicker("Date", selection: $date, displayedComponents: [.date])
                            .datePickerStyle(.graphical)
                        
                        HStack {
                            Button("Cancel", role: .cancel) {
                                showingSheet = false
                            }
                            .buttonStyle(.bordered)
                            
                            Button("Save") {
                                saveProject()
                                showingSheet = false
                            }
                            .buttonStyle(.borderedProminent)
                        }
                    }
                    .padding()
                    .navigationTitle("Add project")
                    .toolbar {
                        ToolbarItem(placement: .cancellationAction) {
                            Button("Cancel") { showingSheet = false }
                        }
                        ToolbarItem(placement: .confirmationAction) {
                            Button("Save") {
                                saveProject()
                                showingSheet = false
                            }
                        }
                    }
                }
            }
        }
    }
    
    private extension ProjectsView {
        var createBtn: some View {
            Button(action: { showingSheet = true }){
                Text("Add project")
            }
        }
        
        func saveProject() {
            // 编写保存逻辑
        }
    }
}

注：你的原代码缺少showingMessage的@State定义和saveProject函数实现，上述示例已补充这些内容。

内容的提问来源于stack exchange，提问作者Der_Knappe