尝试使工具栏内容有条件并将工具栏移出，如下所示。（现在不可能测试-只是想法）
注：在真实的器械上进行测试

var body: some View {
    VStack {
        Spacer()
        
        TextField("A text field here", text: $str)
            .focused($focusedField, equals: .str)

        TextField("", value: $num, formatter: FloatNumberFormatter())
            .focused($focusedField, equals: .amount)
            .keyboardType(.decimalPad)

        Spacer()
    }
    .toolbar {          // << here !!
        ToolbarItem(placement: .keyboard) {
            if field == .amount {             // << here !!
               Button("Done") {
                  focusedField = nil
               }
            }
        }
    }

}

使用introspect，您可以在View的任何部分执行类似的操作：

.introspectTextField { textField in
                    textField.inputAccessoryView = UIView.getKeyboardToolbar {
                        textField.resignFirstResponder()
                    }
            }

以及对于getKeyboardToolbar：

extension UIView {

static func getKeyboardToolbar( _ callback: @escaping (()->()) ) -> UIToolbar {
        let toolBar = UIToolbar(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: 44))
        let doneButton = CustomBarButtonItem(title: "Done".localized, style: .done) { _ in
            callback()
        }
        
        let space = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        toolBar.items = [space, doneButton]
        
        return toolBar
    }

}

对于CustomBarButtonItem，这是一个条形按钮项，它采用闭包

import UIKit

class CustomBarButtonItem: UIBarButtonItem {
    typealias ActionHandler = (UIBarButtonItem) -> Void

    private var actionHandler: ActionHandler?

    convenience init(image: UIImage?, style: UIBarButtonItem.Style, actionHandler: ActionHandler?) {
        self.init(image: image, style: style, target: nil, action: #selector(barButtonItemPressed(sender:)))
        target = self
        self.actionHandler = actionHandler
    }

    convenience init(title: String?, style: UIBarButtonItem.Style, actionHandler: ActionHandler?) {
        self.init(title: title, style: style, target: nil, action: #selector(barButtonItemPressed(sender:)))
        target = self
        self.actionHandler = actionHandler
    }

    convenience init(barButtonSystemItem systemItem: UIBarButtonItem.SystemItem, actionHandler: ActionHandler?) {
        self.init(barButtonSystemItem: systemItem, target: nil, action: #selector(barButtonItemPressed(sender:)))
        target = self
        self.actionHandler = actionHandler
    }

    @objc func barButtonItemPressed(sender: UIBarButtonItem) {
        actionHandler?(sender)
    }
}

我试了很多次，但最后还是在下面的一个。

.focused($focusedField, equals: .zip)
                .toolbar{
                    ToolbarItem(placement: .keyboard) {
                        switch focusedField{
                        case .zip:
                            HStack{
                                Spacer()
                                Button("Done"){
                                    focusedField = nil
                                }
                            }
                        default:
                                Text("")
                        }
                    }
                }

这就是我的解决方案：

func textFieldSection(title: String,
                      text: Binding<String>,
                      keyboardType: UIKeyboardType,
                      focused: FocusState<Bool>.Binding,
                      required: Bool) -> some View {
    TextField(
        vm.placeholderText(isRequired: required),
        text: text
    )
    .focused(focused)
    .toolbar {
        ToolbarItemGroup(placement: .keyboard) {
            if focused.wrappedValue {
                Spacer()
                Button {
                    focused.wrappedValue = false
                } label: {
                    Text("Done")
                }
            }
        }
    }
}

对于我的项目，我在一个View上有五个TextField视图，所以我在View的扩展中创建了这个方法。
我传递了唯一的FocusState<Bool>.Binding值，并在ToolbarItemGroup闭包中使用它来确定是否应该显示内容（Spacer、Button）。如果特定的TextField是focused，则显示工具栏内容（所有其他非焦点TextField都不会显示）。

我发现将每个TextField Package 在它自己的NavigationView中会给每个TextField提供它自己的上下文，因此会有一个唯一的工具栏。感觉不太对，我在控制台中看到了约束警告。使用如下内容：

var body: some View {
    VStack {
        Spacer()
        
        // I'm not adding .toolbar here...
        NavigationView {
          TextField("A text field here", text: $str)
            .focused($focusedField, equals: .str)
        }
        // I'm only adding .toolbar here, but it still shows for the one above..
        NavigationView {
          TextField("", value: $num, formatter: FloatNumberFormatter())
            .keyboardType(.decimalPad)
            .focused($focusedField, equals: .amount)
            .toolbar {
                ToolbarItem(placement: .keyboard) {
                    Button("Done") {
                        focusedField = nil
                    }
                }
            }
        }
        Spacer()
    }
}

有工作。但其他TextField仍会显示工具列。
--- update ---嗨，我更新了代码以使用ViewModifier，使代码更易于使用，这次代码确实编译并运行〉_〈

struct ToolbarItemWithShow<Toolbar>: ViewModifier where Toolbar: View {
    var show: Bool
    let toolbar: Toolbar
    let placement: ToolbarItemPlacement
    
    func body(content: Content) -> some View {
        content.toolbar {
            ToolbarItemGroup(placement: placement) {
                ZStack(alignment: .leading) {
                    if show {
                        HStack { toolbar }
                            .frame(width: UIScreen.main.bounds.size.width - 12)
                    }
                }
            }
        }
    }
}

extension View {
    func keyboardToolbar<ToolBar>(_ show: Bool, @ViewBuilder toolbar: () -> ToolBar) -> some View where ToolBar: View {
        modifier(ToolbarItemWithShow(show: show, toolbar: toolbar(), placement: .keyboard))
    }
}

struct ContentView: View {
    private enum Field: Hashable {
        case name
        case age
        case gender
    }
    
    @State var name = "Ye"
    @State var age = "14"
    @State var gender = "man"
    
    @FocusState private var focused: Field?

    
    var body: some View {
        VStack {
            TextField("Name", text: $name)
                .focused($focused, equals: .name)
                .keyboardToolbar(focused == .name) {
                    Text("Input Name")
                }
            
            TextField("Age", text: $age)
                .focused($focused, equals: .age)
                .keyboardToolbar(focused == .age) {
                    Text("Input Age")
                }

            TextField("Gender", text: $gender)
                .focused($focused, equals: .gender)
                .keyboardToolbar(focused == .gender) {
                    Text("Input Sex")
                }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

---老---

struct TextFieldWithToolBar<Label, Toolbar>: View where Label: View, Toolbar: View {
    @Binding public var text: String
    public let toolbar: Toolbar?

    @FocusState private var focus: Bool

    var body: some View {
        TextField(text: $text, label: { label })
            .focused($focus)
            .toolbar {
                ToolbarItemGroup(placement: .keyboard) {
                    ZStack(alignment: .leading) {
                        if focus {
                            HStack {
                                toolbar
                                Spacer()
                                Button("Done") {
                                    focus = false
                                }
                            }
                            .frame(width: UIScreen.main.bounds.size.width - 12)
                        }
                    }
                }
            }
    }
}

TextFieldWithToolBar("Name", text: $name)
TextFieldWithToolBar("Name", text: $name){
    Text("Only Brand")
}
TextField("Name", "Set The Name", text: $name)

with Donewith Toolbarwithout