通过 FocusState 修饰键盘消失state

struct ContentView: View {
    @State private var name = ""
    @FocusState private var nameIsFocused: Bool
    var body: some View {
        TextField("input user name", text: $name).focused($nameIsFocused)
        Button("Submit"){
            nameIsFocused = false
        }
    }
}

高级用法通过绑定输入框类型动态调整焦点

struct ContentView: View {
    enum Field {
        case  username
        case  password
        case  confirmedPassword
    }
    @State private var username = ""
    @State private var password = ""

    @FocusState private var focusedField: Field?
    
    var body: some View {
        VStack {
            TextField("username", text: $username)
                .focused($focusedField, equals: .username)
                .textContentType(.givenName)
                .submitLabel(.next)
            TextField("password", text: $password)
                .focused($focusedField, equals: .password)
                .textContentType(.password)
                .submitLabel(.next)
            TextField("confirmed password", text: $password)
                .focused($focusedField, equals: .confirmedPassword)
                .textContentType(.password)
                .submitLabel(.next)
            Button("signup") {
                hideKeyboard()
                
            }
        }
        .onSubmit {
            // 点击键盘的next 调用 onSubmit
            print("focusedField:\(String(describing: focusedField))")
            switch focusedField {
            case .username:
                focusedField = .password
            case .password:
                focusedField = .confirmedPassword
            default:
                hideKeyboard()
            }
        }
    }
}

#if canImport(UIKit)
extension View {
    func hideKeyboard() {
        UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)
    }
}
#endif