如何移动到 SwiftUI 中的下一个 TextField？

Question

使用 Swift5.1.2, iOS13.2, Xcode-11.2,

在 Stackview 中有几个 TextField，我想在用户在第一个 TextField 中键入 x 数量的字符后立即移动到下一个 TextField。

通过此链接，我可以识别 TextField 条目何时达到 x 字符数。但是，我不知道如何让 firstResponder 跳转到我的 StackView 中的第二个 TextField。

SwiftUI 有解决方案吗？

Answer 1

使用 iOS 15+ @FocusState - 通用解决方案

用法示例：

@FocusState private var focusedField: Field?
enum Field: Int, Hashable {
   case name
   case country
   case city
}

var body: some View {
    TextField(text: $name)
        .focused($focusedField, equals: .name)
        .onSubmit { self.focusNextField($focusedField) }
// ...

代码：

extension View {
    /// Focuses next field in sequence, from the given `FocusState`.
    /// Requires a currently active focus state and a next field available in the sequence.
    ///
    /// Example usage:
    /// ```
    /// .onSubmit { self.focusNextField($focusedField) }
    /// ```
    /// Given that `focusField` is an enum that represents the focusable fields. For example:
    /// ```
    /// @FocusState private var focusedField: Field?
    /// enum Field: Int, Hashable {
    ///    case name
    ///    case country
    ///    case city
    /// }
    /// ```
    func focusNextField<F: RawRepresentable>(_ field: FocusState<F?>.Binding) where F.RawValue == Int {
        guard let currentValue = field.wrappedValue else { return }
        let nextValue = currentValue.rawValue + 1
        if let newValue = F.init(rawValue: nextValue) {
            field.wrappedValue = newValue
        }
    }

    /// Focuses previous field in sequence, from the given `FocusState`.
    /// Requires a currently active focus state and a previous field available in the sequence.
    ///
    /// Example usage:
    /// ```
    /// .onSubmit { self.focusNextField($focusedField) }
    /// ```
    /// Given that `focusField` is an enum that represents the focusable fields. For example:
    /// ```
    /// @FocusState private var focusedField: Field?
    /// enum Field: Int, Hashable {
    ///    case name
    ///    case country
    ///    case city
    /// }
    /// ```
    func focusPreviousField<F: RawRepresentable>(_ field: FocusState<F?>.Binding) where F.RawValue == Int {
        guard let currentValue = field.wrappedValue else { return }
        let nextValue = currentValue.rawValue - 1
        if let newValue = F.init(rawValue: nextValue) {
            field.wrappedValue = newValue
        }
    }
}

Answer 2

iOS 15+

使用@FocusState

iOS 15 之前

我已经接受了@Philip Borbon 的回答并对其进行了一些清理。我删除了很多自定义内容，并将其保留在最低限度，以便更容易地看到需要什么。

struct CustomTextfield: UIViewRepresentable {
    let label: String
    @Binding var text: String
    
    var focusable: Binding<[Bool]>? = nil
    
    var returnKeyType: UIReturnKeyType = .default
    
    var tag: Int? = nil
    
    var onCommit: (() -> Void)? = nil
    
    func makeUIView(context: Context) -> UITextField {
        let textField = UITextField(frame: .zero)
        textField.placeholder = label
        textField.delegate = context.coordinator
        
        textField.returnKeyType = returnKeyType
        
        if let tag = tag {
            textField.tag = tag
        }
        
        return textField
    }
    
    func updateUIView(_ uiView: UITextField, context: Context) {
        uiView.text = text
        
        if let focusable = focusable?.wrappedValue {
            var resignResponder = true
            
            for (index, focused) in focusable.enumerated() {
                if uiView.tag == index && focused {
                    uiView.becomeFirstResponder()
                    resignResponder = false
                    break
                }
            }
            
            if resignResponder {
                uiView.resignFirstResponder()
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    final class Coordinator: NSObject, UITextFieldDelegate {
        let parent: CustomTextfield
        
        init(_ parent: CustomTextfield) {
            self.parent = parent
        }
        
        func textFieldDidBeginEditing(_ textField: UITextField) {
            guard var focusable = parent.focusable?.wrappedValue else { return }
            
            for i in 0...(focusable.count - 1) {
                focusable[i] = (textField.tag == i)
            }
            parent.focusable?.wrappedValue = focusable
        }
        
        func textFieldShouldReturn(_ textField: UITextField) -> Bool {
            guard var focusable = parent.focusable?.wrappedValue else {
                textField.resignFirstResponder()
                return true
            }
            
            for i in 0...(focusable.count - 1) {
                focusable[i] = (textField.tag + 1 == i)
            }
            
            parent.focusable?.wrappedValue = focusable
            
            if textField.tag == focusable.count - 1 {
                textField.resignFirstResponder()
            }
            
            return true
        }
        
        @objc func textFieldDidChange(_ textField: UITextField) {
            parent.text = textField.text ?? ""
        }
    }
}

Answer 3

我正在使用UITextField并UIViewRepresentable实现这一目标。

定义tag每个文本字段并声明一个布尔值列表，该列表具有相同数量的可用文本字段以关注返回键，fieldFocus，这将跟踪基于当前索引/标签的下一个要关注的文本字段。

用法：

import SwiftUI

struct Sample: View {
    @State var firstName: String = ""
    @State var lastName: String = ""
    
    @State var fieldFocus = [false, false]
    
    var body: some View {
        VStack {
            KitTextField (
                label: "First name",
                text: $firstName,
                focusable: $fieldFocus,
                returnKeyType: .next,
                tag: 0
            )
            .padding()
            .frame(height: 48)
            
            KitTextField (
                label: "Last name",
                text: $lastName,
                focusable: $fieldFocus,
                returnKeyType: .done,
                tag: 1
            )
            .padding()
            .frame(height: 48)
        }
    }
}

UITextField在UIViewRepresentable：

import SwiftUI

struct KitTextField: UIViewRepresentable {
    let label: String
    @Binding var text: String
    
    var focusable: Binding<[Bool]>? = nil
    var isSecureTextEntry: Binding<Bool>? = nil
    
    var returnKeyType: UIReturnKeyType = .default
    var autocapitalizationType: UITextAutocapitalizationType = .none
    var keyboardType: UIKeyboardType = .default
    var textContentType: UITextContentType? = nil
    
    var tag: Int? = nil
    var inputAccessoryView: UIToolbar? = nil
    
    var onCommit: (() -> Void)? = nil
    
    func makeUIView(context: Context) -> UITextField {
        let textField = UITextField(frame: .zero)
        textField.delegate = context.coordinator
        textField.placeholder = label
        
        textField.returnKeyType = returnKeyType
        textField.autocapitalizationType = autocapitalizationType
        textField.keyboardType = keyboardType
        textField.isSecureTextEntry = isSecureTextEntry?.wrappedValue ?? false
        textField.textContentType = textContentType
        textField.textAlignment = .left
        
        if let tag = tag {
            textField.tag = tag
        }
        
        textField.inputAccessoryView = inputAccessoryView
        textField.addTarget(context.coordinator, action: #selector(Coordinator.textFieldDidChange(_:)), for: .editingChanged)
        
        textField.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        
        return textField
    }
    
    func updateUIView(_ uiView: UITextField, context: Context) {
        uiView.text = text
        uiView.isSecureTextEntry = isSecureTextEntry?.wrappedValue ?? false
        
        if let focusable = focusable?.wrappedValue {
            var resignResponder = true
            
            for (index, focused) in focusable.enumerated() {
                if uiView.tag == index && focused {
                    uiView.becomeFirstResponder()
                    resignResponder = false
                    break
                }
            }
            
            if resignResponder {
                uiView.resignFirstResponder()
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    final class Coordinator: NSObject, UITextFieldDelegate {
        let control: KitTextField
        
        init(_ control: KitTextField) {
            self.control = control
        }
        
        func textFieldDidBeginEditing(_ textField: UITextField) {
            guard var focusable = control.focusable?.wrappedValue else { return }
            
            for i in 0...(focusable.count - 1) {
                focusable[i] = (textField.tag == i)
            }
            
            control.focusable?.wrappedValue = focusable
        }
        
        func textFieldShouldReturn(_ textField: UITextField) -> Bool {
            guard var focusable = control.focusable?.wrappedValue else {
                textField.resignFirstResponder()
                return true
            }
            
            for i in 0...(focusable.count - 1) {
                focusable[i] = (textField.tag + 1 == i)
            }
            
            control.focusable?.wrappedValue = focusable
            
            if textField.tag == focusable.count - 1 {
                textField.resignFirstResponder()
            }
            
            return true
        }
        
        func textFieldDidEndEditing(_ textField: UITextField) {
            control.onCommit?()
        }
        
        @objc func textFieldDidChange(_ textField: UITextField) {
            control.text = textField.text ?? ""
        }
    }
}

Answer 4

iOS 15+

在 iOS 15 中，我们现在可以用来@FocusState控制应该关注哪个字段。

这是一个演示：

struct ContentView: View {
    @State private var street: String = ""
    @State private var city: String = ""
    @State private var country: String = ""

    @FocusState private var focusedField: Field?

    var body: some View {
        NavigationView {
            VStack {
                TextField("Street", text: $street)
                    .focused($focusedField, equals: .street)
                TextField("City", text: $city)
                    .focused($focusedField, equals: .city)
                TextField("Country", text: $country)
                    .focused($focusedField, equals: .country)
            }
            .toolbar {
                ToolbarItem(placement: .keyboard) {
                    Button(action: focusPreviousField) {
                        Image(systemName: "chevron.up")
                    }
                    .disabled(!canFocusPreviousField()) // remove this to loop through fields
                }
                ToolbarItem(placement: .keyboard) {
                    Button(action: focusNextField) {
                        Image(systemName: "chevron.down")
                    }
                    .disabled(!canFocusNextField()) // remove this to loop through fields
                }
            }
        }
    }
}

extension ContentView {
    private enum Field: Int, CaseIterable {
        case street, city, country
    }
    
    private func focusPreviousField() {
        focusedField = focusedField.map {
            Field(rawValue: $0.rawValue - 1) ?? .country
        }
    }

    private func focusNextField() {
        focusedField = focusedField.map {
            Field(rawValue: $0.rawValue + 1) ?? .street
        }
    }
    
    private func canFocusPreviousField() -> Bool {
        guard let currentFocusedField = focusedField else {
            return false
        }
        return currentFocusedField.rawValue > 0
    }

    private func canFocusNextField() -> Bool {
        guard let currentFocusedField = focusedField else {
            return false
        }
        return currentFocusedField.rawValue < Field.allCases.count - 1
    }
}

Answer 5

尝试这个：

import SwiftUI

struct ResponderTextField: UIViewRepresentable {

    typealias TheUIView = UITextField
    var isFirstResponder: Bool
    var configuration = { (view: TheUIView) in }

    func makeUIView(context: UIViewRepresentableContext<Self>) -> TheUIView { TheUIView() }
    func updateUIView(_ uiView: TheUIView, context: UIViewRepresentableContext<Self>) {
        _ = isFirstResponder ? uiView.becomeFirstResponder() : uiView.resignFirstResponder()
        configuration(uiView)
    }
}


struct ContentView: View {
    @State private var entry = ""
    @State private var entry2 = ""

    let characterLimit = 6

    var body: some View {
        VStack {
            TextField("hallo", text: $entry)
                .disabled(entry.count > (characterLimit - 1))

            ResponderTextField(isFirstResponder: entry.count > (characterLimit - 1)) { uiView in
                uiView.placeholder = "2nd textField"
            }
        }
    }
}

Answer 6

iOS 15

今年，苹果推出了一个新的修饰符以及一个名为@FocusState控制键盘和焦点键盘状态的新包装器（“又名”firstResponder）。

以下是如何迭代文本字段的示例：

另外，您可以查看此答案，了解如何创建文本字段第一响应者或放弃它以隐藏键盘，并了解有关如何将此枚举绑定到文本字段的更多信息。