Ios 如何将后续文本添加到uitextfield

我有一个带有占位符的文本字段，名为

letschat

。现在，每当我开始在文本字段中键入内容时，我都希望将文本字段显示为

some@letschat

。当我的文本字段为空时，必须显示占位符。我做到了。但我想在我开始输入文本字段时设置。无论我用什么输入，我都希望此文本也可见，如：

一些@Lletschat

---

我如何才能做到这一点？

使您的类符合

UITextfieldDelegate

，然后分配

textfield.delegate=self

现在，如果希望在用户结束键入后追加@letschat，请添加此委托方法

func textFieldDidEndEditing(textField: UITextField) {
    textField.text = "\(textField.text)@letschat"
}

或者如果你在打字的时候想要它

textField.addTarget(self, action: #selector(YourViewController.textFieldDidChange(_:)), forControlEvents: UIControlEvents.EditingChanged)

func textFieldDidChange(textField: UITextField) {
    if textField.containsString("@letschat")  {
        textField.text = textField.text.stringByReplacingOccurrencesOfString("@letschat", withString: "")
    }

    textField.text = "\(textField.text)@letschat"

}

希望这对您有所帮助。

您可以使用

UITextField

textfielddichange

的函数，并在每次文本字段文本更改时获得调用

就这样：

func textChangedAction(sender:UITextFiled) {
   if sender.text.rangeOfString("@Lletschat") != nil{ 
       sender.text = sender.text.replacingOccurrences(of: "@Lletschat", with: "")  
   }
   sender.text = "\(sender.text!) @Lletschat"
}

---

如果要更改特定文本的颜色，可以进行检查。

像这样实现textfield委托-

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    textField.text = textField.text?.replacingOccurrences(of: " @\(textField.placeholder!)", with: "", options: .literal, range: nil)
    textField.text?.append(string)
    textField.text?.append(" @\(textField.placeholder!)")

    return false
}

简单解决方案：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard let newRange = textField.text?.range(from: range), let result = textField.text?.replacingCharacters(in: newRange, with: string) else { return true }
    if result.endsWithString("@letschat") {
        return true
    } else {
        textField.text = result + "@letschat"
        let position = textField.position(from: textField.beginningOfDocument, offset: result.characters.count)!
        textField.selectedTextRange = textField.textRange(from: position, to: position)
        return false
    }
}

使用辅助程序扩展：

extension String {

    func range(from oldOne: NSRange) -> Range<String.Index>? {
        guard
            let from16 = utf16.index(utf16.startIndex, offsetBy: oldOne.location, limitedBy: utf16.endIndex),
            let to16 = utf16.index(utf16.startIndex, offsetBy: oldOne.location + oldOne.length, limitedBy: utf16.endIndex),
            let from = from16.samePosition(in: self),
            let to = to16.samePosition(in: self)
            else { return nil }
        return from ..< to
    }

    func endsWithString(_ string: String) -> Bool {
        guard characters.count >= string.characters.count else { return false }
        let index = self.index(startIndex, offsetBy: characters.count - string.characters.count)
        let substring = self.substring(from: index)
        return substring == string
    }
}

使用“自动布局”可使其之间保持3个像素的距离。

---

别忘了将类配置为将所有传入操作发送到textfield。您可以为这些控件使用不同的字体颜色，这样用户就不会对更改标签值的操作感到困惑。

我创建了一个

UITextField

子类，它使用占位符（如果设置）作为后缀。据我所知，一切正常。也许有一些调整需要满足您的需要

如果有任何不清楚的地方，请随时询问：

class SuffixTextField: UITextField {

    override init(frame: CGRect) {
        super.init(frame: frame)
        sharedInit()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        sharedInit()
    }

    private func sharedInit() {
        addTarget(self, action: #selector(textChanged), for: .editingChanged)
    }

    override var text: String? {
        didSet {
            selectedTextRange = maxTextRange
        }
    }

    override var attributedText: NSAttributedString? {
        didSet {
            selectedTextRange = maxTextRange
        }
    }

    @objc private func textChanged() {
        if let currentText = text, let placeholder = placeholder {
            if currentText == placeholder {
                self.text = nil
            } else if !currentText.hasSuffix(placeholder) {
                self.text = currentText + placeholder
            }
        }
    }

    private var maxCursorPosition: UITextPosition? {
        guard let placeholder = placeholder, !placeholder.isEmpty else { return nil }
        guard let text = text, !text.isEmpty else { return nil }
        return position(from: beginningOfDocument, offset: (text as NSString).range(of: placeholder, options: .backwards).location)
    }

    private var maxTextRange: UITextRange? {
        guard let maxCursorPosition = maxCursorPosition else { return nil }
        return textRange(from: maxCursorPosition, to: maxCursorPosition)
    }

    override var selectedTextRange: UITextRange? {
        get { return super.selectedTextRange }
        set {
            guard let newRange = newValue,
                let maxCursorPosition = maxCursorPosition else {
                    super.selectedTextRange = newValue
                    return
            }

            if compare(maxCursorPosition, to: newRange.start) == .orderedAscending {
                super.selectedTextRange = textRange(from: maxCursorPosition, to: maxCursorPosition)
            } else if compare(maxCursorPosition, to: newRange.end) == .orderedAscending {
                super.selectedTextRange = textRange(from: newRange.start, to: maxCursorPosition)
            } else {
                super.selectedTextRange = newValue
            }
        }
    }

}

您可以在此处看到预览：

---

您希望此文本显示在何处？在键入的字段下？@Astoria是的……我是说……当我完成键入文本字段时，如果文本字段中没有文本。此时，我的占位符将显示……当我开始键入占位符时，我应该隐藏……如果我键入

a

。那么我将自动看到类似

a@letschat

。如果我键入更多类似

adasd@letschat

必须在文本字段中可见此设置文本后将调用。您没有收到“@letschat@letschat@letschat“在输入了几个字符之后？它不是那样工作的

didBeginEditing

在字段成为第一响应者时调用。@Astoria.Ya这是它的工作。但是一旦我开始编辑它的显示，这很好。但是当我取消所有文本并且没有文本时，我的意思是文本字段中甚至没有一个字母。然后我的占位符必须显示。但是现在仍然显示了“@letschat”。我怎样才能达到目标that@doubtman如果结果==“@letschat”{//set nil value并返回false}和“@letschat”shoyld不可编辑，请尝试使用

。我再次将标记放在“@letschat”的后面，还有一个“@letschat”也在添加，而且我也尝试了这个…
如果结果==“@letschat”{textField.text=”“return false}
当textField中没有值时。仍然是“@letschat”当你肯定需要实施困难的解决方案时，因为有太多的
if
案例。我使用了带有占位符值的代码解决方案。但它根本没有反映…你能分享代码吗？这样，就不会有更多的代码了。您只需以编程方式创建一个
subfixtfield
，或者在故事板中添加一个textfield，并将其自定义类设置为
subfixtfield
。
class SuffixTextField: UITextField {

    override init(frame: CGRect) {
        super.init(frame: frame)
        sharedInit()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        sharedInit()
    }

    private func sharedInit() {
        addTarget(self, action: #selector(textChanged), for: .editingChanged)
    }

    override var text: String? {
        didSet {
            selectedTextRange = maxTextRange
        }
    }

    override var attributedText: NSAttributedString? {
        didSet {
            selectedTextRange = maxTextRange
        }
    }

    @objc private func textChanged() {
        if let currentText = text, let placeholder = placeholder {
            if currentText == placeholder {
                self.text = nil
            } else if !currentText.hasSuffix(placeholder) {
                self.text = currentText + placeholder
            }
        }
    }

    private var maxCursorPosition: UITextPosition? {
        guard let placeholder = placeholder, !placeholder.isEmpty else { return nil }
        guard let text = text, !text.isEmpty else { return nil }
        return position(from: beginningOfDocument, offset: (text as NSString).range(of: placeholder, options: .backwards).location)
    }

    private var maxTextRange: UITextRange? {
        guard let maxCursorPosition = maxCursorPosition else { return nil }
        return textRange(from: maxCursorPosition, to: maxCursorPosition)
    }

    override var selectedTextRange: UITextRange? {
        get { return super.selectedTextRange }
        set {
            guard let newRange = newValue,
                let maxCursorPosition = maxCursorPosition else {
                    super.selectedTextRange = newValue
                    return
            }

            if compare(maxCursorPosition, to: newRange.start) == .orderedAscending {
                super.selectedTextRange = textRange(from: maxCursorPosition, to: maxCursorPosition)
            } else if compare(maxCursorPosition, to: newRange.end) == .orderedAscending {
                super.selectedTextRange = textRange(from: newRange.start, to: maxCursorPosition)
            } else {
                super.selectedTextRange = newValue
            }
        }
    }

}