如何将随后的文本添加到uitextfield

Question

我有一个文本字段，其占位符为letschat。现在，只要我开始在我的文本框中输入内容，我想将我的文本框显示为some @letschat。当我的文本框为空时，我的占位符必须显示。我做到了。但是，只要我开始在我的文本框中输入内容，我就想设置它。无论我与打字我想这段文字也像可见：

一些@Lletschat

我怎样才能做到这一点？

Answer 1

顺应你的类UITextfieldDelegate，然后分配textfield.delegate = self

现在，添加这个委托的方法，如果你想用户endtyping后要追加你@letschat。

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

或者如果你想在打字时间。

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" 

} 

希望这会有所帮助。

Answer 2

您可以使用UITextFieldtextFieldDidChange的action，并在每次更改textField文本时获得调用。

就像这样：

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

如果你想改变你的具体文字的颜色，你可以检查here。

Answer 3

实现文本框的委托像这个 -

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 
} 

Answer 4

简单的解决方案：

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 
    } 
} 

有了帮手扩展：

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 
    } 
} 

难，但明确的解决方案是创建你自己的UIControl -subclass与UITextField和UILabel儿童意见：

+-----------+   +-----------+ 
| textfield | -(3px)- | @letschat | 
+-----------+   +-----------+ 

使用autolayout来保持它之间的3个像素的距离。 不要忘记配置你的班级，把所有传入的动作发送到文本字段。您可以对这些控件使用不同的字体颜色，以便用户不会对改变标签价值的努力感到困惑。

Answer 5

我创建了一个UITextField子类，它使用占位符（如果设置）作为后缀。据我所见，一切都按预期工作。也许有一些调整需要适应您的需求。

随意问，如果有不清楚的地方：

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 
      } 
     } 
    } 

} 

在这里你可以看到一个预览： https://www.dropbox.com/s/etkbme37wuxbw1q/preview.mov?dl=0