Question

我正在尝试将 NSAttributedString 样式应用于 UITextField ，然后处理新的文本条目，按键击键。问题是，每当我替换文本时，光标将在每次更改时跳到最后。这是我目前的做法......

立即接收并显示文本更改（当我返回false 并手动执行文本替换时，同样的问题适用）

func textField(textField: UITextField!, shouldChangeCharactersInRange range: NSRange, replacementString string: String!) -> Bool {        
    let range:NSRange = NSRange(location: range.location, length: range.length)
    let newString = (textField.text as NSString).stringByReplacingCharactersInRange(range, withString: string);
    return true
}

我订阅了UITextFieldTextDidChangeNotification通知。这会触发样式。更改文本后，我使用格式化（）函数将格式化版本（ NSAttributedString ）替换为 NSString 。

func textFieldTextDidChangeNotification(userInfo:NSDictionary) {
    var attributedString:NSMutableAttributedString = NSMutableAttributedString(string: fullString)
    attributedString = format(textField.text) as NSMutableAttributedString
    textField.attributedText = attributedString
}

样式工作正常。但是，在每次文本替换后，光标会跳转到字符串的末尾。如何关闭此行为或手动将光标移回到开始编辑的位置？ ...或者在编辑时是否有更好的方法来设置文本样式？

Answer 1

使这项工作的方法是获取光标的位置，更新字段内容，然后将光标替换为其原始位置。我不确定Swift中的确切等价物，但以下是我在Obj-C中的操作方法。

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    UITextPosition *beginning = textField.beginningOfDocument;
    UITextPosition *cursorLocation = [textField positionFromPosition:beginning offset:(range.location + string.length)];

    textField.text = [textField.text stringByReplacingCharactersInRange:range withString:string];

    /* MAKE YOUR CHANGES TO THE FIELD CONTENTS AS NEEDED HERE */

    // cursorLocation will be (null) if you're inputting text at the end of the string
    // if already at the end, no need to change location as it will default to end anyway
    if(cursorLocation)
    {
        // set start/end location to same spot so that nothing is highlighted
        [textField setSelectedTextRange:[textField textRangeFromPosition:cursorLocation toPosition:cursorLocation]];
    }

    return NO;
}

Answer 2

这是一个老问题，但我遇到了类似的问题并使用以下Swift解决了这个问题：

// store the current cursor position as a range
var preAttributedRange: NSRange = textField.selectedRange 
// apply attributed string
var attributedString:NSMutableAttributedString = NSMutableAttributedString(string: fullString)
attributedString = format(textField.text) as NSMutableAttributedString
textField.attributedText = attributedString
// reapply the range
textField.selectedRange = preAttributedRange

它适用于我的应用程序环境，希望它对某人有用！

Answer 3

通过Objective-C中的代码感谢@ Stonz2。它就像一个魅力！我在Swift项目中使用它。 Swift中的相同代码：

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

    let positionOriginal = textField.beginningOfDocument
    let cursorLocation = textField.positionFromPosition(positionOriginal, offset: (range.location + NSString(string: string).length))

    /* MAKE YOUR CHANGES TO THE FIELD CONTENTS AS NEEDED HERE */

    if(cursorLocation != nil) {
        textField.selectedTextRange = textField.textRangeFromPosition(cursorLocation!, toPosition: cursorLocation!)
    }
    return false 
}

Answer 4

这是一个适用于swift 2的代码。尽情享受吧！

 func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let beginnig: UITextPosition =  textField.beginningOfDocument

    if let txt = textField.text {
        textField.text = NSString(string: txt).stringByReplacingCharactersInRange(range, withString: string)
    }

    if let cursorLocation: UITextPosition = textField.positionFromPosition(beginnig, offset: (range.location + string.characters.count) ) {
        textField.selectedTextRange = textField.textRangeFromPosition(cursorLocation, toPosition: cursorLocation)
    }

    return false
}

请注意，最后＆＃34;如果让＆＃34;应始终留在代码的末尾。

Answer 5

为补充该线程中的其他正确答案，以下是 Swift 4.2 以及 UITextField 和 UITextView

UITextField

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // Update Cursor
    let positionOriginal = textField.beginningOfDocument
    let cursorLocation = textField.position(from: positionOriginal, offset: (range.location + string.count))
    if let cursorLocation = cursorLocation {
        textField.selectedTextRange = textField.textRange(from: cursorLocation, to: cursorLocation)
    }
    return false
}

UITextView

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
    // Update Cursor
    let positionOriginal = textView.beginningOfDocument
    let cursorLocation = textView.position(from: positionOriginal, offset: (range.location + text.count))
    if let cursorLocation = cursorLocation {
        textView.selectedTextRange = textView.textRange(from: cursorLocation, to: cursorLocation)
    }
    return false
}

Answer 6

要在此处回答另一个问题：https://stackoverflow.com/a/51814368/431271，您不应该修改shouldChangeCharactersInRange中的文本，因为该委托方法仅用于让字段知道是否允许更改且不应更改。

相反，我喜欢通过订阅值更改来处理文本更改，如下所示：

textField.addTarget(self, action: #selector(handleTextChanged), for: .editingChanged)

// elsewhere in the file
func handleTextChanged(_ textField: UITextField) {
    textField.sanitizeText(map: formatText)
}

sanitizeText的实现如下：

extension UITextField {

    // Use this to filter out or change the text value without 
    // losing the current selection
    func sanitizeText(map: ((String) -> String)) {
        guard let text = self.text,
            let selection = selectedTextRange else {
                return
        }

        let newText = map(text)

        // only execute below if text is different
        guard newText != text else { return }

        // determine where new cursor position should start
        // so the cursor doesnt get sent to the end
        let diff = text.count - newText.count
        let cursorPosition = offset(from: beginningOfDocument, to: selection.start) - diff

        self.text = newText

        // notify the value changed (to ensure delegate methods get triggered)
        sendActions(for: .valueChanged)

        // update selection afterwards
        if let newPosition = position(from: beginningOfDocument, offset: cursorPosition) {
            selectedTextRange = textRange(from: newPosition, to: newPosition)
        }
    }
}

格式化UITextField文本而不将光标移动到最后

6 个答案: