Question

我正在代码中实现撤消/重做功能，但是由于某种原因，我的重做功能无法正常工作，这是我的文本视图代码：

  func textViewDidBeginEditing(_ textView: UITextView) {
    if descBox.textColor == .lightGray {
        DescriptionCell.descPlaceholder = descBox.text
            let descText = descBox.text
            undoManager?.registerUndo(withTarget: self, handler: {
            (targetSelf) in
            targetSelf.descBox.text = descText
            targetSelf.descBox.textColor = .lightGray
        })
        descBox.text = nil
        descBox.textColor = .black
    }
}

func textViewDidEndEditing(_ textView: UITextView) {
    if descBox.text.isEmpty {
        descBox.text = DescriptionCell.descPlaceholder
        descBox.textColor = .lightGray
    }
        let descText = descBox.text
        undoManager?.registerUndo(withTarget: self, handler: {
            (targetSelf) in
            targetSelf.descBox.text = descText
        })
        }

然后我将其用于ViewController工具栏：

@objc func Undo() {
 undoManager?.undo()
}

@objc func Redo() {
 undoManager?.redo()
}

然后在viewDidLoad中：

let undoKeyboard = UIBarButtonItem(image: UIImage(named: "Image-2"), style: .plain, target: self, action: #selector(Undo))
    undoKeyboard.tintColor = .lightGray
let redoKeyboard = UIBarButtonItem(image: UIImage(named: "Image-1"), style: .plain, target: self, action: #selector(Redo))
    redoKeyboard.tintColor = .green

Answer 1

这里的问题：

func textViewDidEndEditing(_ textView: UITextView) {
    if descBox.text.isEmpty {
        descBox.text = DescriptionCell.descPlaceholder
        descBox.textColor = .lightGray
    }

    let descText = descBox.text // <== Incorrect; Text has been set
    undoManager?.registerUndo(withTarget: self, handler: { (targetSelf) in
        // Here it means to reset the text (which already set in textDidEnd), thus meaningless (unless you made changes somewhere else and want to reset to the set text, which I assume is not what you want to achieve here)
        targetSelf.descBox.text = descText
    })
}

您在此处编写的内容是使用设置的文本注册撤消管理器（textViewDidEndEditing表示字段已更改，因此descBox.text已更新）。

我建议您将其更改为textViewDidBeginEditing(_:)并在此处注册撤消管理器。样本：

func textViewDidBeginEditing(_ textView: UITextView) {

    let descText = descBox.text
    undoManager?.registerUndo(withTarget: self, handler: { (targetSelf) in
        targetSelf.descBox.text = descText
        targetSelf.descBox.resignFirstResponder()
    })
}

在那里，当您按undo时，它将设置上一个文本（在进行任何更改之前）并辞退第一响应者（也称为endEditing()）

重做无法在UndoManager中快速运行

1 个答案: