在 UITextView Swift 3 中创建编号列表

Question

我正在尝试从用户输入到 UITextView 的信息中创建一个编号列表。例如，

1. 列出第一项
2. 列出第二项
3. 列出第三项

这是我尝试过但没有给我想要的效果的代码。 var currentLine: Int = 1

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
    // Add "1" when the user starts typing into the text field
    if  (textView.text.isEmpty && !text.isEmpty) {
        textView.text = "\(currentLine). "
        currentLine += 1
    }
    else {
        if text.isEmpty {
            if textView.text.characters.count >= 4 {
                let str = textView.text.substring(from:textView.text.index(textView.text.endIndex, offsetBy: -4))
                if str.hasPrefix("\n") {
                    textView.text = String(textView.text.characters.dropLast(3))
                    currentLine -= 1
                }
            }
            else if text.isEmpty && textView.text.characters.count == 3 {
                textView.text = String(textView.text.characters.dropLast(3))
                currentLine = 1
            }
        }
        else {
            let str = textView.text.substring(from:textView.text.index(textView.text.endIndex, offsetBy: -1))
            if str == "\n" {
                textView.text = "\(textView.text!)\(currentLine). "
                currentLine += 1
            }
        }

    }
    return true
}

这里建议：How to make auto numbering on UITextview when press return key in swift 但没有成功。

非常感谢任何帮助。

Answer 1

您可以继承 UITextView，覆盖方法 willMove(toSuperview 并使用选择器为 UITextViewTextDidChange 添加一个观察者，该选择器将您的文本分解为相应地枚举和编号的行。试试这样：

class NumberedTextView: UITextView {
    override func willMove(toSuperview newSuperview: UIView?) {
        frame = newSuperview?.frame.insetBy(dx: 50, dy: 80) ?? frame
        backgroundColor = .lightGray
        NotificationCenter.default.addObserver(self, selector: #selector(textViewDidChange), name: .UITextViewTextDidChange, object: nil)
    }
    func textViewDidChange(notification: Notification) {
        var lines: [String] = []
        for (index, line) in text.components(separatedBy: .newlines).enumerated() {
            if !line.hasPrefix("\(index.advanced(by: 1))") &&
                !line.trimmingCharacters(in: .whitespaces).isEmpty {
                lines.append("\(index.advanced(by: 1)). " + line)
            } else {
                lines.append(line)
            }
        }
        text = lines.joined(separator: "\n")
        // this prevents two empty lines at the bottom
        if text.hasSuffix("\n\n") {   
            text = String(text.characters.dropLast())
        }
    }
}

---

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let textView = NumberedTextView()
        view.addSubview(textView)
    }
}