用swift语言写一个富文本编辑器的用户界面

好的，下面是一个使用Swift语言编写的富文本编辑器用户界面的示例：

import UIKit

class RichTextEditorViewController: UIViewController, UITextViewDelegate {

    var textView: UITextView!
    var toolbar: UIToolbar!

    override func viewDidLoad() {
        super.viewDidLoad()

        // 设置文本视图
        textView = UITextView(frame: view.bounds)
        textView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        textView.delegate = self
        view.addSubview(textView)

        // 设置工具栏
        toolbar = UIToolbar(frame: CGRect(x: 0, y: view.bounds.height - 44, width: view.bounds.width, height: 44))
        toolbar.autoresizingMask = [.flexibleWidth, .flexibleTopMargin]
        view.addSubview(toolbar)

        // 添加工具栏按钮
        let boldButton = UIBarButtonItem(title: "B", style: .plain, target: self, action: #selector(boldButtonTapped))
        let italicButton = UIBarButtonItem(title: "I", style: .plain, target: self, action: #selector(italicButtonTapped))
        let underlineButton = UIBarButtonItem(title: "U", style: .plain, target: self, action: #selector(underlineButtonTapped))
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        toolbar.items = [boldButton, italicButton, underlineButton, flexibleSpace]

        // 设置文本视图的样式
        let font = UIFont.systemFont(ofSize: 16)
        let attributes: [NSAttributedString.Key: Any] = [NSAttributedString.Key.font: font]
        textView.typingAttributes = attributes
    }

    // 处理工具栏按钮的点击事件
    @objc func boldButtonTapped() {
        let range = textView.selectedRange
        let existingAttributes = textView.textStorage.attributes(at: range.location, effectiveRange: nil)
        var newAttributes = existingAttributes
        newAttributes[NSAttributedString.Key.font] = UIFont.boldSystemFont(ofSize: 16)
        textView.textStorage.addAttributes(newAttributes, range: range)
    }

    @objc func italicButtonTapped() {
        let range = textView.selectedRange
        let existingAttributes = textView.textStorage.attributes(at: range.location, effectiveRange: nil)
        var newAttributes = existingAttributes
        newAttributes[NSAttributedString.Key.font] = UIFont.italicSystemFont(ofSize: 16)
        textView.textStorage.addAttributes(newAttributes, range: range)
    }

    @objc func underlineButtonTapped() {
        let range = textView.selectedRange
        let existingAttributes = textView.textStorage.attributes(at: range.location, effectiveRange: nil)
        var newAttributes = existingAttributes
        newAttributes[NSAttributedString.Key.underlineStyle] = NSUnderlineStyle.single.rawValue
        textView.textStorage.addAttributes(newAttributes, range: range)
    }

    // UITextViewDelegate方法
    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        // 处理删除样式
        if text == "" {
            let existingAttributes = textView.textStorage.attributes(at: range.location, effectiveRange: nil)
            var newAttributes = existingAttributes
            newAttributes[NSAttributedString.Key.font] = UIFont.systemFont(ofSize: 16)
            newAttributes[NSAttributedString.Key.underlineStyle] = NSUnderlineStyle.none.rawValue
            textView.textStorage.addAttributes(newAttributes, range: range)
        }
        return true
    }

}

这个示例代码包括一个文本视图和一个工具