如何在 swift 中突出显示文本时触发事件

Question

我想制作一个图书应用程序，用户可以在其中阅读其中的章节。我想添加一项功能，用户可以在其中突出显示文本并将其保存在应用程序中以供将来参考。在 swift 中选择文本后如何触发事件（如带有要突出显示的图标的按钮）？请帮助

我用谷歌搜索了好几个小时，但一无所获

//
//  ViewController.swift
//  platesofned
//
//  Created by Mauricio Kiyama on 5/13/19.
//  Copyright © 2019 Mauricio Kiyama. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    let myTextView: UITextField = {
        let label = UITextField()
        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = "Hello World"
        label.isSelected = true
        label.textColor = .black
        return label
    }()


    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(myTextView)
        myTextView.widthAnchor.constraint(equalToConstant: 100).isActive = true
        myTextView.heightAnchor.constraint(equalToConstant: 100).isActive = true
        myTextView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        myTextView.topAnchor.constraint(equalTo: view.topAnchor, constant: 100).isActive = true

        if let textRange = myTextView.selectedTextRange {

            let selectedText = myTextView.text(in: textRange)

            print(selectedText)
        }
    }


}

我想要一个在选择任何文本后都有按钮的框。

Answer 1

假设您询问如何在 UITextField 中的选择发生变化时获取事件，您需要将观察者添加到 UITextField 的 "selectedTextRange" 属性（来自 UITextInput协议）。

这里是一个小的示例视图控制器，用于侦听文本字段的此类事件：

class MyVC: UIViewController {
    var textField: UITextField!

    @objc override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == "selectedTextRange" {
            if let tf = object as? UITextField {
                // This is our event and text field
                if let range = tf.selectedTextRange {
                    print("Updated selection = \(range)")
                }

                return
            }
        }

        // This isn't the event or the object we care about, pass it on
        super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .yellow

        textField = UITextField(frame: CGRect(x: 0, y: 0, width: 300, height: 44))
        textField.text = "Hello there. How are you?"

        // Options is empty because we don't care about the old range and we can get the new range from the text field
        textField.addObserver(self, forKeyPath: "selectedTextRange", options: [], context: nil)

        view.addSubview(textField)
    }

    deinit {
        textField.removeObserver(self, forKeyPath: "selectedTextRange")
    }
}

如何在 swift 中突出显示文本时触发事件

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