ios - 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，用户将在其中阅读其中的章节。我想添加一项功能，用户可以突出显示文本并将其保留在应用程序中以供将来引用。在 swift 中选择文本后如何触发事件(例如带有突出显示图标的按钮)？请帮忙

我在谷歌上搜索了几个小时，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有按钮的框。

Answer 1

假设您询问如何在 UITextField 中的选择更改时获取事件，则需要向 UITextField 的“selectedTextRange”属性添加一个观察者(来自 UITextInput 协议(protocol))。

这是一个小的 View Controller 示例，用于监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")
    }
}