ios - 标签中的图片(Swift)

Question

我有在计算器中显示历史记录的代码，但符号(+、-、×、÷)取自“案例”(照片 1)

怎样才能让历史上的符号(+、-、×、÷)按照我设置的图片显示(图2)

@IBAction func equalitySignPressed(sender: UIButton) {
    if stillTyping {
        secondOperand = currentInput
    }
    dotIsPlaced = false

        addHistory(text: operationSign + displayResultLabel.text!)

    switch operationSign {

    case "+":
        operateWithTwoOperands{$0 + $1}
    case "-":
        operateWithTwoOperands{$0 - $1}
    case "×":
        operateWithTwoOperands{$0 * $1}
    case "÷":
        operateWithTwoOperands{$0 / $1}
    default: break
    }
}

历史:

func addHistory(text: String){
    //Add text
    resultLabelText.text =  resultLabelText.text! + "" + text
}

Answer 1

您可以制作您的符号图像并使用 NSTextAttachment 构建一个 NSAttributedAtring，它用带有符号图像的相应 NSTextAttachment 替换字符串中的文本。这是一个使用一张图片的 Playground 示例，但您可以轻松地将更多图片添加到字典中，以用图片替换所有其他符号:

import PlaygroundSupport
import UIKit

class V: UIViewController {
    let label = UILabel()
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(label)
        label.textColor = .red

    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        let expression = "5 + 5"
        let plusAttachment = NSTextAttachment()
        plusAttachment.image = UIImage(named: "star.png")
        let plusString = NSAttributedString(attachment: plusAttachment)
        let substitutions: [Character: NSAttributedString] = ["+": plusString]
        let attributedExpression = NSMutableAttributedString()
        for character in expression {
            if let substitution = substitutions[character] {
                attributedExpression.append(substitution)
            } else {
                attributedExpression.append(NSAttributedString(string: String(character)))
            }
        }
        label.attributedText = attributedExpression
        label.sizeToFit()

    }
}

PlaygroundPage.current.liveView = V()