UIButton颜色未恢复为原始颜色

Question

我正在制作一个测验应用程序。如果根据正确或错误的答案单击，其按钮颜色会发生变化。但我想在延迟一段时间后将颜色恢复到原来的颜色。延迟0.2秒后颜色改变但没有恢复默认。

这是我的代码：

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var questionLabel: UILabel!
    @IBOutlet weak var progressBar: UIProgressView!
    @IBOutlet weak var falseButton: UIStackView!
    @IBOutlet weak var trueButton: UIStackView!

    var QuestionNumber=0
    var score=0
    var questionArray = [
        Question(q: "A slug's blood is green.", a: "True"),
        Question(q: "Approximately one quarter of human bones are in the feet.", a: "True"),
        Question(q: "The total surface area of two human lungs is approximately 70 square metres.", a: "True"),
        Question(q: "In West Virginia, USA, if you accidentally hit an animal with your car, you are free to take it home to eat.", a: "True"),
        Question(q: "In London, UK, if you happen to die in the House of Parliament, you are technically entitled to a state funeral, because the building is considered too sacred a place.", a: "False"),
        Question(q: "It is illegal to pee in the Ocean in Portugal.", a: "True"),
        Question(q: "You can lead a cow down stairs but not up stairs.", a: "False"),
        Question(q: "Google was originally called 'Backrub'.", a: "True"),
        Question(q: "Buzz Aldrin's mother's maiden name was 'Moon'.", a: "True"),
        Question(q: "The loudest sound produced by any animal is 188 decibels. That animal is the African Elephant.", a: "False"),
        Question(q: "No piece of square dry paper can be folded in half more than 7 times.", a: "False"),
        Question(q: "Chocolate affects a dog's heart and nervous system; a few ounces are enough to kill a small dog.", a: "True")
    ]

    override func viewDidLoad() {
        super.viewDidLoad()
        //fill the current question on screem
        updateUI()
    }
    
    @IBAction func answerButtonPressed(_ sender: UIButton) {
        // checking question not going to out of bound
        if QuestionNumber + 1 < questionArray.count
        {
            let userAnswer = sender.currentTitle
            
            let actualAnswer = questionArray[QuestionNumber].answer
           
            if userAnswer == actualAnswer
            {   // change the backgroundcolor
                sender.backgroundColor=UIColor.green
                score+=1
            }
            else
            {   sender.backgroundColor=UIColor.red
                score-=1
            }
            QuestionNumber+=1
            // let some delay  0.2sec 
            Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: #selector(updateUI), userInfo: nil, repeats: false)
           
        }
       else
        {
           questionLabel.text="Done. Your score is \(score)"
           print(score)
          
       }
    }

    @objc func updateUI()
    {
        questionLabel.text=questionArray[QuestionNumber].text
        trueButton.backgroundColor=UIColor.clear
        falseButton.backgroundColor=UIColor.clear
        
        print("color changed")
    }
}

Answer 1

针对您的情况，一个非常简单的解决方案是使用 GCD 而不是 Timer： 只需更换这个：

Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: #selector(updateUI), userInfo: nil, repeats: false)

这样：

DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
    self.questionLabel.text = self.questionArray[QuestionNumber].text
    sender = UIColor.clear
    print("color changed")
}

在没有GCD的情况下解决问题是：

1. 转到您的 Storyboard 或 Xib
2. 重新附加 UIButtons 而不是 UIStackViews。现在您将 UIStackViews 附加到视图控制器而不是 UIButtons。

希望有帮助。