Question

我是XCode（swift）的新手，我正在尝试让UIImageView随机显示三个图像中的一个，但当我在模拟器中切换到第二个viewController时，没有任何反应，XCode突出显示结束ViewDidLoad函数说线程1：断点1.1。

如果有更好或更可靠的方法让UIImageView切换图像，我肯定想知道。

我目前的代码：

import UIKit

let imageInitialIdentity = arc4random_uniform(3)

class SecondViewController: UIViewController {



    override func viewDidLoad() {
        super.viewDidLoad()



        if(imageInitialIdentity == 0){
            imageGuess.image = UIImage(named: "0ps.pngs")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
        }
        if(imageInitialIdentity == 1){
            imageGuess.image = UIImage(named: "250ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
        }
        if(imageInitialIdentity == 2){
            imageGuess.image = UIImage(named: "500ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
        }
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.

    }


    @IBOutlet weak var imageGuess: UIImageView!

    var imageIdentity = imageInitialIdentity
    var score = 0
    let imageZero = UIImage.init(named: "0ps")
    let image250 = UIImage.init(named: "250ps")
    let image500 = UIImage.init(named: "500ps")





    @IBAction func guessZero(sender: UIButton) {

        //if zero matches the picture 0, add a point
        if imageIdentity == 0{
            score++
        }
        else{
            //print incorrect, corect answer is 0
        }

            //randomizes another picture
            let rand1 = arc4random_uniform(3)
            if rand1 == 0 {
                imageGuess.image = UIImage(named: "0ps.png")
                imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
                imageIdentity = 0
            }
            else if rand1 == 1{
                imageGuess.image = UIImage(named:"250ps.png")
                imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
                imageIdentity = 1
            }
            else if rand1 == 2{
                imageGuess.image = UIImage(named:"500ps.png")
                imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
                imageIdentity = 2
            }

    }

    @IBAction func guess250(sender: UIButton) {
        // if 150 matches the picture of 250, return true
        //randomizes another picture
        //adds one to score?
        if imageIdentity == 1{
            score++
        }


        let rand2 = arc4random_uniform(3)
        if rand2 == 0 {
            imageGuess.image = UIImage(named:"0ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
            imageIdentity = 0
        }
        else if rand2 == 1{
            imageGuess.image = UIImage(named:"250ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
            imageIdentity = 1

        }
        else if rand2 == 2{
            imageGuess.image = UIImage(named:"500ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
            imageIdentity = 2
        }
    }

    @IBAction func guess500(sender: UIButton) {
        //if 500 matches the picture of 500, return true
        //randomizes another picture
        if imageIdentity == 2{
            score++
        }


        let rand3 = arc4random_uniform(3)
        if rand3 == 0 {
            imageGuess.image = UIImage(named:"0ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
            imageIdentity = 0
        }
        else if rand3 == 1{
            imageGuess.image = UIImage(named:"250ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
            imageIdentity = 1

        }
        else if rand3 == 2{
            imageGuess.image = UIImage(named:"500ps.png")
            imageGuess.frame = CGRect(x: 51, y: 47, width: 500, height: 340)
            imageIdentity = 2
        }
    }

}

Answer 1

看起来你已经设置了一个断点。通常在单击查看错误时由意外引起。如果单击蓝色箭头按钮，它将停用断点：

Answer 2

如果代码从一个ViewController运行到此SecondViewController，并且程序在viewDidLoad中断，您可能想要检查代码如何使用其先前的类完成以及它运行SecondViewController类的原因。完成检查后，您可能希望将随机方法移出viewDidLoad以找出导致崩溃的确切原因。类似的东西：

override func viewDidLoad() 
{
    super.viewDidLoad()
    randomMethod()
}
func randomMethod() // put a break point here if viewDidLoad passes
{
     if(imageInitialIdentity == 0){
     ..... your code ....
    }
}

Answer 3

要回答您的问题，＆＃34;如果有更好或更可靠的方式让UIImageView切换图像＆＃34;。

简短的回答，不，这就是它的完成方式。您应该注意的一件事是您必须在主线程上设置图像以查看更改。 viewDidLoad方法当然在主线程上运行所以不用担心。如果您决定稍后更新imageview的图片，可以使用GCD正确更新您的用户界面。

dispatch_async(dispatch_get_main_queue(), ^{
    // update your UI here
});

如果需要在imageview中快速切换两个图像，可以使用highlightImage属性。您将此属性设置为与图像属性相同（当然使用不同的图像）。然后，您需要做的就是将突出显示的属性设置为YES或NO。

UIImageView *iv = [UIImageView new];
UIImage *firstImage = [UIImage imageNamed:@"first_image.png"];
iv.image = firstImage;
iv.highlightedImage = [UIImage imageNamed:@"second_image.png"];
// Call below code whenever you want to switch the image, by setting the boolean.
dispatch_async(dispatch_get_main_queue(), ^{
    iv.highlighted = YES;
});

我建议的一件事是使用imageview框架的图像尺寸属性。

iv.frame = CGRectMake(0, 0, firstImage.size.width, firstImage.size.height);

在UIImageView中更改图像，其他XCode问题

3 个答案: