Question

我想要一个红色圆圈的图像从屏幕顶部移动到底部，就好像是一个穿过屏幕的流星。它确实会移动，但它会在没有动画的情况下以毫秒为单位移动。如何让它像带尾巴的流星一样平滑移动？

class ViewController: UIViewController {

    let meteorImage = UIImageView()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        self.meteorImage.backgroundColor = .clear
        self.meteorImage.frame = CGRect(x: 50, y: 0, width: 50, height: 50)
        self.meteorImage.isHidden = false
        self.meteorImage.image = #imageLiteral(resourceName: "success")
        view.addSubview(self.meteorImage)
    }

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

    @IBAction func buttonPressed(_ sender: UIButton) {
        let totalHeight = Int(view.frame.height)
        var currentHeight = 0

        while currentHeight < totalHeight {
            self.meteorImage.backgroundColor = .clear
            self.meteorImage.frame = CGRect(x: 50, y: currentHeight, width: 50, height: 50)
            self.meteorImage.isHidden = false
            self.meteorImage.image = #imageLiteral(resourceName: "success")
            view.addSubview(self.meteorImage)
            currentHeight += 1
        }
    }
}

Answer 1

动画必须通过动画调用完成。

这是一种动画制作的简单方法。

UIView.animate(withDuration: 0.1, animations: { 
   // Apply Changes to frame.
})

另外考虑：不是做while循环，只需设置流星帧的最终位置，并将持续时间设置为您想要的时间。

let newFrame= CGRect(x: 50, 
                     y: currentHeight, 
                     width: 50, 
                     height: 50)

UIView.animate(withDuration: 3.0, animations: { 
   // Apply Changes to frame.
   self.meteorImage.frame = newFrame
})

如果您想让动画更复杂，可以在UIView上查看关键帧动画。

动画流星在Swift 3中从上到下行进

1 个答案: