如何在iOS中向上移动充满活力的文本

Question

我想制作一个应用程序，在视图的中心打招呼，等待几秒钟，然后动画化到顶部（有点像你在许多应用程序中看到的登录视图）

无论我尝试什么，我都无法将文本保持在x轴的中心。你能查一下我的代码并告诉我错误在哪里吗？

谢谢

    // Blur Effect
    var blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Light)
    var blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.frame = view.bounds
    view.addSubview(blurEffectView)
    // Vibrancy Effect
    var vibrancyEffect = UIVibrancyEffect(forBlurEffect: blurEffect)
    var vibrancyEffectView = UIVisualEffectView(effect: vibrancyEffect)
    vibrancyEffectView.frame = view.bounds
    // Add label to the vibrancy view
    vibrancyEffectView.contentView.addSubview(vibrantLabel)
    vibrantLabel.textAlignment = NSTextAlignment.Center

    // Add the vibrancy view to the blur view
    blurEffectView.contentView.addSubview(vibrancyEffectView)

    UIView.animateWithDuration(1, delay: 1, options: .CurveEaseIn, animations: {() -> Void in
        self.vibrantLabel.frame = CGRectMake(0, 100, self.vibrantLabel.frame.width, self.vibrantLabel.frame.height)
        }, completion: {(finished: Bool) -> Void in
            self.view.alpha = 1
    })

Answer 1

要解决您的问题，只需在动画过程中保留标签的x原点即可。请尝试这条线路：

self.vibrantLabel.frame = CGRectMake(self.vibrantLabel.frame.origin.x, 100, self.vibrantLabel.frame.width, self.vibrantLabel.frame.height)

您将x轴上的原点设置为零，因此标签的动画与其父视图左对齐。

Answer 2

找到了解决方案。我需要在viewDidLayoutSubviews（）中设置初始位置，然后在viewDidAppear（）中设置动画

@IBOutlet var vibrantLabel: UILabel!
override func viewDidLoad() {
    super.viewDidLoad()
    // Blur Effect
    var blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Light)
    var blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.frame = view.bounds
    view.addSubview(blurEffectView)
    // self.vibrantLabel.layer.anchorPoint = (CGPointMake(-0.25, -2.65))
    // Vibrancy Effect
    var vibrancyEffect = UIVibrancyEffect(forBlurEffect: blurEffect)
    var vibrancyEffectView = UIVisualEffectView(effect: vibrancyEffect)
    vibrancyEffectView.frame = view.bounds
    // Add label to the vibrancy view
    view.addSubview(vibrantLabel)
    vibrantLabel.textAlignment = NSTextAlignment.Center
    // Add the vibrancy view to the blur view
    blurEffectView.contentView.addSubview(vibrancyEffectView)
}
override func viewDidLayoutSubviews() {

    vibrantLabel.center = CGPointMake(view.frame.midX, view.frame.midY)
}
override func viewDidAppear(animated: Bool) {
    UILabel.animateWithDuration(1.25, delay: 1, options: .CurveEaseInOut, animations: {
        self.vibrantLabel.center = CGPointMake(self.view.frame.midX, 100)
        }) { (Bool) in
            print("success")
    }

}