xcode iOS Swift Animation - 将图像移动到新位置
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iOS Swift Animation - Move image to the new position
提问by ekussberg
I am trying to implement this cool feature where the logo after the app loads moves up slightly and the login view appears. The problem is that when I use this code:
我正在尝试实现这个很酷的功能，其中应用程序加载后的徽标略微向上移动并出现登录视图。问题是当我使用此代码时：
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
UIView.animateWithDuration(2, animations: {
var newCenter = self.logoImage.center
newCenter.y -= 100
self.logoImage.center = newCenter
}, completion: { finished in
println("Basket doors opened!")
})
}
The logo is moved to the origin place from the place I want it to move to. So in this example logo appears already with (y-100) and then moves to the origin X,Y.
徽标从我希望它移动到的地方移动到原点。所以在这个例子中，标志已经和 (y-100) 一起出现，然后移动到原点 X,Y。
回答by sfeuerstein
Since the view isn't actually laid out / on the screen in viewDidLoad()you shouldn't be trying to animate anything there. Instead, you should wait until the view is completely presented, which happens in viewDidAppear(animated: Bool). Also, I would recommend calculating the newCentervar outside of the animation call, then simply setting self.logoImage.center = newCenterwithin the animation call.
由于视图实际上并未在屏幕上布置/显示，因此viewDidLoad()您不应该尝试在其中设置任何动画。相反，您应该等到视图完全呈现，这发生在viewDidAppear(animated: Bool). 另外，我建议newCenter在动画调用之外计算var，然后在动画调用中简单地设置self.logoImage.center = newCenter。
