问题描述
我希望我的 swift 代码使用单独和不同的动作来制作动画。那是按顺序排列的。前 2 个动画有效，但是当我添加第三个动画时，它不再起作用并导致编译错误。您可以看到评论所在的第三个动画。我只想让所有 3 个动画都能正常工作。
import UIKit
class ViewController: UIViewController {
var block1 = UIView()
var btn = UIButton()
override func viewDidLoad() {
super.viewDidLoad()
[block1,btn].forEach{
$0.translatesAutoresizingMaskIntoConstraints = false
view.addSubview($0)
}
block1.backgroundColor = .yellow
btn.backgroundColor = .red
block1.frame = CGRect(x: 0,y: 0,width: view.frame.width,height: view.frame.height * 0.1)
btn.frame = CGRect(x: 100,y: 300,width: 100,height: 100)
btn.backgroundColor = .red
btn.addTarget(self,action: #selector(diverse),for: .touchDown)
}
@objc func diverse(){
//1
UIView.animate(withDuration: 1,animations: {
self.block1.frame = CGRect(x: 100,y: 100,height: 200)
self.block1.center = self.view.center
})
//2
{ done in
if done {
UIView.animate(withDuration: 11,animations: {
self.block1.frame = CGRect(x: 100,width: 22,height: 100)
self.block1.center = self.view.center
})
}
}
//3 does not work
{ done in
if done {
UIView.animate(withDuration: 11,width: 2,height: 100)
self.block1.center = self.view.center
})
}
}
}
}
解决方法
animate(withDuration:animations:completion:) 的 documentation 显示了它的声明，它是这样的：
class func animate(withDuration duration: TimeInterval,animations: @escaping () -> Void,completion: ((Bool) -> Void)? = nil)
completion 参数标签接受一个闭包，在动画结束时调用该闭包。
UIView.animate(withDuration: 1,animations: {
self.block1.frame = CGRect(x: 100,y: 100,width: 100,height: 200)
self.block1.center = self.view.center
}) { done in /// closure here
}
然而，第二个完成闭包没有参数标签。这就是为什么
UIView.animate(withDuration: 1,height: 200)
self.block1.center = self.view.center
}) { done in /// closure here
} { done in /// second closure? Nope.
}
... 无法编译。
相反，你想做的是
- 将第二个动画放在第一个的完成处理程序中
- 将第三个动画放在第二个的完成处理程序中
/// start first animation
UIView.animate(withDuration: 1,height: 200)
self.block1.center = self.view.center
}) { done in
/// first animation finished,start second
if done {
UIView.animate(withDuration: 11,animations: {
self.block1.frame = CGRect(x: 100,width: 22,height: 100)
self.block1.center = self.view.center
}) { done in
/// second animation finished,start third
if done {
UIView.animate(withDuration: 11,animations: {
self.block1.frame = CGRect(x: 100,width: 2,height: 100)
self.block1.center = self.view.center
})
}
}
}
}