所以我一直在做一些关于UIViewPropertyAnimator的阅读,在我一直在看的例子中,他们做了类似的事情:
animator = UIViewPropertyAnimator(duration: 2.0, curve: .easeInOut, animations: {
[unowned self, redBox] in
redBox.center.x = self.view.frame.width
redBox.transform = CGAffineTransform(rotationAngle: CGFloat.pi).scaledBy(x: 0.001, y: 0.001)
})
我不明白' [无主的自我,redBox]在'一部分。谁能解释一下我们用它做什么?
我知道无主通常用于决定如何确定引用计数,并且不能将其设置为nil,因为引用将不存在而没有另一个(作为弱的替代),但我不了解这里的使用,我不理解括号部分。它在我看来是一个动画项目的数组和它位于的视图?
完整代码如下:
import UIKit
class ViewController: UIViewController {
var animator: UIViewPropertyAnimator!
override func viewDidLoad() {
super.viewDidLoad()
//redBox
let redBox = UIView(frame: CGRect(x: 10, y: 100, width: 100, height: 100))
redBox.translatesAutoresizingMaskIntoConstraints = false// lar oss redigere posisjon og sånn selv, uten at xcode setter posisjon/størrelse i stein.
redBox.backgroundColor = .red
redBox.center.y = view.center.y
view.addSubview(redBox)
animator = UIViewPropertyAnimator(duration: 2.0, curve: .easeInOut, animations: {
[unowned self, redBox] in
redBox.center.x = self.view.frame.width
redBox.transform = CGAffineTransform(rotationAngle: CGFloat.pi).scaledBy(x: 0.001, y: 0.001)
})
// slider
let slider = UISlider()
slider.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(slider)
slider.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
slider.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
slider.addTarget(self, action: #selector(sliderChanged), for: .valueChanged)
}
func sliderChanged(_ sender: UISlider){
animator.fractionComplete = CGFloat(sender.value)
}
}
答案 0 :(得分:4)
我们需要使用weak
或unowned
,否则将创建所有权(参考)周期(self
=> animator
=> { {1}} => animations
)。
我们可以使用self
代替unowned
,因为我们可以确保将weak
和self
一起销毁,并在animator
解除分配时,动画不再运行。