基础知识

UIDynamic是物理仿真动画,使用前先了解三个类:
物理仿真元素（Dynamic Item）:要执行动画的元素,需要遵守UIDynamicItem协议,对于UIView我们直接使用即可,它已经遵守了.

物理仿真行为（Dynamic Behavior）:要执行的仿真行为,例如仿重力下降,仿物体碰到障碍物,目前提供的仿真行为有: UIGravityBehavior(重力行为),UICollisionBehavior(碰撞行为),UISnapBehavior(捕捉行为),UIPushBehavior(推动行为),UIAttachmentBehavior(附着行为),UIDynamicItemBehavior(动力元素行为).

物理仿真器（Dynamic Animator): UIDynamicAnimator,让仿真元素执行仿真动画.

应用

实现重力和碰撞的仿真行为动画

数字1.gif

class ViewController: UIViewController, UIDynamicAnimatorDelegate { var dynamicAnimator = UIDynamicAnimator() //物理仿真器 var imageView: UIImageView! override func viewDidLoad() { super.viewDidLoad() self.imageView = UIImageView(frame: CGRect.init(x: 50, y: 350, width: 100, height: 100)) self.imageView.backgroundColor = UIColor.red self.imageView.layer.cornerRadius = 50 self.imageView.layer.masksToBounds = true self.view.addSubview(self.imageView) }

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    dynamicAnimator = UIDynamicAnimator(referenceView: self.view)
    dynamicAnimator.delegate = self
    let itemBehavior = UIDynamicItemBehavior(items: [self.imageView])
    itemBehavior.elasticity = 0.5
    dynamicAnimator.addBehavior(itemBehavior)
    
    //创建并添加重力行为
    let gravityBehavior = UIGravityBehavior(items: [self.imageView])
    gravityBehavior.magnitude = 1
    //下降的角度
    gravityBehavior.angle = 45
    dynamicAnimator.addBehavior(gravityBehavior)
    
    //创建并添加碰撞行为
    let collisionBehavior = UICollisionBehavior(items: [self.imageView])
    collisionBehavior.translatesReferenceBoundsIntoBoundary = true
    collisionBehavior.collisionMode = .everything
    dynamicAnimator.addBehavior(collisionBehavior)
}

//监听动画结束
func dynamicAnimatorDidPause(_ animator: UIDynamicAnimator) {
    self.imageView.frame = CGRect.init(x: 50, y: 350, width: 100, height: 100)
}

}

`