radars

ViewController-UICollisionBehaviorDelegate.swift

class ViewController: UIViewController {
    var animator: UIDynamicAnimator!
    var gravity: UIGravityBehavior!
    var collision: UICollisionBehavior!
  
  override func viewDidLoad() {
        super.viewDidLoad()
        
        // --------------------------------------
        //
        let customView = UIView(frame: CGRect(x: 100, y: 100, width: 100, height: 100))
        // more code....
        
        //
        animator = UIDynamicAnimator(referenceView: view)
        
        // mode code....
        
        //
        collision = UICollisionBehavior(items: [customView])
        collision.collisionDelegate = self
        // more code
        animator.addBehavior(collision)
  }
  
}

extension ViewController: UICollisionBehaviorDelegate {
    
    // This will be marked as a warning suggesting to add private property because it nearly matches one of the UICollisionBehaviorDelegate methods.
    // but it's the same deinition.
    func collisionBehavior(_ behavior: UICollisionBehavior, beganContactFor item: UIDynamicItem, withBoundaryIdentifier identifier: NSCopying?, at p: CGPoint) {
        print("Boundary contact occurred - \(String(describing: identifier))")
        
        guard let collidingView = item as? UIView else { return }
        
        collidingView.backgroundColor = UIColor.yellow
        UIView.animate(withDuration: 0.3) {
            collidingView.backgroundColor = UIColor.gray
        }
        
    }

}