Dynamics Playground - PIP using field behaviors

pipDynamics.playground

import UIKit
import PlaygroundSupport

class DummyVC: UIViewController {
    
    let margin: CGFloat = 20
    
    override func viewDidLoad() {
        view.backgroundColor = .green
        view.addSubview(pipView)
        
        animator.setValue(true, forKey: "debugEnabled")
        let scale = CGAffineTransform(scaleX: 0.5, y: 0.5)
        
        for x in 0 ..< 2 {
            for y in 0 ..< 2 {
                let springField = UIFieldBehavior.springField()
                springField.position = CGPoint(x: view.bounds.maxX * (CGFloat(x) + 0.5)/2, y: view.bounds.maxY * (CGFloat(y) + 0.5)/2)
                springField.region = UIRegion(size: view.bounds.size.applying(scale))
                
                animator.addBehavior(springField)
                springField.addItem(pipView)
            }
        }
        animator.addBehavior(itemBehavior)
        pipView.addGestureRecognizer(panGesture)
    }
    
    lazy var panGesture: UIPanGestureRecognizer = {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(self.handlePan(sender:)))
        return panGesture
    }()
    
    lazy var animator:UIDynamicAnimator = {
        return UIDynamicAnimator(referenceView: view)
    }()
    
    var pipView: UIView = {
        let view = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 200))
        view.backgroundColor = .red
        return view
    }()

    lazy var itemBehavior: UIDynamicItemBehavior = {
        let itemBehavior = UIDynamicItemBehavior(items: [pipView])
        // Adjust these values to change the "stickiness" of the view
        itemBehavior.density = 0.001
        itemBehavior.resistance = 60
        itemBehavior.friction = 0.0
        itemBehavior.allowsRotation = false
        return itemBehavior
    }()
    
    lazy var attachment: UIAttachmentBehavior = {
        let attachment = UIAttachmentBehavior(item: pipView, attachedToAnchor: .zero)
        attachment.length = 0
        return attachment
    }()

    @objc func handlePan(sender: UIPanGestureRecognizer) {
        itemBehavior.action 
            let location = sender.location(in: view)
            let velocity = sender.velocity(in: view)
            switch sender.state
            {
            case .began:
                attachment.anchorPoint = location
                animator.addBehavior(attachment)
            case .changed:
                attachment.anchorPoint = location
            case .cancelled, .ended, .failed, .possible:
                itemBehavior.addLinearVelocity(velocity, for: pipView)
                animator.removeBehavior(attachment)
            }
        }
}

PlaygroundPage.current.liveView = DummyVC(nibName: nil, bundle: nil)