Interactive Animation

Animation.swift

//
//  MusicListViewController.swift
//  MusicPlayer
//
//  Created by Sathish on 17/11/19.
//  Copyright © 2019 Full. All rights reserved.
//

import UIKit
import UIKit.UIGestureRecognizerSubclass

class MusicListViewController: UIViewController {
    
    @IBOutlet weak var aniView: UIView! // PanView
    @IBOutlet weak var bottomCons: NSLayoutConstraint!
//     @IBOutlet weak var heightCons: NSLayoutConstraint!
    
    @IBOutlet weak var panInView: UIView! // Pan Inside View

//     @IBOutlet weak var panInTopCons: NSLayoutConstraint!
    
    var animator: UIViewPropertyAnimator?
    var transitionAnimator: [UIViewPropertyAnimator] = []
    
    var animationProcess: [CGFloat] = []
    
    var currentState: State = .closed
    
    override func viewDidLoad() {
        super.viewDidLoad()
        configPanGesture()
    }
    
    @IBAction func didTappedButton(_ sender: Any) {
        let animator = UIViewPropertyAnimator(duration: 0.28, curve: .easeInOut) {
            self.aniView.transform = CGAffineTransform(translationX: 260, y: 0)
        }
        animator.startAnimation()
    }
    
    func configPanGesture() {
        let gesture = InstantPanGestureRecognizer(target: self, action: #selector(handlePan(recognizer:)))
        aniView.addGestureRecognizer(gesture)
    }

    @objc
    func handlePan(recognizer: UIPanGestureRecognizer) {
        
        switch recognizer.state {
            case .began:
                animateIfNeeded(state: currentState.invert)
                print("********* BEGAN STATE STARTED *********")
                transitionAnimator.forEach { $0.pauseAnimation() }
                animationProcess = transitionAnimator.map { $0.fractionComplete }
            
            case .changed:
                
                var yPoint = -(recognizer.translation(in: aniView).y / 440)
                if currentState == .open {
                    yPoint *= -1
                }
                
                if transitionAnimator[0].isReversed { yPoint *= -1 }

                print("********* CHANGED STATE STARTED *********")
                for (index, animator) in transitionAnimator.enumerated() {
                    print("Animation Process => \(animationProcess[index]) //// Translation => \(yPoint)")
                    animator.fractionComplete = yPoint + animationProcess[index]
            }
            
            case .ended:
                
                let yVelocity = recognizer.velocity(in: aniView).y
                let shouldClose = yVelocity > 0
                
                print("********* ENDED STATE STARTED *********")
                
                if yVelocity == 0 {
                    transitionAnimator.forEach { $0.continueAnimation(withTimingParameters: nil, durationFactor: 0) }
                    break
                }
                switch currentState {
                    case .open:
                        if !shouldClose && !transitionAnimator[0].isReversed { transitionAnimator.forEach { $0.isReversed = !$0.isReversed } }
                        if shouldClose && transitionAnimator[0].isReversed { transitionAnimator.forEach { $0.isReversed = !$0.isReversed } }
                    case .closed:
                        if shouldClose && !transitionAnimator[0].isReversed { transitionAnimator.forEach { $0.isReversed = !$0.isReversed } }
                        if !shouldClose && transitionAnimator[0].isReversed { transitionAnimator.forEach { $0.isReversed = !$0.isReversed } }
                }
                
                transitionAnimator.forEach { $0.continueAnimation(withTimingParameters: nil, durationFactor: 0) }
            
            default:
                break
        }
    }
    
    func animateIfNeeded(state: State) {
        
      guard transitionAnimator.isEmpty else { return }
        
        let panInsideAnimator = UIViewPropertyAnimator(duration: 1, dampingRatio: 2) {
            switch state {
                case .open:
                    self.panInView.transform = CGAffineTransform(translationX: 0, y: -30)
                case .closed:
                    self.panInView.transform = CGAffineTransform(translationX: 0, y: 30)
            }
        }

        let transitionAnimator = UIViewPropertyAnimator(duration: 1, dampingRatio: 1)

        transitionAnimator.addAnimations {
            switch state {
                case .open:
                    self.bottomCons.constant = 0
                case .closed:
                    self.bottomCons.constant = -300
            }
            self.view.layoutIfNeeded()
        }

        transitionAnimator.addCompletion { position in
            switch position {
                case .start:
                    self.currentState = state.invert
                case .end:
                    self.currentState = state
                case .current: break
                @unknown default: ()
            }
            switch self.currentState {
                case .open:
                    self.bottomCons.constant = 0
                case .closed:
                    self.bottomCons.constant = -300
            }
            print("Animation Removing...")
            self.transitionAnimator.removeAll()
        }
                        
        transitionAnimator.startAnimation()
        panInsideAnimator.startAnimation()

        self.transitionAnimator.append(transitionAnimator)
        self.transitionAnimator.append(panInsideAnimator)
    }
}



class InstantPanGestureRecognizer: UIPanGestureRecognizer {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        if (self.state == UIGestureRecognizer.State.began) { return }
        super.touchesBegan(touches, with: event)
        self.state = UIGestureRecognizer.State.began
    }
}


public enum State {
    case open
    case closed
    
    var invert: State {
        switch self {
            case .open: return .closed
            case .closed: return .open
        }
    }
}