Adding-scrubbing-support-to-video-playback.swift

import UIKit
import AVKit

class VideoView: UIView {
  
  // video layer that will stream the url
  private let videoLayer = AVPlayerLayer()
  
  // pan gesture used for scrubbing
  private let panGesture = UIPanGestureRecognizer()
  
  // time when scrubbing began
  private var scrubbingBeginTime: CMTime?

  // setup view
  override init(frame: CGRect) {
    super.init(frame: frame)
    // self
    backgroundColor = .black
    // setup videoPlayer
    videoLayer.videoGravity = .resizeAspect
    layer.addSublayer(videoLayer)
    // setup panGesture
    panGesture.minimumNumberOfTouches = 1
    panGesture.maximumNumberOfTouches = 1
    panGesture.cancelsTouchesInView = true
    panGesture.addTarget(self, action: #selector(didScrub(recognizer:)))
    addGestureRecognizer(panGesture)
  }
  
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  
  override func layoutSublayers(of layer: CALayer) {
    super.layoutSublayers(of: layer)
    // resize videoLayer frame to fit bounds
    videoLayer.frame = bounds
  }
  
  override func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
    if gestureRecognizer == panGesture {
      // only allow pan gesture to begin when panning horizontally
      let translation = panGesture.translation(in: self)
      return abs(translation.x) >= 0 && abs(translation.x) > abs(translation.y)
    }
    return super.gestureRecognizerShouldBegin(gestureRecognizer)
  }

  func beginStreaming() {
    // setup player for videoLayer
    let url = URL(string: "https://bitdash-a.akamaihd.net/content/MI201109210084_1/m3u8s/f08e80da-bf1d-4e3d-8899-f0f6155f6efa.m3u8")!
    let player = AVPlayer(url: url)
    videoLayer.player = player
    // begin playback
    videoLayer.player?.play()
  }
  
  @objc private func didScrub(recognizer: UIPanGestureRecognizer) {
    guard videoLayer.isReadyForDisplay == true, let player = videoLayer.player, let currentItem = player.currentItem else {
      return
    }
    switch recognizer.state {
    case .possible:
      // nothing to do here
      break
    case .began:
      // pause playback when user begins panning
      videoLayer.player?.pause()
      // set time scrubbing began
      scrubbingBeginTime = currentItem.currentTime()
    case .changed:
      guard let scrubbingBeginTime = scrubbingBeginTime else {
        return
      }
      let totalSeconds = currentItem.duration.seconds
      // translate point of pan in view
      let point = recognizer.translation(in: self)
      let scrubbingBeginPercent = Double(scrubbingBeginTime.seconds/totalSeconds)
      // calculate percentage of point in view
      var percent = Double(point.x/bounds.width)
      percent += scrubbingBeginPercent
      if percent < 0 {
        percent = 0
      } else if percent > 1.0 {
        percent = 1.0
      }
      // calculate time to seek to in video timeline
      let seconds = Float64(percent * totalSeconds)
      let time = CMTimeMakeWithSeconds(seconds, preferredTimescale: currentItem.duration.timescale)
      player.seek(to: time, toleranceBefore: CMTime.zero, toleranceAfter: CMTime.zero)
    case .ended, .cancelled, .failed:
      // reset scrubbing begin time
      scrubbingBeginTime = nil
      // resume playback after user stops panning
      videoLayer.player?.play()
    @unknown default:
      break
    }
  }
}