iOSアプリにLottieのアニメーションを追加する方法（Swift）

import Lottie

// 1. Create the LottieAnimationView
private var animationView: LottieAnimationView?

override func viewDidLoad() {

  super.viewDidLoad()
  
  // 2. Start LottieAnimationView with animation name (without extension)
  
  animationView = .init(name: "coffee")
  
  animationView!.frame = view.bounds
  
  // 3. Set animation content mode
  
  animationView!.contentMode = .scaleAspectFit
  
  // 4. Set animation loop mode
  
  animationView!.loopMode = .loop
  
  // 5. Adjust animation speed
  
  animationView!.animationSpeed = 0.5
  
  view.addSubview(animationView!)
  
  // 6. Play animation
  
  animationView!.play()
  
}

override func viewDidLoad() {

  super.viewDidLoad()
  
  // 1. Set animation content mode
  
  animationView.contentMode = .scaleAspectFit
  
  // 2. Set animation loop mode
  
  animationView.loopMode = .loop
  
  // 3. Adjust animation speed
  
  animationView.animationSpeed = 0.5
  
  // 4. Play animation
  animationView.play()
}

enum ProgressKeyFrames: CGFloat {

  case start = 140
  
  case end = 187
  
  case complete = 240
  
}

private var progressView: LottieAnimationView?

override func viewDidLoad() {

  super.viewDidLoad()
  // make sure the name of the animation matches the imported file
  
  progressView = .init(name: "download")
  
  progressView!.frame = view.bounds
  
  progressView!.contentMode = .scaleAspectFit
  
  view.addSubview(progressView!)
  
}

// start the download

private func startProgress() {

  // play from frame 0 to the start download of progress
  
  progressView?.play(fromFrame: 0, toFrame: ProgressKeyFrames.start.rawValue, loopMode: .none) { [weak self] (_) in
  
    self?.startDownload()
	
  }
  
}

// progress from 0 to 100%

private func startDownload() {

  // play animation from start to end of download progress
  
  progressView?.play(fromFrame: ProgressKeyFrames.start.rawValue, toFrame: ProgressKeyFrames.end.rawValue, loopMode: .none) { [weak self] (_) in
  
    self?.endDownload()
	
  }
  
}

// download is completed, we show the completion state

private func endDownload() {

  // download is completed, we show the completion state
  
  progressView?.play(fromFrame: ProgressKeyFrames.end.rawValue, toFrame: ProgressKeyFrames.complete.rawValue, loopMode: .none)
  
}

override func viewDidAppear(_ animated: Bool) {

  super.viewDidAppear(animated)
  
  startProgress()
  
}

// start download

private func startDownload() {

  // 1. URL to download from
  
  let url = URL(string: "https://archive.org/download/SampleVideo1280x7205mb/SampleVideo_1280x720_5mb.mp4")!
  
  // 2. Setup download task and start download
  
  let configuration = URLSessionConfiguration.default
  
  let operationQueue = OperationQueue()
  
  let session = URLSession(configuration: configuration, delegate: self, delegateQueue: operationQueue)
  
  let downloadTask = session.downloadTask(with: url)
  
  downloadTask.resume()
  
}

// MARK: - Download Delegate

extension ViewController: URLSessionDownloadDelegate {
  // handles download progress
  
  func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
  
    let percentDownloaded: CGFloat = CGFloat(totalBytesWritten) / CGFloat(totalBytesExpectedToWrite)
	
    DispatchQueue.main.async {
	
      self.progress(to: percentDownloaded)
	  
    }
	
  }
  

  // finishes download
  
  func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
  
    DispatchQueue.main.async {
	
      self.endDownload()
	  
    }
	
  }
  
}

// sets download progress

private func progress(to progress: CGFloat) {

  // 1. We get the range of frames specific for the progress from 0-100%
  
  let progressRange = ProgressKeyFrames.end.rawValue - ProgressKeyFrames.start.rawValue
  
  // 2. Then, we get the exact frame for the current progress
  
  let progressFrame = progressRange * progress
  
  // 3. Then we add the start frame to the progress frame
  // Considering the example that we start in 140, and we moved 30 frames in the progress, we should show frame 170 (140+30)
  
  let currentFrame = progressFrame + ProgressKeyFrames.start.rawValue
  
  // 4. Manually setting the current animation frame
  
  progressView?.currentFrame = currentFrame
  
  print("Downloading \((progress*100).rounded())%")
  
}