How can I resume the mp4 video after transition from the background to the active state? Xcode 10.1, Swift 4.2

Question

I am showing a video in UIView. I have added a Notification feature to play video again and again after video is stoped. But let's assume user clicks home button when user is watching the video in App. After that let's assume user opens application again.(transition from the background to the active state)

In this case, video does not play. How can I resume the mp4 video after transition from the background to the active state? I think I should use applicationWillEnterForeground method in AppDelegate.swift, right? But how? Can you write a required code for this?

ViewController.swift file:

import UIKit
import AVFoundation
import AVKit

class ViewController: UIViewController {

    @IBOutlet weak var videoViewOutlet: UIView!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.setupView()

    }

    private func setupView()
    {


        let pathClouds  = URL(fileURLWithPath: Bundle.main.path(forResource: "clouds", ofType: "mp4")!)


        let player = AVPlayer(url: pathClouds)

        let newLayer = AVPlayerLayer(player: player)
        newLayer.frame = self.videoViewOutlet.frame
        self.videoViewOutlet.layer.addSublayer(newLayer)
        newLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill


        player.play()

        //loop it
        player.actionAtItemEnd = AVPlayer.ActionAtItemEnd.none

        NotificationCenter.default.addObserver(self, selector: #selector(ViewController.videoDidPlayToEnd(notification:)),
            name: NSNotification.Name(rawValue: "AVPlayerItemDidPlayToEndTimeNotification"), object: player.currentItem)



    } 

    @objc func videoDidPlayToEnd(notification: Notification)
    {
        let player: AVPlayerItem = notification.object as! AVPlayerItem
        player.seek(to: CMTime.zero)
    }

}

Here is the AppDelegate.swift file

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
        // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
        // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
        // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
        // ??????
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    }

    func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    }


}

Answer 1

You could pause / resume it based on when the app's backgrounded / foregrounded by listening for the relevant notifications inside your ViewController. Here's an example.

import UIKit
import AVFoundation
import AVKit

class ViewController: UIViewController {

    @IBOutlet weak var videoViewOutlet: UIView!
    private var player: AVPlayer!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.setupView()
    }

    private func setupView()
    {
        let pathClouds  = URL(fileURLWithPath: Bundle.main.path(forResource: "clouds", ofType: "mp4")!)

        player = AVPlayer(url: pathClouds)

        let newLayer = AVPlayerLayer(player: player)
        newLayer.frame = self.videoViewOutlet.frame
        self.videoViewOutlet.layer.addSublayer(newLayer)
        newLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill

        player.play()

        //loop it
        player.actionAtItemEnd = .none

        NotificationCenter.default.addObserver(self, selector: #selector(ViewController.videoDidPlayToEnd(notification:)),
                                               name: NSNotification.Name(rawValue: "AVPlayerItemDidPlayToEndTimeNotification"), object: player.currentItem)

        NotificationCenter.default.addObserver(self, selector: #selector(enteredBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(enteredForeground), name: UIApplication.willEnterForegroundNotification, object: nil)
    }

    @objc func videoDidPlayToEnd(notification: Notification)
    {
        let player: AVPlayerItem = notification.object as! AVPlayerItem
        player.seek(to: .zero, completionHandler: nil)
    }

    @objc func enteredBackground() {
        player.pause()
    }

    @objc func enteredForeground() {
        player.play()
    }
}