如何在从后台转换到活动状态后恢复mp4视频？代码10.1，Swift 4.2

我正在

UIView

中播放视频。我添加了一个通知功能，可以在视频停止后反复播放视频。但假设用户在应用程序中观看视频时单击了home按钮。在此之后，假设用户再次打开应用程序。（从后台转换到活动状态）

在这种情况下，不播放视频。如何在从后台转换到活动状态后恢复mp4视频？我想我应该在AppDelegate.swift中使用

applicationWillEnterForeground

方法，对吗？但是怎么做呢？你能为此编写一个必需的代码吗

ViewController.swift文件：

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)
    }

}

这是AppDelegate.swift文件

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:.
    }


}

---

通过监听ViewController中的相关通知，您可以根据应用的背景/前景暂停/恢复它。这里有一个例子

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()
    }
}

---

通过监听ViewController中的相关通知，您可以根据应用的背景/前景暂停/恢复它。这里有一个例子

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()
    }
}