iOS使用AVPictureInPictureController实现画中画（Picture in Picture）

概述

本文中Demo下载地址。
如果你想自定义播放器实现画中画，就可以采用 AVKit 框架中的AVPictureInPictureController类。 如果你想基础的实现画中画可以参考AVPlayerViewController实现画中画 。

使用AVPictureInPictureController实现画中画步骤

1. 创建一个项目，添加Background modes；选择Target > Signing & Capabilities项，点击“+ Capability”添加Background modes，把“Audio，AirPlay，and Picture in picture”打上对勾。如下图：

   
   
   23.png

2. 配置Audio Playback Behavior，需要设置App 的AVAudioSession的Category为playback模式，示例代码如下：

   func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
       // Override point for customization after application launch.
       
       //需要设置App 的AVAudioSession的Category为playback模式
       let audioSession = AVAudioSession.sharedInstance()
       do {
           try audioSession.setCategory(.playback)
       } catch {
           print("Setting category to AVAudioSessionCategoryPlayback failed.")
       }
       return true
   }

3. 创建一个新的AVPictureInPictureController对象，向它传递一个对显示视频内容的AVPlayerLayer的引用。需要对AVPictureInPictureController对象必须强引用才能使PiP正常功能。设置AVPictureInPictureController示例代码如下：

    var playerLayer : AVPlayerLayer = AVPlayerLayer()
    var player : AVPlayer?
    var pictureInPictureController : AVPictureInPictureController?

    //设置PictureInPicture
    func setupPictureInPicture() {
        guard let videoURL = Bundle.main.url(forResource: "v1", withExtension: "MP4") else {
            return
        }
        //设置AVPlayerLayer
        playerLayer.frame = self.view.frame
        playerLayer.videoGravity = .resizeAspect
        self.view.layer.addSublayer(playerLayer)        

        //设置AVPlayer
        let asset = AVURLAsset(url: videoURL)
        let playerItem = AVPlayerItem(asset: asset)
        player = AVPlayer(playerItem: playerItem)
        if let player = player {
            playerLayer.player = player
        }
        
        // Ensure PiP is supported by current device.  isPictureInPictureSupported()判断设备是否支持画中画
        if AVPictureInPictureController.isPictureInPictureSupported() {
            // Create a new controller, passing the reference to the AVPlayerLayer.
            pictureInPictureController = AVPictureInPictureController(playerLayer: playerLayer)
            pictureInPictureController?.delegate = self //设置代理
        } else {
            print("当前设备不支持PiP")
        }
        player?.play()
    }

4. 使用AVPictureInPictureController的pictureInPictureButtonStartImage和pictureInPictureButtonStopImage，我们可以创建一个Button，然后把Button的image设置为pictureInPictureButtonStartImage或者pictureInPictureButtonStopImage。示例代码如下：

    func addPipButton() {
        //设置开启或者关闭pictureInPicture
        pipButton = UIButton(type: .system)
        //系统默认的pictureInPictureButtonStartImage
        let startImage = AVPictureInPictureController.pictureInPictureButtonStartImage
        pipButton.setImage(startImage, for: .normal)
        pipButton.frame = CGRect(x: 10, y: 20, width: 40, height: 40)
        pipButton.addTarget(self, action: #selector(clickPipButton(_:)), for: .touchUpInside)
        self.view.addSubview(pipButton)
    }

    
    @objc func clickPipButton(_ sender: Any) {
        //判断Pip是否在Active状态
        guard let isActive = pictureInPictureController?.isPictureInPictureActive else { return }
        if (isActive) {
           //停止画中画
            pictureInPictureController?.stopPictureInPicture()
            let startImage = AVPictureInPictureController.pictureInPictureButtonStartImage
            pipButton.setImage(startImage, for: .normal)
        } else {
            //启动画中画
            pictureInPictureController?.startPictureInPicture()
            //系统默认的pictureInPictureButtonStopImage
            let stopImage = AVPictureInPictureController.pictureInPictureButtonStopImage
            pipButton.setImage(stopImage, for: .normal)
        }
    }

5. 然后 build and run你的项目即可实现一个自定义的画中画Demo。
   效果图如下：

   
   
   25.PNG

AVPictureInPictureController的一些常用方法：

//开始启动画中画
open func startPictureInPicture()

//停止画中画
open func stopPictureInPicture()

//当前是否可以使用画中画
open var isPictureInPicturePossible: Bool { get }

//当前是否处于画中画状态
open var isPictureInPictureActive: Bool { get }

//当前画中画是否被挂起
open var isPictureInPictureSuspended: Bool { get }

//这可用于临时强制播放强制内容（如法律术语或广告）
@available(iOS 14.0, *)
open var requiresLinearPlayback: Bool

AVPictureInPictureControllerDelegate的代理方法

extension ViewController : AVPictureInPictureControllerDelegate {
    func pictureInPictureControllerWillStartPictureInPicture(_ pictureInPictureController: AVPictureInPictureController) {
        print("将要开始PictureInPicture的代理方法")
    }

    func pictureInPictureControllerDidStartPictureInPicture(_ pictureInPictureController: AVPictureInPictureController) {
        print("已经开始PictureInPicture的代理方法")
    }

   
    func pictureInPictureController(_ pictureInPictureController: AVPictureInPictureController, failedToStartPictureInPictureWithError error: Error) {
        print("启动PictureInPicture失败的代理方法")
    }

    
    func pictureInPictureControllerWillStopPictureInPicture(_ pictureInPictureController: AVPictureInPictureController) {
        print("将要停止PictureInPicture的代理方法")
    }

    
    func pictureInPictureControllerDidStopPictureInPicture(_ pictureInPictureController: AVPictureInPictureController) {
        print("已经停止PictureInPicture的代理方法")
    }

    
    func pictureInPictureController(_ pictureInPictureController: AVPictureInPictureController, restoreUserInterfaceForPictureInPictureStopWithCompletionHandler completionHandler: @escaping (Bool) -> Void) {
        //此方法执行在pictureInPictureControllerWillStopPictureInPicture代理方法之后，在pictureInPictureControllerDidStopPictureInPicture执行之前。 但是点击“X”移除画中画时，不执行此方法。
        print("PictureInPicture停止之前恢复用户界面")
    }
}