让你的 App 开启 Multitasking 之旅（二）

硬件要求： iPad Pro, iPad Air, iPad Air 2, and iPad mini 2 以及以后设备.

Picture in Picture (PiP)

Picture in Picture 能够让你的 App 在后台继续运行视频播放

PiP 适配

AVPlayerViewController 在 iOS 8 以后取代了 MediaPlay

在 iOS 9 中，播放 API 还有 AVKit, AVFounddataion, WebKit，这 3 个 Framework 都支持 PiP

首先，去项目 -> Capabilities -> 打开 Background Modes，选择 Audio, AirPlay and Picture in Picture

设置你的 AVAudioSessionCategory 为 AVAudioSessionCategoryPlayback，可以在 AppDelegate 的 didFinishLaunchingWithOptions 中设置

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    let audioSession = AVAudioSession.sharedInstance()
    do {
        try audioSession.setCategory(AVAudioSessionCategoryPlayback)
    } catch {
    }
    // Override point for customization after application launch.
    return true
}

AVKit

在播放视频的地方做一下简单的设置

@IBAction func mediaButtonTouchUpInside(sender: UIButton) {
    let playerViewController = AVPlayerViewController()
    if let fileUrl = NSBundle.mainBundle().URLForResource("video.mov", withExtension: nil) {
        playerViewController.player = AVPlayer(URL: fileUrl)
    }
    playerViewController.allowsPictureInPicturePlayback = true
    playerViewController.delegate = self
    presentViewController(playerViewController, animated: true, completion: nil)
}    

如果希望点击视频上的回到界面，继续播放视频，可以实现这个 AVPlayerViewControllerDelegate

func playerViewController(playerViewController: AVPlayerViewController, restoreUserInterfaceForPictureInPictureStopWithCompletionHandler completionHandler: (Bool) -> Void) {
    presentViewController(playerViewController, animated: false) {
        completionHandler(true)
    }
}

这样, 你就实现了整个 AVKit 的 PictureInPicture

AVFounddataion

AVFoundation 的设置稍微复杂一点，首先声明 2 个变量

var playerLayer: AVPlayerLayer?
var avPictureInPictureConctroller: AVPictureInPictureController?

对 media 做初始化

 @IBAction func mediaButtonTouchUpInside(sender: AnyObject) {
    if let fileUrl = NSBundle.mainBundle().URLForResource("video.mov", withExtension: nil) {
        playerLayer?.removeFromSuperlayer()
        let player = AVPlayer(URL: fileUrl)
        playerLayer = AVPlayerLayer(player: player)
        playerLayer?.videoGravity = AVLayerVideoGravityResizeAspect
        playerLayer?.frame = view.bounds
        avPictureInPictureConctroller = AVPictureInPictureController(playerLayer: playerLayer!)
        avPictureInPictureConctroller?.delegate = self
        player.play()
        view.layer.addSublayer(playerLayer!)
    }
}

之后，可以手动触发 PiP

 @IBAction func startPipBarButtonTouchUpInside(sender: AnyObject) {
    avPictureInPictureConctroller?.startPictureInPicture()
}

同样，实现 AVPictureInPictureControllerDelegate

func pictureInPictureControllerWillStartPictureInPicture(pictureInPictureController: AVPictureInPictureController) {
    playerLayer?.hidden = true
}

func pictureInPictureController(pictureInPictureController: AVPictureInPictureController, restoreUserInterfaceForPictureInPictureStopWithCompletionHandler completionHandler: (Bool) -> Void) {
    playerLayer?.hidden = false
    completionHandler(true)
}

WebKit

WKWebView 将会自动支持 PictureInPicture, 如果你还使用 UIWebView, 那么可以设置 allowsPictureInPictureMediaPlayback 的属性

完整的 Demo 见这里

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