如何在Swift中断后恢复音频？

我按照指示 here,我已经把这个测试项目放在一起来处理音频播放的中断.具体来说,我正在使用默认iphone时钟应用程序中的警报作为中断.似乎中断处理程序被调用,但没有超过let = interruptionType行,因为“错误类型”出现了两次.

import UIKit
import AVFoundation

class ViewController: UIViewController {

    var player = AVAudioPlayer()

    let audioPath = NSBundle.mainBundle().pathForResource("rachmaninov-romance-sixhands-alianello",ofType: "mp3")!

    func handleInterruption(notification: NSNotification) {

        guard let interruptionType = notification.userInfo?[AVAudioSessionInterruptionTypeKey] as? AVAudioSessionInterruptionType else { print("wrong type"); return }

        switch interruptionType {

        case .Began:
            print("began")
            // player is paused and session is inactive. need to update UI)
            player.pause()
            print("audio paused")

        default:
            print("ended")
            /**/
            if let option = notification.userInfo?[AVAudioSessionInterruptionoptionKey] as? AVAudioSessionInterruptionoptions where option == .ShouldResume {
                // ok to resume playing,re activate session and resume playing
                // need to update UI
                player.play()
                print("audio resumed")
            }
            /**/
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view,typically from a nib.

        do {
            try player = AVAudioPlayer(contentsOfURL: NSURL(fileURLWithPath: audioPath))
            player.numberOfLoops = -1 // play indefinitely
            player.preparetoPlay()
            //player.delegate = player

        } catch {
            // process error here
        }

        // enable play in background https://stackoverflow.com/a/30280699/1827488 but this audio still gets interrupted by alerts
        do {
            try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
            print("AVAudioSession Category Playback OK")
            do {
                try AVAudioSession.sharedInstance().setActive(true)
                print("AVAudioSession is Active")
            } catch let error as NSError {
                print(error.localizedDescription)
            }
        } catch let error as NSError {
            print(error.localizedDescription)
        }

        // add observer to handle audio interruptions
        // using 'object: nil' does not have a noticeable effect
        let theSession = AVAudioSession.sharedInstance()
        NSNotificationCenter.defaultCenter().addobserver(self,selector: #selector(ViewController.handleInterruption(_:)),name: AVAudioSessionInterruptionNotification,object: theSession)

        // start playing audio
        player.play()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // dispose of any resources that can be recreated.
    }
}

此外,按照一个想法here,我已经修改了处理程序

func handleInterruption(notification: NSNotification) {

        //guard let interruptionType = notification.userInfo?[AVAudioSessionInterruptionTypeKey] as? AVAudioSessionInterruptionType else { print("wrong type"); return }

        if notification.name != AVAudioSessionInterruptionNotification
            || notification.userInfo == nil{
            return
        }

        var info = notification.userInfo!
        var intValue: UInt = 0
        (info[AVAudioSessionInterruptionTypeKey] as! NSValue).getValue(&intValue)
        if let interruptionType = AVAudioSessionInterruptionType(rawValue: intValue) {

            switch interruptionType {

            case .Began:
                print("began")
                // player is paused and session is inactive. need to update UI)
                player.pause()
                print("audio paused")

            default:
                print("ended")
                /** /
                if let option = notification.userInfo?[AVAudioSessionInterruptionoptionKey] as? AVAudioSessionInterruptionoptions where option == .ShouldResume {
                    // ok to resume playing,re activate session and resume playing
                    // need to update UI
                    player.play()
                    print("audio resumed")
                }
                / **/
                player.play()
                print("audio resumed")
            }
        }
    }

结果是所有“开始”,“音频暂停”,“结束”和“音频恢复”都显示在控制台中,但音频播放实际上并未恢复.

注意：我将player.play()移动到注释掉的where where == .ShouldResume if语句之外,因为当发生.Ended中断时if条件不为真.

do {
    try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback,withOptions: AVAudioSessionCategoryOptions.MixWithOthers)
} catch {        
}