swift仿刻apple音樂播放器 ，來點音樂

練習到function,Array,AVPlayer,AVPlayerItem,addPeriodicTimeObserver,removeTimeObserver

主要參考同學Lucas，省掉了一些卡關時間，
花最多時間的在取得音樂正在播放的秒數與音樂總秒數，
這邊卡了好幾個小時，
抓出音樂秒數之後，還要轉成 分：秒 格式，要除60之後取餘數%
說是這樣說拉…目前還不想做，還有一些細節，改天再來處理。

#94 模仿 iOS 的 Music App 製作情歌點唱機

模仿 iOS 的 Music App 製作周興哲Eric專屬播放電台(包含進階功能）

利用 AVPlayer 播放音樂音效

Observing the Playback Time

程式碼如下

import UIKit
import AVFoundation

class ViewController: UIViewController {
    
    //var player = AVPlayer()
    var player: AVPlayer!
    
    //偵測歌曲目前播放所需的宣告
    var playerItem: AVPlayerItem?
    var timeObserverToken: Any?
    
    var playIndex = 0
    var songData = [
        album(albumname: "Back In Black", albumimage: "1", singer: "ACDC", songname: "Back In Black"),
        album(albumname: "Back In Black", albumimage: "2", singer: "ACDC", songname: "Boogie Man"),
        album(albumname: "Back In Black", albumimage: "3", singer: "ACDC", songname: "Girls Got Rhythm"),
        album(albumname: "Back In Black", albumimage: "4", singer: "ACDC", songname: "Hard as a Rock"),
        album(albumname: "Back In Black", albumimage: "5", singer: "ACDC", songname: "Hells Bells"),
        album(albumname: "Back In Black", albumimage: "6", singer: "ACDC", songname: "Shoot to Thrill"),
        album(albumname: "Back In Black", albumimage: "7", singer: "ACDC", songname: "Shot Down in Flames"),
        album(albumname: "Back In Black", albumimage: "8", singer: "ACDC", songname: "Thunderstruck"),
    ]
    
    
    func playinformation(){
        songText.text = songData[playIndex].songname
        singerText.text = songData[playIndex].singer
    }
    
    func playmusic(){
        if playIndex < songData.count{
            //解決上一首變成-1會找不到陣列資料的問題
            if playIndex < 0{
               playIndex = songData.count - 1
            }
            if let songurl = Bundle.main.url(forResource:songData[playIndex].songname, withExtension: "mp4"){
                player = AVPlayer(url: songurl)
                playerItem = AVPlayerItem(url: songurl)
            }
            cover.image = UIImage(named: songData[playIndex].albumimage)
            addPeriodicTimeObserver()
            progress.value = 0
            player.play()
        }else{
            playIndex = 0
            playmusic()
        }
    }
    
    
    //添加定期時間觀察者
    func addPeriodicTimeObserver() {
        // 每半秒查看
        let timeScale = CMTimeScale(NSEC_PER_SEC)
        let time = CMTime(seconds: 0.5, preferredTimescale: timeScale)

        timeObserverToken = player.addPeriodicTimeObserver(forInterval: time,queue: .main) {[weak self] time in
            // update player transport UI
            
            let songcurrent = self!.player.currentTime().seconds
            let songcurrentInt = Int(songcurrent)
            self!.currentText.text = "\(songcurrentInt)"
            
            let duration = self!.playerItem?.asset.duration
            let songtotal = CMTimeGetSeconds(duration!)
            let songtotalInt = Int(songtotal)
            self!.totalText.text = "\(songtotalInt)"
            
            let currenttotal:Float = Float(songcurrent / songtotal)
            self!.progress.value = currenttotal

        }
    }
    
    //移除定期時間觀察者
    func removePeriodicTimeObserver() {
        if let timeObserverToken = timeObserverToken {
            player.removeTimeObserver(timeObserverToken)
            self.timeObserverToken = nil
        }
    }
    

    @IBOutlet weak var cover: UIImageView!
    @IBOutlet weak var cover_shadow: UIView!
    @IBOutlet weak var playButton: UIButton!
    @IBOutlet weak var nextButton: UIButton!
    @IBOutlet weak var preButton: UIButton!
    @IBOutlet weak var songText: UILabel!
    @IBOutlet weak var singerText: UILabel!
    @IBOutlet weak var volumeShow: UISlider!
    @IBOutlet weak var progress: UISlider!
    @IBOutlet weak var totalText: UILabel!
    @IBOutlet weak var currentText: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        cover_shadow.layer.shadowOpacity = 0.2
        cover_shadow.layer.cornerRadius = 7
        cover.clipsToBounds = true
        cover.layer.cornerRadius = 7
        
        cover.image = UIImage(named: songData[playIndex].albumimage)
        playButton.setImage(UIImage(systemName: "play.fill"), for: .normal)
        playmusic()
        player.pause()
        playinformation()
        volumeShow.value = 0.5
        
        //  播完後，繼續播下一首
        NotificationCenter.default.addObserver(forName: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil, queue: .main) { (_) in
            //  移除監聽
            self.removePeriodicTimeObserver()
            self.playIndex += 1
            self.playmusic()
        }

    }

    @IBAction func playbtn(_ sender: Any) {
        playinformation()
        if player.rate == 0 {
          playButton.setImage(UIImage(systemName: "pause.fill"), for: .normal)
          player.play()
        }else {
          playButton.setImage(UIImage(systemName: "play.fill"), for: .normal)
          player.pause()
        }
    }
    
    @IBAction func nextbtn(_ sender: Any) {
        playIndex += 1
        playmusic()
        player.play()
        playinformation()
        
    }
    
    @IBAction func prebtn(_ sender: Any) {
        playIndex -= 1
        playmusic()
        player.play()
        playinformation()
    }
    
    @IBAction func volumeBtn(_ sender: Any) {
        let volume = volumeShow.value
        player.volume = volume
    }
    
    @IBAction func progressBtn(_ sender: Any) {
        let songcurrent = progress.value

        let duration = self.playerItem?.asset.duration
        let songtotal = CMTimeGetSeconds(duration!)
        let songtotalFloat = Float(songtotal)
        
        let songhahqa = Int(songtotalFloat * songcurrent)
        let time = CMTime(value: CMTimeValue(songhahqa), timescale: 1)
        player.seek(to: time)
    }
    
    
}