如何在“下一步”按钮上播放下一首歌曲

Question

我正在使用AVAudioPlayer()创建音乐播放器，因此我有多个JSON格式的音频文件url，因此我已全部显示在表格视图中，然后在didSelect上我正在播放选定的歌曲，但是我要在按钮上播放下一首歌曲，请点击此处，这是我在didSelect上播放歌曲的代码

已选择代码

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let urlstring = songs[indexPath.row]
        let strnew = urlstring.replacingOccurrences(of: "\"", with: "")
        downloadFileFromURL(url: strnew)
}

这是我从URL下载音频的功能

func downloadFileFromURL(url: String)  {

    if let audioUrl = URL(string: url) {

        let documentsDirectoryURL =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

        let destinationUrl = documentsDirectoryURL.appendingPathComponent(audioUrl.lastPathComponent)
        print(destinationUrl)

        if FileManager.default.fileExists(atPath: destinationUrl.path) {
            print("The file already exists at path")
            self.play(url: destinationUrl)
        } else {
            URLSession.shared.downloadTask(with: audioUrl, completionHandler: { (location, response, error) -> Void in
                guard let location = location, error == nil else { return }
                do {
                    try FileManager.default.moveItem(at: location, to: destinationUrl)

                    self.play(url: destinationUrl)
                    print("File moved to documents folder")
                } catch let error as NSError {
                    print(error.localizedDescription)
                }
            }).resume()
        }
    }
}

使用以下代码，我正在播放音频

func play(url: URL) {

    print("playing \(url)")

    do {

        audioPlayer = try AVAudioPlayer(contentsOf: url)
        audioPlayer.prepareToPlay()
        audioPlayer.volume = 1.0
        audioPlayer.play()

    } catch let error as NSError {

        print("playing error: \(error.localizedDescription)")

    } catch {

        print("AVAudioPlayer init failed")
    }
}

但是我无法理解如何在单击“下一步”按钮时播放下一首歌曲。我正在共享下面的User Interface的屏幕截图

在didSelect上，我可以播放所选的歌曲，但是如何管理下一首歌曲，我不确定是否可以帮助我。

Answer 1

在ViewController中只需维护一个索引值。

赞：

var currentIndex = 0

在didSelect方法中，使用indexPath行值更新当前索引值

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
   currentIndex = indexPath.row
   loadUrl()
}

使用另一种方法获取URL并播放歌曲。将

func loadUrl(){
    let urlstring = songs[currentIndex]
    let strnew = urlstring.replacingOccurrences(of: "\"", with: "")
    downloadFileFromURL(url: strnew)
}

对于上一个/下一个按钮，操作将是

@IBAction func nextBtnAction(_ sender: UIButton){
    if currentIndex + 1 < songs.count {
          currentIndex = currentIndex + 1
          loadUrl()
     }
}

@IBAction func previousBtnAction(_ sender: UIButton){
    if currentIndex != 0 {
          currentIndex = currentIndex - 1
          loadUrl()
     }
}

希望您能理解

Answer 2

添加到您的ViewController

var currentPlayingIndex: Int?

.....
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath){

    self.currentPlayingIndex = indexPath.row
    self.loadSongFromURL()
}
.....

//Button Action..
@IBAction func nextButtonAction(_ sender: Any){

    self.playSong(isForward: true)
}

@IBAction func previousButtonAction(_ sender: Any) {

    self.playSong(isForward: false)
}

private func playSong(isForward: Bool) {

    if currentPalyingIndex == nil { //Means not any song is playing
        currentPalyingIndex = 0
        self.loadSongFromURL()
    }
    else{

        if isForward {

            if self.currentPalyingIndex! < self.items.count-1 {
                self.currentPalyingIndex = self.currentPalyingIndex! + 1
                self.loadSongFromURL()
            }
            else {
                // handle situation while reach at last
            }
        }
        else {
            if self.currentPalyingIndex! > 0 {
                self.currentPalyingIndex = self.currentPalyingIndex! - 1
                self.loadSongFromURL()
            }
            else {
                // handle situation while reach at 0
            }
        }
    }
}

// Load Song
func loadSongFromURL(){

   let urlstring = songs[self.currentPalyingIndex]
   let strnew = urlstring.replacingOccurrences(of: "\"", with: "")
   downloadFileFromURL(url: strnew)
}