Swift 编程中的 url 文件中没有运行 AVAudioPlayer

Question

我对 Swift 编程还很陌生，现在已经开始学习几周了。我正在测试 YouTube 教程中的 AVAudioPlayer，它运行良好。这是代码。

let filelocation  = NSString( string: NSBundle.mainBundle().pathForResource(self.navigationItem.title, ofType: "mp3")!)
player = AVAudioPlayer(contentsOfURL: NSURL( fileURLWithPath: filelocation as String)!, error: &error)

那些mp3文件放在项目里所以在本地播放。我将代码更改为以下代码以从 URL 获取 mp3 文件并在此处播放。但是没用。

let url : NSString = "https://ia601409.us.archive.org/20/items/UsaNationalAnthemFromSilo/silosinging-us-anthem_64kb.mp3"
let urlStr : NSString = url.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)!
player = AVAudioPlayer(contentsOfURL: NSURL( fileURLWithPath: urlStr as String)!, error: &error)

我在 player.prepareToPlay() 处遇到一个错误 "fatal error: unexpectedly found nil while unwrapping an Optional value"，值为 "error NSError? domain: "NSOSStatusErrorDomain" - 代码：2003334207 0x00007fc3e3e4b820"

我在想 NSURL(fileURLWithPath: urlStr as String)！是不正确的，所以它只给出零。关于如何纠正它的任何想法！谢谢。

Answer 1

您不能使用 NSURL(fileURLWithPath:) 方法从网络 link 创建 url。从 links 创建 url 时，您需要使用 NSURL(string:) 但您应该使用 dataTaskWithUrl 异步下载数据，如下所示：

import UIKit
import AVFoundation

class ViewController: UIViewController {
    var player:AVAudioPlayer!
    override func viewDidLoad() {
        super.viewDidLoad()
        let link = "https://ia601409.us.archive.org/20/items/UsaNationalAnthemFromSilo/silosinging-us-anthem_64kb.mp3"
        if let linkUrl = NSURL(string: link) {
            println(linkUrl)
            NSURLSession.sharedSession().dataTaskWithURL(linkUrl, completionHandler: { (data, response, error) -> Void in
                dispatch_async(dispatch_get_main_queue()) {
                    println("Finished downloading")
                    // you can use the data! here
                    if let data = data {
                        var error:NSError?
                        self.player = AVAudioPlayer(data: data, error: &error)
                        if let error = error {
                            println(error.description)
                        } else {
                            self.player.prepareToPlay()
                            self.player.play()
                        }
                        // there is data. do this
                    } else if let error = error {
                        println(error.description)
                    }
                }
            }).resume()
        }
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

Answer 2

你必须先预加载mp3，你可以试试这个：

var p: AVAudioPlayer?

override func viewDidLoad() {
        super.viewDidLoad()
        var errorPointer: NSErrorPointer = NSErrorPointer()
        var url = NSURL(string: "https://ia601409.us.archive.org/20/items/UsaNationalAnthemFromSilo/silosinging-us-anthem_64kb.mp3")
        var request:NSMutableURLRequest = NSMutableURLRequest(URL:url!)
        let conf: NSURLSessionConfiguration = NSURLSession.sharedSession().configuration
        let session = NSURLSession(configuration: conf)
        session.dataTaskWithRequest(request) {
            data, response, error in
            if error != nil {
                println("\(error)")
            }else {
                self.p = AVAudioPlayer(data: data, error: errorPointer)
            }
            }.resume()

    }

然后在一个动作中这样做：

@IBAction func pushButton(sender: AnyObject) {
        p!.prepareToPlay()
        p!.volume = 100
        p!.play()
    }

Swift 编程中的 url 文件中没有运行 AVAudioPlayer

AVAudioPlayer didn't run from url file in Swift Programming

nsurl

avaudioplayer

swift

Swift 编程中的 url 文件中没有 运行 AVAudioPlayer

AVAudioPlayer didn't run from url file in Swift Programming

nsurl

avaudioplayer

swift

Swift 编程中的 url 文件中没有运行 AVAudioPlayer