边播边下有三套左右实现思路，本文使用AVPlayer + AVURLAsset实现。
概述
1. AVPlayer简介
- AVPlayer存在于AVFoundation中，可以播放视频和音频，可以理解为一个随身听
- AVPlayer的关联类：
- AVAsset：一个抽象类，不能直接使用，代表一个要播放的资源。可以理解为一个磁带子类AVURLAsset是根据URL生成的包含媒体信息的资源对象。我们就是要通过这个类的代理实现音频的边播边下的
- AVPlayerItem：可以理解为一个装在磁带盒子里的磁带
2. AVPlayer播放原理
- 给播放器设置好想要它播放的URL
- 播放器向URL所在的服务器发送请求，请求两个东西
- 所需音频片段的起始offset
- 所需的音频长度
- 服务器根据请求的内容，返回数据
- 播放器拿到数据拼装成文件
- 播放器从拼装好的文件中，找出现在需要播放的片段，进行播放
3. 边播边下的原理
实现边下边播，其实就是手动实现AVPlayer的上列播放过程。
- 当播放器需要预先缓存一些数据的时候，不让播放器直接向服务器发起请求，而是向我们自己写的某个类（暂且称之为播放器的秘书）发起缓存请求
- 秘书根据播放器的缓存请求的请求内容，向服务器发起请求。
- 服务器返回秘书所需的数据
- 秘书把服务器返回的数据写进本地的缓存文件中
- 当需要播放某段声音的时候，向秘书发出播放请求索要这段音频文件
- 秘书从本地的缓存文件中找到播放器播放请求所需片段，返回给播放器
- 播放器拿到数据开心滴播放
- 当整首歌都缓存完成以后，秘书需要把缓存文件拷贝一份，改个名字，这个文件就是我们所需要的本地持久化文件
- 下次播放器再播放歌曲的时候，先判断下本地有木有这个名字的文件，有则播放本地文件，木有则向秘书要数据
技术实现
OK，边播边下的原理知道了，我们可以正式写代码了建议先从文末链接处把Demo下载下来，对着Demo咱们慢慢道来
1. 类
共需要三个类：
- MusicPlayerManager：CEO。单例，负责整个工程所有的播放、暂停、下一曲、结束、判断应该播放本地文件还是从服务器拉数据之类的事情
- RequestLoader：就是上文所说的秘书，负责给播放器提供播放所需的音频片段，以及找人向服务器索要数据
- RequestTask：秘书的小弟。负责和服务器连接、向服务器请求数据、把请求回来的数据写到本地缓存文件、把写完的缓存文件移到持久化目录去。所有脏活累活都是他做。
2. 方法
先从小弟说起
2.1. RequestTask
2.1.0. 概说
如上文所说，小弟是负责做脏活累活的。 负责和服务器连接、向服务器请求数据、把请求回来的数据写到本地缓存文件、把写完的缓存文件移到持久化目录去
2.1.1. 初始化音频文件持久化文件夹 & 缓存文件
private func _initialTmpFile() {
do { try NSFileManager.defaultManager().createDirectoryAtPath(StreamAudioConfig.audioDicPath, withIntermediateDirectories: true, attributes: nil) } catch { print("creat dic false -- error:\(error)") }
if NSFileManager.defaultManager().fileExistsAtPath(StreamAudioConfig.tempPath) {
try! NSFileManager.defaultManager().removeItemAtPath(StreamAudioConfig.tempPath)
}
NSFileManager.defaultManager().createFileAtPath(StreamAudioConfig.tempPath, contents: nil, attributes: nil)
}
2.1.2. 与服务器建立连接请求数据
/**
连接服务器，请求数据（或拼range请求部分数据）（此方法中会将协议头修改为http）
- parameter offset: 请求位置
*/
public func set(URL url: NSURL, offset: Int) {
func initialTmpFile() {
try! NSFileManager.defaultManager().removeItemAtPath(StreamAudioConfig.tempPath)
NSFileManager.defaultManager().createFileAtPath(StreamAudioConfig.tempPath, contents: nil, attributes: nil)
}
_updateFilePath(url)
self.url = url
self.offset = offset
// 如果建立第二次请求，则需初始化缓冲文件
if taskArr.count >= 1 {
initialTmpFile()
}
// 初始化已下载文件长度
downLoadingOffset = 0
// 把stream://xxx的头换成http://的头
let actualURLComponents = NSURLComponents(URL: url, resolvingAgainstBaseURL: false)
actualURLComponents?.scheme = "http"
guard let URL = actualURLComponents?.URL else {return}
let request = NSMutableURLRequest(URL: URL, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringCacheData, timeoutInterval: 20.0)
// 若非从头下载，且视频长度已知且大于零，则下载offset到videoLength的范围（拼request参数）
if offset > 0 && videoLength > 0 {
request.addValue("bytes=\(offset)-\(videoLength - 1)", forHTTPHeaderField: "Range")
}
connection?.cancel()
connection = NSURLConnection(request: request, delegate: self, startImmediately: false)
connection?.setDelegateQueue(NSOperationQueue.mainQueue())
connection?.start()
}
2.1.3. 响应服务器的Response头
public func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) {
isFinishLoad = false
guard response is NSHTTPURLResponse else {return}
// 解析头部数据
let httpResponse = response as! NSHTTPURLResponse
let dic = httpResponse.allHeaderFields
let content = dic["Content-Range"] as? String
let array = content?.componentsSeparatedByString("/")
let length = array?.last
// 拿到真实长度
var videoLength = 0
if Int(length ?? "0") == 0 {
videoLength = Int(httpResponse.expectedContentLength)
} else {
videoLength = Int(length!)!
}
self.videoLength = videoLength
//TODO: 此处需要修改为真实数据格式 - 从字典中取
self.mimeType = "video/mp4"
// 回调
recieveVideoInfoHandler?(task: self, videoLength: videoLength, mimeType: mimeType!)
// 连接加入到任务数组中
taskArr.append(connection)
// 初始化文件传输句柄
fileHandle = NSFileHandle.init(forWritingAtPath: StreamAudioConfig.tempPath)
}
2.1.4. 处理服务器返回的数据 - 写入缓存文件中
public func connection(connection: NSURLConnection, didReceiveData data: NSData) {
// 寻址到文件末尾
self.fileHandle?.seekToEndOfFile()
self.fileHandle?.writeData(data)
self.downLoadingOffset += data.length
self.receiveVideoDataHandler?(task: self)
// print("线程 - \(NSThread.currentThread())")
// 注意，这里用子线程有问题
let queue = dispatch_queue_create("com.azen.taskConnect", DISPATCH_QUEUE_SERIAL)
dispatch_async(queue) {
// // 寻址到文件末尾
// self.fileHandle?.seekToEndOfFile()
// self.fileHandle?.writeData(data)
// self.downLoadingOffset += data.length
// self.receiveVideoDataHandler?(task: self)
// let thread = NSThread.currentThread()
// print("线程 - \(thread)")
}
2.1.5. 服务器文件返回完毕，把缓存文件放入持久化文件夹
public func connectionDidFinishLoading(connection: NSURLConnection) {
func tmpPersistence() {
isFinishLoad = true
let fileName = url?.lastPathComponent
// let movePath = audioDicPath.stringByAppendingPathComponent(fileName ?? "undefine.mp4")
let movePath = StreamAudioConfig.audioDicPath + "/\(fileName ?? "undefine.mp4")"
_ = try? NSFileManager.defaultManager().removeItemAtPath(movePath)
var isSuccessful = true
do { try NSFileManager.defaultManager().copyItemAtPath(StreamAudioConfig.tempPath, toPath: movePath) } catch {
isSuccessful = false
print("tmp文件持久化失败")
}
if isSuccessful {
print("持久化文件成功！路径 - \(movePath)")
}
}
if taskArr.count < 2 {
tmpPersistence()
}
receiveVideoFinishHanlder?(task: self)
}
其他
其他方法包括断线重连以及公开一个cancel方法cancel掉和服务器的连接
2.2. RequestLoader
2.2.0. 概说
秘书要干的最主要的事情就是响应播放器老大的号令，所有方法都是围绕着播放器老大来的。秘书需要遵循AVAssetResourceLoaderDelegate协议才能被录用。
2.2.1. 代理方法，播放器需要缓存数据的时候，会调这个方法
这个方法其实是播放器在说：小秘呀，我想要这段音频文件。你能现在给我还是等等给我啊？
一定要返回：true，告诉播放器，我等等给你。
然后，立马找本地缓存文件里有木有这段数据，有把数据拿给播放器，如果木有，则派秘书的小弟向服务器要。
具体实现代码有点多，这里就不全部贴出来了。可以去看看文末的Demo记得赏颗星哟~
/**
播放器问：是否应该等这requestResource加载完再说？
这里会出现很多个loadingRequest请求， 需要为每一次请求作出处理
- parameter resourceLoader: 资源管理器
- parameter loadingRequest: 每一小块数据的请求
- returns: <#return value description#>
*/
public func resourceLoader(resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool {
// 添加请求到队列
pendingRequset.append(loadingRequest)
// 处理请求
_dealWithLoadingRequest(loadingRequest)
print("----\(loadingRequest)")
return true
}
2.2.2. 代理方法，播放器关闭了下载请求
/**
播放器关闭了下载请求
播放器关闭一个旧请求，都会发起一到多个新请求，除非已经播放完毕了
- parameter resourceLoader: 资源管理器
- parameter loadingRequest: 待关请求
*/
public func resourceLoader(resourceLoader: AVAssetResourceLoader, didCancelLoadingRequest loadingRequest: AVAssetResourceLoadingRequest) {
guard let index = pendingRequset.indexOf(loadingRequest) else {return}
pendingRequset.removeAtIndex(index)
}
2.3. MusicPlayerManager
2.3.0. 概说
负责调度所有播放器的，负责App中的一切涉及音频播放的事件
唔。。犯个小懒。。代码直接贴上来咯要赶不上楼下的538路公交啦谢谢大家体谅哦
public class MusicPlayerManager: NSObject {
// public var status
public var currentURL: NSURL? {
get {
guard let currentIndex = currentIndex, musicURLList = musicURLList where currentIndex < musicURLList.count else {return nil}
return musicURLList[currentIndex]
}
}
/**播放状态，用于需要获取播放器状态的地方KVO*/
public var status: ManagerStatus = .Non
/**播放进度*/
public var progress: CGFloat {
get {
if playDuration > 0 {
let progress = playTime / playDuration
return progress
} else {
return 0
}
}
}
/**已播放时长*/
public var playTime: CGFloat = 0
/**总时长*/
public var playDuration: CGFloat = CGFloat.max
/**缓冲时长*/
public var tmpTime: CGFloat = 0
public var playEndConsul: (()->())?
/**强引用控制器，防止被销毁*/
public var currentController: UIViewController?
// private status
private var currentIndex: Int?
private var currentItem: AVPlayerItem? {
get {
if let currentURL = currentURL {
let item = getPlayerItem(withURL: currentURL)
return item
} else {
return nil
}
}
}
private var musicURLList: [NSURL]?
// basic element
public var player: AVPlayer?
private var playerStatusObserver: NSObject?
private var resourceLoader: RequestLoader = RequestLoader()
private var currentAsset: AVURLAsset?
private var progressCallBack: ((tmpProgress: Float?, playProgress: Float?)->())?
public class var sharedInstance: MusicPlayerManager {
struct Singleton {
static let instance = MusicPlayerManager()
}
// 后台播放
let session = AVAudioSession.sharedInstance()
do { try session.setActive(true) } catch { print(error) }
do { try session.setCategory(AVAudioSessionCategoryPlayback) } catch { print(error) }
return Singleton.instance
}
public enum ManagerStatus {
case Non, LoadSongInfo, ReadyToPlay, Play, Pause, Stop
}
}
// MARK: - basic public funcs
extension MusicPlayerManager {
/**
开始播放
*/
public func play(musicURL: NSURL?) {
guard let musicURL = musicURL else {return}
if let index = getIndexOfMusic(music: musicURL) { // 歌曲在队列中，则按顺序播放
currentIndex = index
} else {
putMusicToArray(music: musicURL)
currentIndex = 0
}
playMusicWithCurrentIndex()
}
public func play(musicURL: NSURL?, callBack: ((tmpProgress: Float?, playProgress: Float?)->())?) {
play(musicURL)
progressCallBack = callBack
}
public func next() {
currentIndex = getNextIndex()
playMusicWithCurrentIndex()
}
public func previous() {
currentIndex = getPreviousIndex()
playMusicWithCurrentIndex()
}
/**
继续
*/
public func goOn() {
player?.rate = 1
}
/**
暂停 - 可继续
*/
public func pause() {
player?.rate = 0
}
/**
停止 - 无法继续
*/
public func stop() {
endPlay()
}
}
// MARK: - private funcs
extension MusicPlayerManager {
private func putMusicToArray(music URL: NSURL) {
if musicURLList == nil {
musicURLList = [URL]
} else {
musicURLList!.insert(URL, atIndex: 0)
}
}
private func getIndexOfMusic(music URL: NSURL) -> Int? {
let index = musicURLList?.indexOf(URL)
return index
}
private func getNextIndex() -> Int? {
if let musicURLList = musicURLList where musicURLList.count > 0 {
if let currentIndex = currentIndex where currentIndex + 1 < musicURLList.count {
return currentIndex + 1
} else {
return 0
}
} else {
return nil
}
}
private func getPreviousIndex() -> Int? {
if let currentIndex = currentIndex {
if currentIndex - 1 >= 0 {
return currentIndex - 1
} else {
return musicURLList?.count ?? 1 - 1
}
} else {
return nil
}
}
/**
从头播放音乐列表
*/
private func replayMusicList() {
guard let musicURLList = musicURLList where musicURLList.count > 0 else {return}
currentIndex = 0
playMusicWithCurrentIndex()
}
/**
播放当前音乐
*/
private func playMusicWithCurrentIndex() {
guard let currentURL = currentURL else {return}
// 结束上一首
endPlay()
player = AVPlayer(playerItem: getPlayerItem(withURL: currentURL))
observePlayingItem()
}
/**
本地不存在，返回nil，否则返回本地URL
*/
private func getLocationFilePath(url: NSURL) -> NSURL? {
let fileName = url.lastPathComponent
let path = StreamAudioConfig.audioDicPath + "/\(fileName ?? "tmp.mp4")"
if NSFileManager.defaultManager().fileExistsAtPath(path) {
let url = NSURL.init(fileURLWithPath: path)
return url
} else {
return nil
}
}
private func getPlayerItem(withURL musicURL: NSURL) -> AVPlayerItem {
if let locationFile = getLocationFilePath(musicURL) {
let item = AVPlayerItem(URL: locationFile)
return item
} else {
let playURL = resourceLoader.getURL(url: musicURL)! // 转换协议头
let asset = AVURLAsset(URL: playURL)
currentAsset = asset
asset.resourceLoader.setDelegate(resourceLoader, queue: dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0))
let item = AVPlayerItem(asset: asset)
return item
}
}
private func setupPlayer(withURL musicURL: NSURL) {
let songItem = getPlayerItem(withURL: musicURL)
player = AVPlayer(playerItem: songItem)
}
private func playerPlay() {
player?.play()
}
private func endPlay() {
status = ManagerStatus.Stop
player?.rate = 0
removeObserForPlayingItem()
player?.replaceCurrentItemWithPlayerItem(nil)
resourceLoader.cancel()
currentAsset?.resourceLoader.setDelegate(nil, queue: nil)
progressCallBack = nil
resourceLoader = RequestLoader()
playDuration = 0
playTime = 0
playEndConsul?()
player = nil
}
}
extension MusicPlayerManager {
public override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer) {
guard object is AVPlayerItem else {return}
let item = object as! AVPlayerItem
if keyPath == "status" {
if item.status == AVPlayerItemStatus.ReadyToPlay {
status = .ReadyToPlay
print("ReadyToPlay")
let duration = item.duration
playerPlay()
print(duration)
} else if item.status == AVPlayerItemStatus.Failed {
status = .Stop
print("Failed")
stop()
}
} else if keyPath == "loadedTimeRanges" {
let array = item.loadedTimeRanges
guard let timeRange = array.first?.CMTimeRangeValue else {return} // 缓冲时间范围
let totalBuffer = CMTimeGetSeconds(timeRange.start) + CMTimeGetSeconds(timeRange.duration) // 当前缓冲长度
tmpTime = CGFloat(tmpTime)
print("共缓冲 - \(totalBuffer)")
let tmpProgress = tmpTime / playDuration
progressCallBack?(tmpProgress: Float(tmpProgress), playProgress: nil)
}
}
private func observePlayingItem() {
guard let currentItem = self.player?.currentItem else {return}
// KVO监听正在播放的对象状态变化
currentItem.addObserver(self, forKeyPath: "status", options: NSKeyValueObservingOptions.New, context: nil)
// 监听player播放情况
playerStatusObserver = player?.addPeriodicTimeObserverForInterval(CMTimeMake(1, 1), queue: dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), usingBlock: { [weak self] (time) in
guard let `self` = self else {return}
// 获取当前播放时间
self.status = .Play
let currentTime = CMTimeGetSeconds(time)
let totalTime = CMTimeGetSeconds(currentItem.duration)
self.playDuration = CGFloat(totalTime)
self.playTime = CGFloat(currentTime)
print("current time ---- \(currentTime) ---- tutalTime ---- \(totalTime)")
self.progressCallBack?(tmpProgress: nil, playProgress: Float(self.progress))
if totalTime - currentTime < 0.1 {
self.endPlay()
}
}) as? NSObject
// 监听缓存情况
currentItem.addObserver(self, forKeyPath: "loadedTimeRanges", options: NSKeyValueObservingOptions.New, context: nil)
}
private func removeObserForPlayingItem() {
guard let currentItem = self.player?.currentItem else {return}
currentItem.removeObserver(self, forKeyPath: "status")
if playerStatusObserver != nil {
player?.removeTimeObserver(playerStatusObserver!)
playerStatusObserver = nil
}
currentItem.removeObserver(self, forKeyPath: "loadedTimeRanges")
}
}
public struct StreamAudioConfig {
static let audioDicPath: String = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true).last! + "/streamAudio" // 缓冲文件夹
static let tempPath: String = audioDicPath + "/temp.mp4" // 缓冲文件路径 - 非持久化文件路径 - 当前逻辑下，有且只有一个缓冲文件
}
iOS音频边播边下Demo，戳这里~
如果对大家有点小帮助，记得赏颗Star哦~ 谢啦~