TL;DR：如果我将视频存储在 Assets.xcassets 中，我该如何播放？
我有大约 50 个视频想要存储在应用程序中。然后，我将使用按需资源获取来使我的应用程序大小更轻。但我只能通过将视频保存在 Assets.xcassets 中来实现这一点。而且我找不到从那里加载视频的方法，因为 AVPlayer 似乎只接受 url，而且我不确定如何为这样的本地存储资产获取它。
更新：
所以我做了进一步的挖掘，发现实际上不可能将视频存储在资产目录中并且仍然能够使用它们。我最终不得不将它们从资产目录中移出。至于按需取资源，目录外的资源还是可以的。你可以找到类似的方法here。
【问题讨论】：
现在可以在 Assets.xcassets 中加载视频并且仍然可以播放它们。 在 Xcode 12.0.1 Swift 5 上测试
import UIKit
import AVKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
func createLocalUrl(for filename: String, ofType: String) -> URL? {
let fileManager = FileManager.default
let cacheDirectory = fileManager.urls(for: .cachesDirectory, in: .userDomainMask)[0]
let url = cacheDirectory.appendingPathComponent("\(filename).\(ofType)")
guard fileManager.fileExists(atPath: url.path) else {
guard let video = NSDataAsset(name: filename) else { return nil }
fileManager.createFile(atPath: url.path, contents: video.data, attributes: nil)
return url
}
return url
}
@IBAction func playLocalVideo(_ sender: Any) {
guard let videoURL = createLocalUrl(for: "video", ofType: "mp4") else {
return
}
// Create an AVPlayer, passing it the local video url path
let player = AVPlayer(url: videoURL as URL)
let controller = AVPlayerViewController()
controller.player = player
present(controller, animated: true) {
player.play()
}
}
}
归功于如何创建本地网址：https://stackoverflow.com/a/39748919/4267092
【讨论】：
尝试使用 AVAsset，如 Apple Developer Documentation 中所述。
AVPlayerItem 可以加载 AVAsset 并播放它。加载 AVAssets 文档中的 sn-p：
func prepareToPlay() {
let url: URL = // Local or Remote Asset URL
let asset = AVAsset(url: url)
let assetKeys = [
"playable",
"hasProtectedContent"
]
// Create a new AVPlayerItem with the asset and an
// array of asset keys to be automatically loaded
playerItem = AVPlayerItem(asset: asset,
automaticallyLoadedAssetKeys: assetKeys)
// Register as an observer of the player item's status property
playerItem.addObserver(self,
forKeyPath: #keyPath(AVPlayerItem.status),
options: [.old, .new],
context: &playerItemContext)
// Associate the player item with the player
player = AVPlayer(playerItem: playerItem)
}
获取资产的 URL 可能看起来像这样：
let urlpath = Bundle.main.path(forResource: "myvideo", ofType: "mp4")
let url = NSURL.fileURL(withPath: urlpath!)
【讨论】：
您可以在资产目录中存储您喜欢的任何数据。但是，您只能将其加载为NSDataAsset，这会给您一个NSData。结果，您做了一些 URL 资源处理程序恶作剧来获取直接从 NSData 读取的 URL。
事情是这样的。
let videoUrl = URL(string: "my-custom-scheme-not-important://\(assetName)")!
let asset = AVURLAsset(url: videoUrl)
guard let dataAsset = NSDataAsset(name: assetName) else {
fatalError("Data asset not found with name \(assetName)")
}
let resourceDelegate = DataAssetAVResourceLoader(dataAsset: dataAsset)
assetLoaderDelegate = resourceDelegate
asset.resourceLoader.setDelegate(resourceDelegate, queue: .global(qos: .userInteractive))
let item = AVPlayerItem(asset: asset)
...
@objc
fileprivate class DataAssetAVResourceLoader: NSObject, AVAssetResourceLoaderDelegate {
let dataAsset: NSDataAsset
let data: Data
init(dataAsset: NSDataAsset) {
self.dataAsset = dataAsset
data = dataAsset.data
}
@objc
public func resourceLoader(_ resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool {
if let infoRequest = loadingRequest.contentInformationRequest {
infoRequest.contentType = kUTTypeQuickTimeMovie as String
infoRequest.contentLength = Int64(data.count)
infoRequest.isByteRangeAccessSupported = true
}
if let dataRequest = loadingRequest.dataRequest {
let range = Range(NSRange(location: Int(dataRequest.requestedOffset), length: dataRequest.requestedLength))!
dataRequest.respond(with: data.subdata(in:range))
loadingRequest.finishLoading()
return true
}
return false
}
}
【讨论】：
根据 Marc Palmer 的回答，我想出了以下解决方案，它有点“更快捷”。
我扩展了NSDataAsset 以符合AVAssetResourceLoaderDelegate 协议，我扩展了AVURLAsset 以使用NSDataAsset 进行初始化。
代码的最后一行使用了一点点 Objective-C 的魔法来保留委托，因为 AVURLAsset 的 ResourceLoader 不这样做，而且 Swift 不允许你在扩展中定义 vars。因为AVURLAsset 是一个Objective-C 类，所以这应该不是问题。
您可以在this post 中阅读有关objc_setAssociatedObject 的更多信息。
import Foundation
import AVFoundation
#if os(macOS)
import AppKit
#else
import UIKit
#endif
extension NSDataAsset:AVAssetResourceLoaderDelegate{
@objc public func resourceLoader(_ resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool {
if let infoRequest = loadingRequest.contentInformationRequest{
infoRequest.contentType = typeIdentifier
infoRequest.contentLength = Int64(data.count)
infoRequest.isByteRangeAccessSupported = true
}
if let dataRequest = loadingRequest.dataRequest{
dataRequest.respond(with: data.subdata(in:Int(dataRequest.requestedOffset) ..< Int(dataRequest.requestedOffset) + dataRequest.requestedLength))
loadingRequest.finishLoading()
return true
}
return false
}
}
extension AVURLAsset{
public convenience init?(_ dataAsset:NSDataAsset){
guard let name = dataAsset.name.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed),
let url = URL(string:"NSDataAsset://\(name))")
else {return nil}
self.init(url:url) // not really used!
self.resourceLoader.setDelegate(dataAsset, queue: .main)
// Retain the weak delegate for the lifetime of AVURLAsset
objc_setAssociatedObject(self, "AVURLAsset+NSDataAsset", dataAsset, .OBJC_ASSOCIATION_RETAIN)
}
【讨论】：