ios – 如何在使用avplayer播放音频时将音频缓存到本地

我实现如下：

let fileUrl =  NSURL(string: strUrl)!
    let asset = AVURLAsset(URL: fileUrl)
    asset.resourceLoader.setDelegate(self,queue:dispatch_queue_create("AVARLDelegateDemo loader",nil))
    self.pendingRequests = [AVAssetResourceLoadingRequest]()

    asset.loadValuesAsynchronouslyForKeys(["playable"]){
        dispatch_async( dispatch_get_main_queue()){
            self.prepareToPlayAsset(asset,requestedKeys: ["playable"])
        }
    }


  func resourceLoader(resourceLoader: AVAssetResourceLoader,shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool {
    .......
    return false
}

当url是http / https时,它不会调用resourceLoader(resourceLoader：AVAssetResourceLoader,shouldWaitForLoadingOfRequestedResource …. –,当url是自定义的(例如：’test’)时,它调用resourceLoader(resourceLoader：AVAssetResourceLoader,shouldWaitForLoadingOfRequestedResource …

谁知道原因,resourceLoader不支持http / https吗？