当用户从iPod库中选择音频时，我拥有一个MPMediaItem的引用。我使用以下方法获取该项的资产URL：
let url = item.valueForProperty(MPMediaItemPropertyAssetURL)
但是这并没有给我文件的确切物理位置，而是给了我关于iPod库的一个URL。
ipod-library://item/item.mp3?id=1840064795502796074
有没有一种方法可以从iPod库中获取歌曲的物理URL？
编辑 - 实际上，我想从物理文件中提取NSData并将其发送到我的后端服务器，因此我需要物理文件URL而不是相对URL。
MPmediaPickerController正在工作，我选择了歌曲并播放，但我不想播放这首歌。我尝试上传音频文件到服务器。我在列表音频中使用了MPMedia Picker视图，当我选择音频时，我将上传到服务器(HTTP)，我该怎么做？如何使用Swift代码访问媒体库？
参考 Krishna 的答案，使用 AVAssetExportSession 将 MPMediaItem 保存到文件中。在 Swift 3 中，您可以像以下这样做：
/// Export MPMediaItem to temporary file.
///
/// - Parameters:
/// - assetURL: The `assetURL` of the `MPMediaItem`.
/// - completionHandler: Closure to be called when the export is done. The parameters are a boolean `success`, the `URL` of the temporary file, and an optional `Error` if there was any problem. The parameters of the closure are:
///
/// - fileURL: The `URL` of the temporary file created for the exported results.
/// - error: The `Error`, if any, of the asynchronous export process.
func export(_ assetURL: URL, completionHandler: @escaping (_ fileURL: URL?, _ error: Error?) -> ()) {
let asset = AVURLAsset(url: assetURL)
guard let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetAppleM4A) else {
completionHandler(nil, ExportError.unableToCreateExporter)
return
}
let fileURL = URL(fileURLWithPath: NSTemporaryDirectory())
.appendingPathComponent(NSUUID().uuidString)
.appendingPathExtension("m4a")
exporter.outputURL = fileURL
exporter.outputFileType = "com.apple.m4a-audio"
exporter.exportAsynchronously {
if exporter.status == .completed {
completionHandler(fileURL, nil)
} else {
completionHandler(nil, exporter.error)
}
}
}
func exampleUsage(with mediaItem: MPMediaItem) {
if let assetURL = mediaItem.assetURL {
export(assetURL) { fileURL, error in
guard let fileURL = fileURL, error == nil else {
print("export failed: \(error)")
return
}
// use fileURL of temporary file here
print("\(fileURL)")
}
}
}
enum ExportError: Error {
case unableToCreateExporter
}
或者，在 Swift 2 中：
/// Export MPMediaItem to temporary file.
///
/// - Parameters:
/// - assetURL: The `assetURL` of the `MPMediaItem`.
/// - completionHandler: Closure to be called when the export is done. The parameters are a boolean `success`, the `URL` of the temporary file, and an optional `Error` if there was any problem. The parameters of the closure are:
///
/// - fileURL: The `URL` of the temporary file created for the exported results.
/// - error: The `Error`, if any, of the asynchronous export process.
func export(assetURL: NSURL, completionHandler: (NSURL?, ErrorType?) -> ()) {
let asset = AVURLAsset(URL: assetURL)
guard let exporter = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetAppleM4A) else {
completionHandler(nil, ExportError.unableToCreateExporter)
return
}
let fileURL = NSURL(fileURLWithPath: NSTemporaryDirectory())
.URLByAppendingPathComponent(NSUUID().UUIDString)!
.URLByAppendingPathExtension("m4a")
exporter.outputURL = fileURL
exporter.outputFileType = "com.apple.m4a-audio"
exporter.exportAsynchronouslyWithCompletionHandler {
if exporter.status == .Completed {
completionHandler(fileURL, nil)
} else {
completionHandler(nil, exporter.error)
}
}
}
func exampleUsage(with mediaItem: MPMediaItem) {
if let assetURL = mediaItem.assetURL {
export(assetURL) { fileURL, error in
guard let fileURL = fileURL where error == nil else {
print("export failed: \(error)")
return
}
// use fileURL of temporary file here
print("\(fileURL)")
}
}
}
enum ExportError: ErrorType {
case unableToCreateExporter
}
你可以看到，我将它放在了一个临时文件夹而不是文档文件夹中。此外，我使用 UUID 而不是自某个参考日期以来的秒数来生成临时文件。但基本思想是相同的。
-( void)mediaItemToData : (MPMediaItem * ) curItem
{
NSURL *url = [curItem valueForProperty: MPMediaItemPropertyAssetURL];
AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL: url options:nil];
AVAssetExportSession *exporter = [[AVAssetExportSession alloc] initWithAsset: songAsset
presetName:AVAssetExportPresetAppleM4A];
exporter.outputFileType = @"com.apple.m4a-audio";
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * myDocumentsDirectory = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
[[NSDate date] timeIntervalSince1970];
NSTimeInterval seconds = [[NSDate date] timeIntervalSince1970];
NSString *intervalSeconds = [NSString stringWithFormat:@"%0.0f",seconds];
NSString * fileName = [NSString stringWithFormat:@"%@.m4a",intervalSeconds];
NSString *exportFile = [myDocumentsDirectory stringByAppendingPathComponent:fileName];
NSURL *exportURL = [NSURL fileURLWithPath:exportFile];
exporter.outputURL = exportURL;
// do the export
// (completion handler block omitted)
[exporter exportAsynchronouslyWithCompletionHandler:
^{
int exportStatus = exporter.status;
switch (exportStatus)
{
case AVAssetExportSessionStatusFailed:
{
NSError *exportError = exporter.error;
NSLog (@"AVAssetExportSessionStatusFailed: %@", exportError);
break;
}
case AVAssetExportSessionStatusCompleted:
{
NSLog (@"AVAssetExportSessionStatusCompleted");
NSData *data = [NSData dataWithContentsOfFile: [myDocumentsDirectory
stringByAppendingPathComponent:fileName]];
[arrayMusic addObject:data];
data = nil;
break;
}
case AVAssetExportSessionStatusUnknown:
{
NSLog (@"AVAssetExportSessionStatusUnknown"); break;
}
case AVAssetExportSessionStatusExporting:
{
NSLog (@"AVAssetExportSessionStatusExporting"); break;
}
case AVAssetExportSessionStatusCancelled:
{
NSLog (@"AVAssetExportSessionStatusCancelled"); break;
}
case AVAssetExportSessionStatusWaiting:
{
NSLog (@"AVAssetExportSessionStatusWaiting"); break;
}
default:
{
NSLog (@"didn't get export status"); break;
}
}
}];
}
NSData/Data对象中（因为它们同时保存在内存中），而是通常流式传输音乐文件。 - Rob