如何在iOS开发中从MP3文件中提取元数据

Question

我正在开发一个带有云存储的iOS音乐播放器。

我需要提取音乐信息，例如歌名、歌手和封面。

我有一个名为playit的操作，它可以播放和暂停mp3文件。它还应该使用与mp3文件相关联的元数据填充一些UILables和UIImage。问题是我无法从25个以上的不同mp3文件中提取元数据。以下是我的代码：

文件URL是正确的，因为音频播放器能够找到并播放它，但是我不知道为什么avmetadataitem无法获取元数据。

- (IBAction)playIt:(id)sender {
AVAudioPlayer *audioPlayer;
AVAsset *assest;

NSString * applicationPath = [[NSBundle mainBundle] resourcePath]; 
NSString *secondParentPath = [applicationPath stringByDeletingLastPathComponent];
NSString *soundFilePath = [[secondParentPath stringByAppendingPathComponent:@"fisal1407"] stringByAppendingPathComponent:[musicFiles objectForKey:@"show_id"] ];

NSURL *fileURL = [NSURL URLWithString:[soundFilePath stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding]];

assest = [AVURLAsset URLAssetWithURL:fileURL options:nil];
NSArray *metadata = [assest commonMetadata];
for (NSString *format in metadata) {
    for (AVMetadataItem *item in [assest metadataForFormat:format]) {
        if ([[item commonKey] isEqualToString:@"title"]) {
            filename.text = (NSString *)[item value];
            NSLog(@" title : %@", (NSString *)[item value]);
        } 
        if ([[item commonKey] isEqualToString:@"artist"]) {
            show_id.text = (NSString *)[item value];
        }
        if ([[item commonKey] isEqualToString:@"albumName"]) {
          //  _albumName = (NSString *)[item value];
        }
        if ([[item commonKey] isEqualToString:@"artwork"]) {
            NSData *data = [(NSDictionary *)[item value] objectForKey:@"data"];
            UIImage *img = [UIImage imageWithData:data]  ;
            imageView.image = img;
            continue;
         }
    }
 }

   if (audioPlayer == nil) {

    audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:&error];
    audioPlayer.numberOfLoops = -1;

   [audioPlayer play];
    [sender setImage:[UIImage imageNamed:@"player_044.gif"] forState:UIControlStateNormal];
   }
else
   {
    if (audioPlayer.isPlaying)
    {
        [sender setImage:[UIImage imageNamed:@"player_04.gif"] forState:UIControlStateNormal];
        [audioPlayer pause];
    } else {
        [sender setImage:[UIImage imageNamed:@"player_044.gif"] forState:UIControlStateNormal];
        [audioPlayer play];
    }
 }  
}

- user951297

---

将这段代码（包括下面答案中Alex建议的修改）与我找到的用于从m4a提取的代码集成在一起，以产生一个更通用的函数。您可以在包含我使用的m4a代码的问题的答案中找到它：https://dev59.com/_GYr5IYBdhLWcg3wAFg1#14046486 - 感谢所有参与者！ - Andy Weinstein

Answer 1

尝试

for (NSString *format in [asset availableMetadataFormats])

与其

NSArray *metadata = [assest commonMetadata];
for (NSString *format in metadata) {

- Alex