获取mp3图片在iOS 8上崩溃,但适用于iOS 7

Question

编辑:罪魁祸首是iOS 8,而不是模拟器(我没有意识到已经运行iOS 8)我已经重命名标题以反映这一点.

我很高兴使用这个SO问题的代码从mp3文件加载专辑封面.这是在我的带有iOS 7.1的iPhone 5上.

但后来我在iOS模拟器中跟踪崩溃到这段代码.进一步的调查显示,这个代码也在我的iPad上崩溃了.升级到iOS 8后,它在我的iPad上崩溃了.

看来包含图像的字典已损坏.

我创建了一个虚拟iOS项目,只加载专辑封面并得到相同的结果.下面是该viewcontroller的代码.

- (void) viewDidAppear:(BOOL)animated
{
    self.titleText = @"Overkill"; // Set song filename here
    NSString *filePath = [[NSBundle mainBundle] pathForResource:self.titleText ofType:@"mp3"];
    if (!filePath) {
        return;
    }
    NSURL *fileURL = [NSURL fileURLWithPath:filePath];

    NSLog(@"Getting song metadata for %@", self.titleText);
    AVAsset *asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];
    if (asset != nil) {
        NSArray *keys = [NSArray arrayWithObjects:@"commonMetadata", nil];
        [asset loadValuesAsynchronouslyForKeys:keys completionHandler:^{
            NSArray *artworks = [AVMetadataItem metadataItemsFromArray:asset.commonMetadata
                                                               withKey:AVMetadataCommonKeyArtwork
                                                              keySpace:AVMetadataKeySpaceCommon];
            UIImage *albumArtWork;

            for (AVMetadataItem *item in artworks) {
                if ([item.keySpace isEqualToString:AVMetadataKeySpaceID3]) {
                    NSDictionary *dict = [item.value copyWithZone:nil];

                    // **********
                    // Crashes here with SIGABRT. dict is not a valid dictionary.
                    // **********

                    if ([dict objectForKey:@"data"]) { 
                        albumArtWork = [UIImage imageWithData:[dict objectForKey:@"data"]];
                    }
                }
                else if ([item.keySpace isEqualToString:AVMetadataKeySpaceiTunes]) {
                    // This doesn't appear to get called for images set (ironically) in iTunes
                    albumArtWork = [UIImage imageWithData:[item.value copyWithZone:nil]];
                }
            }

            if (albumArtWork != nil) {
                dispatch_sync(dispatch_get_main_queue(), ^{
                    [self.albumArtImageView setImage:albumArtWork];
                });
            }

        }];
    }

}

我已经标记了崩溃线.它希望文件Overkill.mp3在捆绑中.我测试了多个mp3和m4a从iTunes和亚马逊导出,所以我知道文件本身是正确编码的.

在Xcode 6.0和6.1中测试过.

任何想法为什么它可以在iPhone上工作但不适用于模拟器或iPad？

编辑/更新:

记录item.value会显示差异.

在iPhone 5上(正常):

(lldb) po item.value
{
    MIME = JPG;
    data = <ffd8ffe0 .... several Kb of data ..... 2a17ffd9>;
    identifier = "";
    picturetype = Other;
}

在模拟器上(崩溃)

(lldb) po item.value
<ffd8ffe0 .... several Kb of data ..... 2a17ffd9>

因此,似乎在模拟器上没有字典,只有原始图稿.

更改代码不要期望字典,但item.value作为UIImage 工作!

        for (AVMetadataItem *item in artworks) {
            if ([item.keySpace isEqualToString:AVMetadataKeySpaceID3]) {
                NSData *newImage = [item.value copyWithZone:nil];
                albumArtWork = [UIImage imageWithData:newImage];
            }
            ...
        }

Answer 1

看来返回的数据结构中的iOS 8.改变value的AVMetadataItem对象不再是一本字典,但实际的原始UIImage数据.

添加测试可以NSFoundationVersionNumber解决问题.可能有一个更清洁的解决方案.

- (void) viewDidAppear:(BOOL)animated
{
    self.titleText = @"Overkill";
    NSString *filePath = [[NSBundle mainBundle] pathForResource:self.titleText ofType:@"mp3"];
    if (!filePath) {
        return;
    }
    NSURL *fileURL = [NSURL fileURLWithPath:filePath];

    NSLog(@"Getting song metadata for %@", self.titleText);
    AVAsset *asset = [AVURLAsset URLAssetWithURL:fileURL options:nil];
    if (asset != nil) {
        NSArray *keys = [NSArray arrayWithObjects:@"commonMetadata", nil];
        [asset loadValuesAsynchronouslyForKeys:keys completionHandler:^{
            NSArray *artworks = [AVMetadataItem metadataItemsFromArray:asset.commonMetadata
                                                               withKey:AVMetadataCommonKeyArtwork
                                                              keySpace:AVMetadataKeySpaceCommon];
            UIImage *albumArtWork;

            for (AVMetadataItem *item in artworks) {
                if ([item.keySpace isEqualToString:AVMetadataKeySpaceID3]) {

                    // *** WE TEST THE IOS VERSION HERE ***

                    if (TARGET_OS_IPHONE && NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_7_1) {
                        NSData *newImage = [item.value copyWithZone:nil];
                        albumArtWork = [UIImage imageWithData:newImage];
                    }
                    else {
                        NSDictionary *dict = [item.value copyWithZone:nil];
                        if ([dict objectForKey:@"data"]) {
                            albumArtWork = [UIImage imageWithData:[dict objectForKey:@"data"]];
                        }
                    }
                }
                else if ([item.keySpace isEqualToString:AVMetadataKeySpaceiTunes]) {
                    // This doesn't appear to get called for images set (ironically) in iTunes
                    albumArtWork = [UIImage imageWithData:[item.value copyWithZone:nil]];
                }
            }

            if (albumArtWork != nil) {
                dispatch_sync(dispatch_get_main_queue(), ^{
                    [self.albumArtImageView setImage:albumArtWork];
                });
            }

        }];
    }

}