objective-c – 获取mp3图片在iOS 8上崩溃,但适用于iOS 7

编辑：罪魁祸首是iOS 8,而不是模拟器(我没有意识到已经在运行iOS 8),我已经重命名了标题来反映这一点.

我很高兴地使用this SO question的代码从mp3文件加载专辑封面.这是在我的iPhone 5与iOS 7.1.

但是,我跟踪了在iOS模拟器中崩溃的代码.进一步的调查显示,这个代码也在我的iPad上坠毁.它升级到iOS 8后,在我的iPad上坠毁.

看来包含图像的字典已损坏.

我创建了一个虚拟的iOS项目,只加载专辑封面,得到相同的结果.以下是该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];
                });
            }

        }];
    }

}

我已经标记了崩溃的线.它期望一个文件Overkill.mp3在包中.我测试了多个mp3和m4a从iTunes和Amazon导出,所以我知道文件本身是正确的编码.

在Xcode 6.0和6.1中测试.

任何想法为什么它可以在iPhone上工作,而不是模拟器或iPad？

编辑/更新：

记录item.value显示差异.

在iPhone 5(作品)：

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

在模拟器(崩溃)

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

所以似乎在模拟器上没有字典,只是原始的作品.

将代码更改为不期望字典,但将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];
            }
            ...
        }

解决方法

似乎在iOS 8中返回的数据结构已经发生变化.AVMetadataItem对象的值不再是字典,而是实际的原始UIImage数据.

为NSFoundationVersionNumber添加测试可以解决问题.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 %@",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];
                });
            }

        }];
    }

}