objective-c - 检索 iTunes 轨道图稿图像时出现错误。有时它说这不是图像

Question

我有以下代码来检索 currentTrack 的插图(使用 iTunes.h):

iTunesArtwork *iTunesArtwork = [[iTunes.currentTrack artworks] objectAtIndex:0];
NSImage *artwork = iTunesArtwork.data;                   
if (artwork != nil){
    [_musicImageView setImage:artwork];
}

它适用于大多数轨道，但有时它会给我这个错误(即使轨道有图像):

NSImageCell's object value must be an NSImage.
2012-12-28 00:22:12.217 App[3256:303] (
    0   CoreFoundation                      0x00007fff904360a6 __exceptionPreprocess + 198
    1   libobjc.A.dylib                     0x00007fff8d5bf3f0 objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff90435e7c +[NSException raise:format:] + 204
    3   AppKit                              0x00007fff9747c31b -[NSImageCell setObjectValue:] + 106
    4   AppKit                              0x00007fff974b8563 -[NSImageView setImage:] + 90
    5   App                                 0x0000000100001b38 -[AppDelegate setupPlayer] + 600
    6   Foundation                          0x00007fff8d10c513 __NSFireTimer + 96
    7   CoreFoundation                      0x00007fff903f2da4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
    8   CoreFoundation                      0x00007fff903f28bd __CFRunLoopDoTimer + 557
    9   CoreFoundation                      0x00007fff903d8099 __CFRunLoopRun + 1513
    10  CoreFoundation                      0x00007fff903d76b2 CFRunLoopRunSpecific + 290
    11  HIToolbox                           0x00007fff939e40a4 RunCurrentEventLoopInMode + 209
    12  HIToolbox                           0x00007fff939e3e42 ReceiveNextEventCommon + 356
    13  HIToolbox                           0x00007fff939e3cd3 BlockUntilNextEventMatchingListInMode + 62
    14  AppKit                              0x00007fff97337613 _DPSNextEvent + 685
    15  AppKit                              0x00007fff97336ed2 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 128
    16  AppKit                              0x00007fff9732e283 -[NSApplication run] + 517
    17  AppKit                              0x00007fff972d2cb6 NSApplicationMain + 869
    18  App                                 0x0000000100001822 main + 34
    19  libdyld.dylib                       0x00007fff93cb77e1 start + 0
)

对正在发生的事情有什么想法吗？

Answer 1

确保它是一个图像——不仅仅是检查它是否不为零，这还不够。 h 文件中的类型一定不是对象真正具有的类型。它更像是......它应该是一个图像:D

if([artwork isKindOfClass:[NSImage class]]) {
    ....

<小时/>

来自评论。但这并不总是有效。嗯。不再发生崩溃，但有些图像没有显示。我们使用 rawData 作为后备:

//kind of like this
if(![artwork isKindOfClass:[NSImage class]]) {
    artwork = [[NSImage alloc] initWithData:tunesArtwork.rawData];
}
if([artwork isKindOfClass:[NSImage class]]) {
    ...
}