我如何知道 Xcode Objective-C 中的错误在哪里引发?
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【中文标题】我如何知道 Xcode Objective-C 中的错误在哪里引发?【英文标题】:How I can know where raises the error in Xcode Objective-C? 【发布时间】:2015-04-02 10:26:28 【问题描述】:我是 Objective-C 的初学者,我正在努力处理在 ios 7.1 中运行但在 iOS 8 中崩溃的代码。
我如何从堆栈跟踪中知道问题出在哪里?
为什么代码在旧版本(iOS 7)中有效而在新版本中无效?
使用不正确的NSMutableDictionary
或NSArray
是否有问题?
- (NSDictionary*) MPNowPlayingInfoCenterNowPlayingInfo
NSMutableDictionary *info;
if (self.currentPlayable && self.currentPlayable.mediaItemProperties)
info = self.currentPlayable.mediaItemProperties.mutableCopy;
else
info = [NSMutableDictionary dictionaryWithCapacity:10];
// Set defaults if missing
NSArray* metadata = self.player.currentItem.asset.commonMetadata;
if (!info[MPMediaItemPropertyPlaybackDuration])
float _playbackDuration = self.currentPlayerItem ? CMTimeGetSeconds(self.currentPlayerItem.duration) : 0.0f;
NSNumber* playbackDuration = @(_playbackDuration);
info[MPMediaItemPropertyPlaybackDuration] = playbackDuration;
if (!info[MPNowPlayingInfoPropertyElapsedPlaybackTime])
float _elapsedPlaybackTime = self.currentPlayerItem ? CMTimeGetSeconds(self.currentPlayerItem.currentTime) : 0.0f;
NSNumber* elapsedPlaybackTime = @(_elapsedPlaybackTime);
info[MPNowPlayingInfoPropertyElapsedPlaybackTime] = elapsedPlaybackTime;
if (!info[MPMediaItemPropertyArtwork])
NSArray* artworkMetadata = [AVMetadataItem metadataItemsFromArray:metadata
withKey:AVMetadataCommonKeyArtwork
keySpace:AVMetadataKeySpaceCommon];
if (artworkMetadata.count > 0)
AVMetadataItem* artworkMetadataItem = artworkMetadata[0];
UIImage* artworkImage = [UIImage imageWithData:artworkMetadataItem.value[@"data"]];
MPMediaItemArtwork* artwork = [[MPMediaItemArtwork alloc] initWithImage:artworkImage];
info[MPMediaItemPropertyArtwork] = artwork;
if (!info[MPMediaItemPropertyTitle])
NSArray* _metadata = [AVMetadataItem metadataItemsFromArray:metadata withKey:AVMetadataCommonKeyTitle keySpace:AVMetadataKeySpaceCommon];
if (_metadata.count > 0)
AVMetadataItem* _metadataItem = _metadata[0];
info[MPMediaItemPropertyTitle] = _metadataItem.value;
if (!info[MPMediaItemPropertyAlbumTitle])
NSArray* _metadata = [AVMetadataItem metadataItemsFromArray:metadata withKey:AVMetadataCommonKeyAlbumName keySpace:AVMetadataKeySpaceCommon];
if (_metadata.count > 0)
AVMetadataItem* _metadataItem = _metadata[0];
info[MPMediaItemPropertyAlbumTitle] = _metadataItem.value;
if (!info[MPMediaItemPropertyArtist])
NSArray* _metadata = [AVMetadataItem metadataItemsFromArray:metadata withKey:AVMetadataCommonKeyArtist keySpace:AVMetadataKeySpaceCommon];
if (_metadata.count > 0)
AVMetadataItem* _metadataItem = _metadata[0];
info[MPMediaItemPropertyArtist] = _metadataItem.value;
return info;
这里是堆栈跟踪:
HelloCordova[20791:74393] THREAD WARNING: ['AudioPlayerPlugin'] took '248.958008' ms. Plugin should use a background thread.
2015-04-01 10:16:21.377 HelloCordova[20791:74903] Retrieving lock screen art...
2015-04-01 10:16:29.295 HelloCordova[20791:74903] Initializing lock screen art...
2015-04-01 10:16:29.296 HelloCordova[20791:74903] Creating MPMediaItemArtwork...
2015-04-01 10:16:29.322 HelloCordova[20791:74903] Done retrieving lock screen art.
2015-04-01 10:16:51.439 HelloCordova[20791:74393] -[__NSCFData objectForKeyedSubscript:]: unrecognized selector sent to instance 0x7ffb33e0fe80
Apr 1 10:16:51 Pourias-Mac.local rtcreporting[20791] <Info>: logging starts...
Apr 1 10:16:51 Pourias-Mac.local rtcreporting[20791] <Debug>: setMessageLoggingBlock: called
2015-04-01 10:16:51.618 HelloCordova[20791:74393] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFData objectForKeyedSubscript:]: unrecognized selector sent to instance 0x7ffb33e0fe80'
*** First throw call stack:
(
0 CoreFoundation 0x000000010241ea75 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x0000000104f96bb7 objc_exception_throw + 45
2 CoreFoundation 0x0000000102425d1d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
3 CoreFoundation 0x000000010237d9dc ___forwarding___ + 988
4 CoreFoundation 0x000000010237d578 _CF_forwarding_prep_0 + 120
5 HelloCordova 0x00000001021ce2a8 -[PRXPlayer MPNowPlayingInfoCenterNowPlayingInfo] + 2056
6 HelloCordova 0x00000001021d4549 -[NYPRPlayer MPNowPlayingInfoCenterNowPlayingInfo] + 57
7 HelloCordova 0x00000001021ce9e5 -[PRXPlayer setMPNowPlayingInfoCenterNowPlayingInfo] + 85
8 HelloCordova 0x00000001021d5acb -[NYPRPlayer refreshMetadata] + 43
9 HelloCordova 0x00000001021c4e02 -[AudioStreamHandler updateProgress] + 146
10 HelloCordova 0x00000001021c576b -[AudioStreamHandler observedPlayerDidObservePeriodicTimeInterval:] + 91
11 HelloCordova 0x00000001021cc85e -[PRXPlayer reportPlayerTimeIntervalToObservers] + 670
12 HelloCordova 0x00000001021caa4b -[PRXPlayer playerItemDidJumpTime:] + 91
13 CoreFoundation 0x00000001023ee7fc __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12
14 CoreFoundation 0x00000001022ee204 _CFXNotificationPost + 2484
15 AVFoundation 0x0000000103b4c0b2 __avplayeritem_fpItemNotificationCallback_block_invoke + 7447
16 libdispatch.dylib 0x00000001056b8186 _dispatch_call_block_and_release + 12
17 libdispatch.dylib 0x00000001056d7614 _dispatch_client_callout + 8
18 libdispatch.dylib 0x00000001056bfa1c _dispatch_main_queue_callback_4CF + 1664
19 CoreFoundation 0x0000000102386749 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
20 CoreFoundation 0x000000010234962b __CFRunLoopRun + 2043
21 CoreFoundation 0x0000000102348bc6 CFRunLoopRunSpecific + 470
22 GraphicsServices 0x0000000106735a58 GSEventRunModal + 161
23 UIKit 0x000000010280e580 UIApplicationMain + 1282
24 HelloCordova 0x000000010219a0e7 main + 71
25 libdyld.dylib 0x000000010570c145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
这个问题的一部分是 This question 的重复,但作为新手 iOS 开发人员,我什至不知道从哪里开始问我的问题,很抱歉重复的问题,但在其他问题中,我得到了自己的答案并检查了它作为正确答案。
【问题讨论】:
断点呢? Xcode doesn't show the line that causes a crash的可能重复 这里是发生错误的地方:[PRXPlayer MPNowPlayingInfoCenterNowPlayingInfo] + 2056 How can I debug 'unrecognized selector sent to instance' error的可能重复 【参考方案1】:问题是您试图获取objectForKey
的不是字典而是NSData
的东西。我这就是这一行:
UIImage* artworkImage = [UIImage imageWithData:artworkMetadataItem.value[@"data"]];
也许你可以在此处添加断点并打印出artworkMetadataItem.value
以查看它是哪种类型。
如果这不是问题,您可以尝试逐步运行代码以查看导致崩溃的语句。
希望这可行!告诉我进展如何
【讨论】:
是的,你提到的那一行是问题,我搜索了一下,发现this answer他们在iOS 8中改变了艺术品的数据类型 很高兴你能找到它 :) 很高兴我能帮上忙【参考方案2】:假设您使用的是 Xcode,您可以打开异常断点。这将导致应用程序在抛出异常时跳转到中断的行。
【讨论】:
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