执行后台获取完成处理程序后应用程序崩溃
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【中文标题】执行后台获取完成处理程序后应用程序崩溃【英文标题】：App Crashes after executing background fetch completionHandler 【发布时间】：2013-09-24 06:16:12 【问题描述】：我为 ios 7 更新了我们的应用程序并添加了后台获取功能。但是，由于此功能，我注意到一些崩溃。后台获取调用完成后，完成处理程序块将使用新数据/无数据执行。这会导致调用我的自定义导航 NavigationBar 的“layoutSubviews”，有时应用程序会因以下堆栈跟踪而崩溃。我自己无法重现此问题，但不断从我们的用户那里收到这些崩溃日志。任何帮助将不胜感激。
Thread 0 Crashed:
0 libsystem_platform.dylib 0x39cba486 _platform_memmove$VARIANT$Swift + 102
1 Foundation 0x2fce8f47 -[NSData(NSData) getBytes:range:] + 419
2 CoreFoundation 0x2f30637d CFDataGetBytes + 205
3 ImageIO 0x300e7357 CGImageReadGetBytesAtOffset + 283
4 ImageIO 0x300e7231 CGImageReadSessionGetBytes + 29
5 ImageIO 0x3022baeb read_fn + 23
6 ImageIO 0x300e7189 png_read_sig + 45
7 ImageIO 0x300e6e0d _cg_png_read_info + 33
8 ImageIO 0x300ef62f copyImageBlockSetPNG + 1123
9 ImageIO 0x300eec4b ImageProviderCopyImageBlockSetCallback + 539
10 CoreGraphics 0x2f43577d CGImageProviderCopyImageBlockSetWithOptions + 137
11 CoreGraphics 0x2f43a145 subImageProviderCopyImageBlockSet + 305
12 CoreGraphics 0x2f43577d CGImageProviderCopyImageBlockSetWithOptions + 137
13 CoreGraphics 0x2f435433 img_blocks_create + 383
14 CoreGraphics 0x2f4286fd img_data_lock + 1053
15 CoreGraphics 0x2f427ae1 CGSImageDataLock + 89
16 libRIP.A.dylib 0x2f774da7 ripc_AcquireImage + 99
17 libRIP.A.dylib 0x2f774131 ripc_DrawImage + 601
18 CoreGraphics 0x2f4279f3 CGContextDelegateDrawImage + 51
19 CoreGraphics 0x2f427879 CGContextDrawImage + 285
20 WebCore 0x373120db WebCore::GraphicsContext::drawNativeImage(CGImage*, WebCore::FloatSize const&, WebCore::ColorSpace, WebCore::FloatRect const&, WebCore::FloatRect const&, float, WebCore::CompositeOperator, WebCore::BlendMode, WebCore::ImageOrientation) + 1127
21 WebCore 0x37310e79 WebCore::BitmapImage::draw(WebCore::GraphicsContext*, WebCore::FloatRect const&, WebCore::FloatRect const&, WebCore::ColorSpace, WebCore::CompositeOperator, WebCore::BlendMode, WebCore::RespectImageOrientationEnum) + 349
22 WebCore 0x3735d897 WebCore::BitmapImage::draw(WebCore::GraphicsContext*, WebCore::FloatRect const&, WebCore::FloatRect const&, WebCore::ColorSpace, WebCore::CompositeOperator, WebCore::BlendMode) + 31
23 WebCore 0x3735892f WebCore::Image::drawTiled(WebCore::GraphicsContext*, WebCore::FloatRect const&, WebCore::FloatPoint const&, WebCore::FloatSize const&, WebCore::ColorSpace, WebCore::CompositeOperator, WebCore::BlendMode) + 499
24 WebCore 0x37358735 WebCore::GraphicsContext::drawTiledImage(WebCore::Image*, WebCore::ColorSpace, WebCore::IntRect const&, WebCore::IntPoint const&, WebCore::IntSize const&, WebCore::CompositeOperator, bool, WebCore::BlendMode) + 193
25 WebCore 0x3728bc11 WebCore::RenderBoxModelObject::paintFillLayerExtended(WebCore::PaintInfo const&, WebCore::Color const&, WebCore::FillLayer const*, WebCore::LayoutRect const&, WebCore::BackgroundBleedAvoidance, WebCore::InlineFlowBox*, WebCore::LayoutSize const&, WebCore::CompositeOperator, WebCore::RenderObject*) + 3321
26 WebCore 0x3728addd WebCore::RenderBox::paintFillLayers(WebCore::PaintInfo const&, WebCore::Color const&, WebCore::FillLayer const*, WebCore::LayoutRect const&, WebCore::BackgroundBleedAvoidance, WebCore::CompositeOperator, WebCore::RenderObject*) + 449
27 WebCore 0x3728ab41 WebCore::RenderBox::paintBackground(WebCore::PaintInfo const&, WebCore::LayoutRect const&, WebCore::BackgroundBleedAvoidance) + 317
28 WebCore 0x37289ee5 WebCore::RenderBox::paintBoxDecorations(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 329
29 WebCore 0x3728806f WebCore::RenderBlock::paintObject(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 55
30 WebCore 0x37289c3f WebCore::RenderBlock::paint(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 187
31 WebCore 0x37288cc9 WebCore::RenderBlock::paintFloats(WebCore::PaintInfo&, WebCore::LayoutPoint const&, bool) + 305
32 WebCore 0x3728813d WebCore::RenderBlock::paintObject(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 261
33 WebCore 0x37289c3f WebCore::RenderBlock::paint(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 187
34 WebCore 0x37288cfb WebCore::RenderBlock::paintFloats(WebCore::PaintInfo&, WebCore::LayoutPoint const&, bool) + 355
35 WebCore 0x3728813d WebCore::RenderBlock::paintObject(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 261
36 WebCore 0x37289c3f WebCore::RenderBlock::paint(WebCore::PaintInfo&, WebCore::LayoutPoint const&) + 187
37 WebCore 0x37288861 WebCore::RenderLayer::paintForegroundForFragmentsWithPhase(WebCore::PaintPhase, WTF::Vector<WebCore::LayerFragment, 1ul, WTF::CrashOnOverflow> const&, WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int, WebCore::RenderObject*) + 269
38 WebCore 0x372886e7 WebCore::RenderLayer::paintForegroundForFragments(WTF::Vector<WebCore::LayerFragment, 1ul, WTF::CrashOnOverflow> const&, WebCore::GraphicsContext*, WebCore::GraphicsContext*, WebCore::LayoutRect const&, bool, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int, WebCore::RenderObject*, bool, bool) + 235
39 WebCore 0x37286435 WebCore::RenderLayer::paintLayerContents(WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 1585
40 WebCore 0x37285ca9 WebCore::RenderLayer::paintLayer(WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 621
41 WebCore 0x372885d9 WebCore::RenderLayer::paintList(WTF::Vector<WebCore::RenderLayer*, 0ul, WTF::CrashOnOverflow>*, WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 101
42 WebCore 0x3728647f WebCore::RenderLayer::paintLayerContents(WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 1659
43 WebCore 0x37285ca9 WebCore::RenderLayer::paintLayer(WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 621
44 WebCore 0x372885d9 WebCore::RenderLayer::paintList(WTF::Vector<WebCore::RenderLayer*, 0ul, WTF::CrashOnOverflow>*, WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 101
45 WebCore 0x3728647f WebCore::RenderLayer::paintLayerContents(WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 1659
46 WebCore 0x37285ca9 WebCore::RenderLayer::paintLayer(WebCore::GraphicsContext*, WebCore::RenderLayer::LayerPaintingInfo const&, unsigned int) + 621
47 WebCore 0x372859b3 WebCore::RenderLayer::paint(WebCore::GraphicsContext*, WebCore::LayoutRect const&, unsigned int, WebCore::RenderObject*, WebCore::RenderRegion*, unsigned int) + 103
48 WebCore 0x3728541b WebCore::FrameView::paintContents(WebCore::GraphicsContext*, WebCore::IntRect const&) + 499
49 WebKit 0x37c4578d -[WebFrame(WebInternal) _drawRect:contentsOnly:] + 357
50 WebKit 0x37c455b9 -[WebhtmlView drawSingleRect:] + 137
51 WebKit 0x37c454db -[WebHTMLView drawRect:] + 43
52 WebCore 0x37284d93 -[WAKView _drawRect:context:lockFocus:] + 275
53 WebCore 0x37284ec7 -[WAKView _drawRect:context:lockFocus:] + 583
54 WebCore 0x37284ec7 -[WAKView _drawRect:context:lockFocus:] + 583
55 WebCore 0x37284ec7 -[WAKView _drawRect:context:lockFocus:] + 583
56 WebCore 0x37284ec7 -[WAKView _drawRect:context:lockFocus:] + 583
57 WebCore 0x37284c47 -[WAKView displayRect:] + 59
58 WebCore 0x37284c03 -[WAKWindow displayRect:] + 55
59 WebCore 0x37284b49 WebCore::TileCache::drawWindowContent(TileLayer*, CGContext*, CGRect) + 673
60 WebCore 0x37284525 WebCore::TileCache::drawLayer(TileLayer*, CGContext*) + 505
61 QuartzCore 0x317d3813 CABackingStoreUpdate_ + 1859
62 QuartzCore 0x318ad735 ___ZN2CA5Layer8display_Ev_block_invoke + 53
63 QuartzCore 0x317d30c3 x_blame_allocations + 83
64 QuartzCore 0x317d2d77 CA::Layer::display_() + 1119
65 QuartzCore 0x317b6969 CA::Layer::display_if_needed(CA::Transaction*) + 209
66 QuartzCore 0x317b6601 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 25
67 QuartzCore 0x317b600d CA::Context::commit_transaction(CA::Transaction*) + 229
68 QuartzCore 0x317b5e1f CA::Transaction::commit() + 315
69 UIKit 0x31d973c9 _UIWindowUpdateVisibleContextOrder + 209
70 UIKit 0x31d9729d +[UIWindow _prepareWindowsPassingTestForAppResume:] + 13
71 UIKit 0x31db0ac5 -[UIApplication _updateSnapshotAndStateRestorationArchiveForBackgroundEvent:saveState:exitIfCouldNotRestoreState:] + 201
72 UIKit 0x31db0d81 -[UIApplication _replyToBackgroundFetchRequestWithResult:remoteNotificationToken:sequenceNumber:updateApplicationSnapshot:] + 105
73 UIKit 0x31db138d __61-[UIApplication _handleOpportunisticFetchWithSequenceNumber:]_block_invoke + 37
74 MyApp 0x001456b7 -[List fetched:error:withBackgroundFetchCompletionHandler:] (List.m:421)
75 MyApp 0x00144f87 __71-[List fetchFromServerWithBackgroundFetchCompletionHandler:]_block_invoke (List.m:292)
76 MyApp 0x0021ed07 APICompletionBlock_block_invoke_6 (APIRequest.m:305)
77 libdispatch.dylib 0x39b8c103 _dispatch_call_block_and_release + 11
78 libdispatch.dylib 0x39b8c0ef _dispatch_client_callout + 23
79 libdispatch.dylib 0x39b8e9a9 _dispatch_main_queue_callback_4CF + 269
80 CoreFoundation 0x2f3785b9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
81 CoreFoundation 0x2f376e85 __CFRunLoopRun + 1309
82 CoreFoundation 0x2f2e1541 CFRunLoopRunSpecific + 525
83 CoreFoundation 0x2f2e1323 CFRunLoopRunInMode + 107
84 GraphicsServices 0x340182eb GSEventRunModal + 139
85 UIKit 0x31b981e5 UIApplicationMain + 1137
86 MyApp 0x0009f77f main (main.m:14)
【问题讨论】：
@Sohaib，还没有。我计划实施 Kobi M 的建议并发布一个版本。在新版本中观察到崩溃后将更新此问题。 @Alexander Smirov，我已经在其中一个版本中尝试过 Kobi 的建议，但崩溃仍在发生。 我没试过。但是，iOS 试图在后台获取周期期间更新其快照对我来说似乎很奇怪。我想知道是否有可能因为您传入了 UIBackgroundFetchResultNewData 而触发了此例程？如果您改为发送 UIBackgroundFetchResultNoData 会有所帮助吗？另一个可能的解决方法是设置 Web 视图的快照视图，并在应用程序进入后台时将其插入到 Web 视图上方。所以希望快照例程在执行后台获取时不会出现恐慌。 【参考方案1】：
当您将应用程序置于后台时，它会将当前视图的快照保存到内存中，以便在您双击主页按钮时显示它。
使用 iOS7 后台刷新功能 ((void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler)，您必须在执行完 fetch 请求后执行 completionHandler 函数。
该函数的执行还会触发对 UI 的更新 - [UIApplication _updateSnapshotAndStateRestorationArchiveForBackgroundEvent:saveState:exitIfCouldNotRestoreState:]，在您的情况下，它会触发从 后台线程 计算 UIWebView 的框架。
UIWebView 只能从 UIThread 更新，因此为了克服这种崩溃，我建议将 completionHandler 包装在主线程上执行：
您将不再需要担心从哪里调用completionHandler（现在是safeHandler）。
【讨论】：
这是一个很好的解决方案。根据 OP 的堆栈跟踪，看起来这是后台获取，而不是远程通知。但同样的代码仍然有效！ 对我来说似乎不正确。堆栈跟踪似乎发生在主线程中（“main”和“UIAppllicationMain”在那里）。但第一部分是正确的：它发生是因为从后台获取返回时 WebView 更新出现故障。 @Gnawer 主线程在操作不完整时崩溃。此操作未完成，因为在另一个线程中调用了完成处理程序，应用程序的处理器时间现已结束。 谢谢 - 由于 UI 中有一些广告，我的后台提取完成处理程序遇到了这个确切的问题。以上是关于执行后台获取完成处理程序后应用程序崩溃的主要内容，如果未能解决你的问题，请参考以下文章
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