Приложение Сбой после выполнения фоновой выборки результатовHandler

Question

Я обновил наше приложение для iOS 7 и добавил функциональность фоновой выборки. Тем не менее, я замечаю некоторые сбои из-за этой функции. По завершении вызова фоновой выборки блок обработчика завершения выполняется с новыми или отсутствующими данными. Это приводит к вызову «layoutSubviews» моей настраиваемой навигации NavigationBar, и иногда приложение сбой со следующей трассировкой стека. Я не мог воспроизвести эту проблему самостоятельно, но постоянно получал эти аварийные журналы от наших пользователей. Любая помощь будет оценена по достоинству.

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) 

Answer 1

При выходе из приложения в фоновом режиме, он сохраняет снимок текущего представления в памяти, так что это может быть показано при двойном нажатии на кнопку домой. С функцией обновления фона iOS7 ((void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler) вы должны выполнить функцию completionHandler после завершения выполнения запроса на выборку.

Выполнение этой функции также вызывает обновления пользовательского интерфейса - [UIApplication _updateSnapshotAndStateRestorationArchiveForBackgroundEvent:saveState:exitIfCouldNotRestoreState:], а в вашем случае это вызывает вычисление кадра для UIWebView из фонового потока. UIWebView может быть обновлена ​​только из UIThread, так чтобы преодолеть эту аварию, я хотел бы предложить, чтобы обернуть completionHandler с исполнением на главной теме:

 
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler 
{ 
    void (^safeHandler)(UIBackgroundFetchResult) = ^(UIBackgroundFetchResult result){ 
     dispatch_async(dispatch_get_main_queue(), ^{ 
      completionHandler(result); 
     }); 
    }; 
    [someInstance doSomethingInBackground:userInfo withHandler:safeHandler]; 
} 

И вы никогда больше не придется беспокоиться, где вы вызываете completionHandler (сейчас safeHandler) из.