App stürzt ab, nachdem Hintergrundabruf abgeschlossen wurdeHandler

Question

Ich habe unsere App für iOS 7 aktualisiert und die Hintergrundabruffunktion hinzugefügt. Allerdings merke ich aufgrund dieser Funktion einige Abstürze. Nachdem der Aufruf des Hintergrundabrufs abgeschlossen ist, wird der Beendigungsabwicklungsblock mit entweder neuen/keinen Daten ausgeführt. Dies führt zu einem Aufruf von 'layoutSubviews' meiner benutzerdefinierten Navigation NavigationBar und manchmal stürzt App mit dem folgenden Stack-Trace ab. Ich konnte dieses Problem nicht selbst reproduzieren, sondern erhielt ständig diese Absturzprotokolle von unseren Benutzern. Jede Hilfe wäre willkommen.

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

Wenn Sie Ihre App im Hintergrund verlassen, speichert es die Momentaufnahme der aktuellen Ansicht auf den Speicher so kann gezeigt werden, wenn Sie die Taste nach Hause doppelklicken. Mit der iOS7-Hintergrundaktualisierungsfunktion ((void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler) müssen Sie die completionHandler-Funktion ausführen, nachdem Sie Ihre Abrufanforderung abgeschlossen haben.

Die Ausführung dieser Funktion löst auch Aktualisierungen der Benutzeroberfläche - [UIApplication _updateSnapshotAndStateRestorationArchiveForBackgroundEvent:saveState:exitIfCouldNotRestoreState:], und in Ihrem Fall löst er den Rahmen für eine UIWebView von einem Thread Hintergrund zu berechnen. UIWebView kann nur von der UIThread aktualisiert werden, so dass dieser Absturz überwinden, würde ich vorschlagen, die completionHandler mit der Ausführung auf dem Haupt-Thread zu wickeln:

 
- (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]; 
} 

Und Sie werden nicht mehr kümmern müssen, wo Sie die completionHandler aufrufen (jetzt safeHandler) aus.