PDFDocument removePageAtIndex：不更新時工作到Mac OS X 10.11

Question

我使用PDFKit框架到我的可可應用程序的PDFViewer.When我想刪除的頁面的一個從PDFDocument的應用凍結在代碼

[[self pdfDocument] removePageAtIndex:0]; // can see this Problem only in Mac OS X 10.11 

行這完美的作品，當我在的Mac OS上運行的應用程序X 10.10

我讀了所有相關文件蘋果，但我還沒有得到任何解決方案。

這裏是回溯：

* thread #1: tid = 0x85e1, 0x00007fff92571f5e libsystem_kernel.dylib`__psynch_cvwait + 10, queue = 'com.apple.main-thread', stop reason = signal SIGTERM 
    frame #0: 0x00007fff92571f5e libsystem_kernel.dylib`__psynch_cvwait + 10 
    frame #1: 0x00000001006c05f7 libsystem_pthread.dylib`_pthread_cond_wait + 767 
    frame #2: 0x00007fff904c6e32 Foundation`-[__NSOperationInternal _waitUntilFinished:] + 131 
    frame #3: 0x00007fff904921fa Foundation`-[NSOperationQueue waitUntilAllOperationsAreFinished] + 254 
    * frame #4: 0x000000010017efe1 Neat`-[NRMPDFCoordinator waitUntilAllOperationsAreFinished](self=0x0000608000ad3be0, _cmd=0x00007fff8877e285) + 145 at NRMPDFCoordinator.m:1362 
    frame #5: 0x00000001000109cf Neat`-[NRMItemEditorDocument saveDocumentWithDelegate:didSaveSelector:contextInfo:](self=0x000060000094a190, _cmd=0x00007fff88777581, delegate=0x0000000000000000, didSaveSelector=0x0000000000000000, contextInfo=0x0000000000000000) + 1151 at NRMItemEditorDocument.m:325 
    frame #6: 0x000000010001018a Neat`-[NRMItemEditorDocument saveDocument:](self=0x000060000094a190, _cmd=0x00007fff8874cbb4, sender=0x00006080003a8b20) + 58 at NRMItemEditorDocument.m:234 
    frame #7: 0x0000000100013bef Neat`-[NRMItemEditorWindowController saveAndClose:](self=0x00006080003a8b20, _cmd=0x00000001002cf2d2, sender=0x000060000094a5b0) + 95 at NRMItemEditorWindowController.m:244 
    frame #8: 0x00007fff87068082 libsystem_trace.dylib`_os_activity_initiate + 75 
    frame #9: 0x00007fff87fc79b5 AppKit`-[NSApplication sendAction:to:from:] + 460 
    frame #10: 0x00007fff87fd9bb2 AppKit`-[NSControl sendAction:to:] + 86 
    frame #11: 0x00007fff87fd9adc AppKit`__26-[NSCell _sendActionFrom:]_block_invoke + 131 
    frame #12: 0x00007fff87068082 libsystem_trace.dylib`_os_activity_initiate + 75 
    frame #13: 0x00007fff87fd9a39 AppKit`-[NSCell _sendActionFrom:] + 144 
    frame #14: 0x00007fff87068082 libsystem_trace.dylib`_os_activity_initiate + 75 
    frame #15: 0x00007fff87fd805e AppKit`-[NSCell trackMouse:inRect:ofView:untilMouseUp:] + 2693 
    frame #16: 0x00007fff88020d1c AppKit`-[NSButtonCell trackMouse:inRect:ofView:untilMouseUp:] + 744 
    frame #17: 0x00007fff87fd6788 AppKit`-[NSControl mouseDown:] + 669 
    frame #18: 0x00007fff88524575 AppKit`-[NSWindow _handleMouseDownEvent:isDelayedEvent:] + 6322 
    frame #19: 0x00007fff88525559 AppKit`-[NSWindow _reallySendEvent:isDelayedEvent:] + 212 
    frame #20: 0x00007fff87f6ad31 AppKit`-[NSWindow sendEvent:] + 517 
    frame #21: 0x00007fff87eeaccb AppKit`-[NSApplication sendEvent:] + 2540 
    frame #22: 0x0000000100225f35 Neat`-[NRMApplication sendEvent:](self=0x00006000001205a0, _cmd=0x00007fff88749e04, event=0x0000608000725640) + 1141 at NRMApplication.m:95 
    frame #23: 0x00007fff87d51f3e AppKit`-[NSApplication run] + 796 
    frame #24: 0x00007fff87d1b162 AppKit`NSApplicationMain + 1176 
    frame #25: 0x0000000100012d67 Neat`main(argc=3, argv=0x00007fff5fbff718) + 119 at main.m:21 
    frame #26: 0x0000000100001e74 Neat`start + 52 

這裏是我使用PDFDocument的removePageAtIndex方法

-(NSError *)removePageOpImpl:(NRMPDFOperation *)op 
{ 
    NSLog(@"\n Inside removePageOpImpl Method ..."); 
    NSError* error = [self loadDocument]; 
    if(!error) 
    { 
     NSUInteger index = [self pageIndexForId:[op pageId]]; 
     NSLog(@"Page count: %ld", [self pageCount]); 
     if(index < [self pageCount]) 
     { 
      NSLog(@"PDF Document:-- %@", [self pdfDocument]); 
      NSLog(@"Index is: %ld", index); 
      @try { 

       [(PDFDocument *)[self pdfDocument] removePageAtIndex:index];//At this line the app getting freezed and control is ended. 

       NSLog(@"Page count after delete: %ld", [self pageCount]); 


      } 
      @catch (NSException *exception) { 
       NSLog(@"Exception: %@", exception); 
      } 
      @finally { 
       NSLog(@"Finally called"); 
       [[self mutablePageIdList] removeObjectAtIndex:index]; 
       [self updatePageLabelsFromIndex:index]; 
       [self updateChangeCount:NSChangeDone]; 
       self.contentsChanged = YES; 
      } 
     } 
     else 
     { 
      // TODO: error 
     } 
    } 
    return error; 
} 

任何人都可以請建議我可能是什麼問題的方法......還附上阻塞UI的隊列屏幕截圖

我嘗試在主隊列上應用dispatch_async到PDFDocument頁面刪除操作，如下所示

- (NSError *)removePageOpImpl:(NRMPDFOperation *)op 
{ 
    NSError* error = [self loadDocument]; 
    if(!error) 
    { 
     NSUInteger index = [self pageIndexForId:[op pageId]]; 
     if(index < [self pageCount]) 
     { 
       dispatch_async(dispatch_get_main_queue(), ^{ 
         [[self pdfDocument] removePageAtIndex:index]; 
         [[self mutablePageIdList] removeObjectAtIndex:index]; 
         [self updatePageLabelsFromIndex:index]; 
         [self updateChangeCount:NSChangeDone]; 
         self.contentsChanged = YES; 

         }); 
     } 
     else 
     { 
      // TODO: error 
     } 
    } 
    return error; 
} 

現在的應用程序沒有掛，但我陷入了另一個問題。我有其他的操作應該在removePageOpImpl操作後同步運行。但是它們在removePageOpImpl完成之前執行，它正在改變我的應用程序的行爲。你能建議我如何在removePageOpImpl後同步執行其他操作。我讀了關於完成處理程序，但在這種情況下，我很困惑如何使用它。

請建議

Answer 1

您已經創建了一個可愛的小僵局在這裏。

你的主線程等待操作完成，但操作（該軌跡示）...

在後臺線程上運行，正如你所看到的，它的等待最有可能僅從主線程發出信號的信號量。這對主線程具有諸如dispatch_sync之類的特徵。由於它發生在PDFDocument實現中，我想它會試圖確保它在返回給用戶之前在主線程上運行某些內容（讀寫器鎖

因此，您的主線程正在等待某個操作完成，並且該操作正在等待主線程完成它正在嘗試執行的操作經典死鎖

發生這種情況是因爲主線程啓動了保存，然後等待所有內容在完成之前完成（但其他一些內容工作也需要在主線程上運行）

你需要啓動保存爲異步操作，所以它不在ma上運行在等待操作完成時在線程中。然後，當完成保存時，如果您必須更新UI，則可以通過主線程上運行的完成塊或委託來報告其成功/失敗。