我有一个Xamarin.Mac应用程序在尝试显示来自NSOutlineViewDelegate的GetView方法的警报时崩溃。
代码如下：
internal class ItemsDelegate : NSOutlineViewDelegate
{
public override NSView GetView(NSOutlineView outlineView, NSTableColumn tableColumn, NSObject item)
{
try
{
//code to return the NSView
}
catch (Exception ex)
{
NSAlert alert = new NSAlert();
alert.InformativeText = message;
alert.RunModal();
}
}
}
因此，它发生的是在代码中抛出一个受控异常以返回NSView。 当试图用NSAlert显示它时，在catch块和＆＃34; alert.RunModal（）＆＃34;执行时，应用程序崩溃。
崩溃异常如下：
Terminating app due to uncaught exception 'NSGenericException', reason: '-[NSAlert runModal] may not be invoked inside of transaction commit (usually this means it was invoked inside of a view's -drawRect: method.)'
First throw call stack:
(
0 CoreFoundation 0x00007fffca9976fb _exceptionPreprocess + 171
1 libobjc.A.dylib 0x00007fffdf33ba2a objc_exception_throw + 48
2 CoreFoundation 0x00007fffcaa149a5 +[NSException raise:format:] + 197
3 AppKit 0x00007fffc8d2eeaa _NSRunModal + 266
4 AppKit 0x00007fffc876c591 -[NSAlert runModal] + 270
5 macplastic 0x0000000107c97b39 xamarin_dyn_objc_msgSend + 217
6 ??? 0x0000000116c14f2b 0x0 + 4676734763
7 ??? 0x0000000116b06825 0x0 + 4675627045
8 ??? 0x0000000116a62808 0x0 + 4674955272
9 ??? 0x0000000116a62b8e 0x0 + 4674956174
10 macplastic 0x0000000107d9a340 mono_jit_runtime_invoke + 2272
11 macplastic 0x0000000107e4b3c8 do_runtime_invoke + 88
12 macplastic 0x0000000107e4b2d6 mono_runtime_invoke + 102
13 macplastic 0x0000000107c9583d xamarin_invoke_trampoline + 5725
14 macplastic 0x0000000107c965bd xamarin_arch_trampoline + 189
15 macplastic 0x0000000107c979b1 xamarin_x86_64_common_trampoline + 110
16 AppKit 0x00007fffc85b4f84 -[NSTableView(NSTableViewViewBased) makeViewForTableColumn:row:] + 76
17 AppKit 0x00007fffc85b495b -[NSTableRowData _addViewToRowView:atColumn:row:] + 308
18 AppKit 0x00007fffc85b469f -[NSTableRowData _addViewsToRowView:atRow:] + 204
19 AppKit 0x00007fffc85b2e47 -[NSTableRowData _initializeRowView:atRow:] + 390
20 AppKit 0x00007fffc85b144d -[NSTableRowData _addRowViewForVisibleRow:withPriorView:] + 398
21 AppKit 0x00007fffc85b1208 -[NSTableRowData _addRowViewForVisibleRow:withPriorRowIndex:inDictionary:withRowAnimation:] + 316
22 AppKit 0x00007fffc85b0030 -[NSTableRowData _unsafeUpdateVisibleRowEntries] + 1647
23 AppKit 0x00007fffc85af923 -[NSTableRowData updateVisibleRowViews] + 232
24 AppKit 0x00007fffc85af27a -[NSTableView layout] + 178
25 AppKit 0x00007fffc8d19afc _NSViewLayout + 450
26 AppKit 0x00007fffc8550074 -[NSView _doLayout] + 126
27 AppKit 0x00007fffc854fbf9 -[NSView _layoutSubtreeWithOldSize:] + 497
28 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
29 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
30 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
31 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
32 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
33 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
34 AppKit 0x00007fffc854fec7 -[NSView _layoutSubtreeWithOldSize:] + 1215
35 AppKit 0x00007fffc8d1fe89 -[NSView _layoutSubtreeIfNeededAndAllowTemporaryEngine:] + 1517
36 AppKit 0x00007fffc856e3f1 -[NSWindow(NSConstraintBasedLayout) _layoutViewTree] + 163
37 AppKit 0x00007fffc85dd52a -[NSWindow(NSConstraintBasedLayout) layoutIfNeeded] + 269
38 AppKit 0x00007fffc8d49f78 _NSWindowGetDisplayCycleObserver_block_invoke.6213 + 67
39 AppKit 0x00007fffc85eec89 _37+[NSDisplayCycle currentDisplayCycle]_block_invoke + 454
40 QuartzCore 0x00007fffd045a1ba _ZN2CA11Transaction19run_commit_handlersE18CATransactionPhase + 46
41 QuartzCore 0x00007fffd0561e10 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 160
42 QuartzCore 0x00007fffd0458d55 _ZN2CA11Transaction6commitEv + 475
43 AppKit 0x00007fffc88d0d99 _37+[NSDisplayCycle currentDisplayCycle]_block_invoke.31 + 323
44 CoreFoundation 0x00007fffca92dec7 _CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
45 CoreFoundation 0x00007fffca92de37 _CFRunLoopDoObservers + 391
46 CoreFoundation 0x00007fffca90ed79 _CFRunLoopRun + 873
47 CoreFoundation 0x00007fffca90e7b4 CFRunLoopRunSpecific + 420
48 HIToolbox 0x00007fffc9e9e2ac RunCurrentEventLoopInMode + 240
49 HIToolbox 0x00007fffc9e9e0e1 ReceiveNextEventCommon + 432
50 HIToolbox 0x00007fffc9e9df16 _BlockUntilNextEventMatchingListInModeWithFilter + 71
51 AppKit 0x00007fffc84a06cd _DPSNextEvent + 1093
52 AppKit 0x00007fffc8c17830 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 2730
53 AppKit 0x00007fffc849506d -[NSApplication run] + 926
54 AppKit 0x00007fffc845f983 NSApplicationMain + 1237
55 ??? 0x000000010c7cc9d2 0x0 + 4504472018
56 ??? 0x000000010c7cc5cd 0x0 + 4504470989
57 macplastic 0x0000000107d9a340 mono_jit_runtime_invoke + 2272
58 macplastic 0x0000000107e4b3c8 do_runtime_invoke + 88
59 macplastic 0x0000000107e4d8a0 mono_runtime_exec_main + 896
60 macplastic 0x0000000107e4d45d mono_runtime_run_main + 909
61 macplastic 0x0000000107cefca7 mono_jit_exec + 247
62 macplastic 0x0000000107cf2022 mono_main + 8098
63 macplastic 0x0000000107c982c4 xamarin_main + 980
64 macplastic 0x0000000107c98fd4 main + 36
65 macplastic 0x0000000107c7f944 start + 52
66 ??? 0x0000000000000002 0x0 + 2
)
libc++abi.dylib: terminating with uncaught exception of type NSException
任何帮助？
另外，为什么即使添加try / catch块，应用程序也会崩溃？有没有办法避免崩溃？
try
{
NSAlert alert = new NSAlert();
alert.InformativeText = message;
alert.RunModal();
}
catch (Exception ex)
{
//Nothing to do, we did our best to show the error message, avoid an unhandled crash.
}
非常感谢任何帮助。