如何设置 CG_CONTEXT_SHOW_BACKTRACE 环境变量？

我的视野里有三个按钮。在 viewDidLoad () : button.layer.cornerRadius = 20中设置角 Radus 之后，我在日志中得到以下错误消息:

 <Error>: CGContextSaveGState: invalid context 0x0.
If you want to see the backtrace, please set
CG_CONTEXT_SHOW_BACKTRACE environmental variable.

问题:

• 如何设置 CG _ CONTEXT _ SHOW _ BACKTRACE 环境变量？
• 或者我该如何修复这个警告？

好了，我已经从信息中反向追踪到了。这对我来说没有任何意义。请帮助..。

Aug  7 14:27:00  <Error>: CGContextSaveGState: invalid context 0x0. Backtrace:
<-[UIStatusBarItemView updateContentsAndWidth]+33>
<-[UIStatusBarItemView initWithItem:data:actions:style:]+477>
<+[UIStatusBarItemView createViewForItem:withData:actions:foregroundStyle:]+134>
<-[UIStatusBarLayoutManager _createViewForItem:withData:actions:]+163>
<-[UIStatusBarLayoutManager _prepareEnabledItemType:withEnabledItems:withData:actions:itemAppearing:itemDisappearing:]+36
<-[UIStatusBarLayoutManager prepareEnabledItems:withData:actions:]+92>
<-[UIStatusBarForegroundView _setStatusBarData:actions:animated:]+797>
<-[UIStatusBarForegroundView setStatusBarData:actions:animated:]+332>
<__51-[UIStatusBar _prepareToSetStyle:animation:forced:]_block_invoke+360>
<+[UIView(Animation) performWithoutAnimation:]+65>
<-[UIStatusBar _prepareToSetStyle:animation:forced:]+866>
<-[UIStatusBar _requestStyleAttributes:animationParameters:forced:]+391>
<-[UIStatusBar requestStyle:animationParameters:forced:]+437>
<-[UIStatusBar requestStyle:animated:forced:]+90>
<-[UIStatusBar _evaluateServerRegistration]+250>
<__45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke+590>
<-[UIView(Hierarchy) _postMovedFromSuperview:]+544>
<-[UIView(Internal) _addSubview:positioned:relativeTo:]+1967>
<-[UIStatusBarWindow setStatusBar:]+288>
<-[UIApplication _createStatusBarWithRequestedStyle:orientation:hidden:]+340>
<-[UIApplication _runWithMainScene:transitionContext:completion:]+950>
<-[UIApplication workspaceDidEndTransaction:]+188>
<-[FBSSerialQueue _performNext]+192>
<-[FBSSerialQueue _performNextFromRunLoopSource]+45>
<__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__+17>
<__CFRunLoopDoSources0+556>
<__CFRunLoopRun+867>
<CFRunLoopRunSpecific+488>
<-[UIApplication _run]+402>
<UIApplicationMain+171>
<main+117>






Aug  7 14:27:00  <Error>: CGContextTranslateCTM: invalid context 0x0. Backtrace:
<-[UIStatusBarItemView updateContentsAndWidth]+33>
<-[UIStatusBarItemView initWithItem:data:actions:style:]+477>
<+[UIStatusBarItemView createViewForItem:withData:actions:foregroundStyle:]+134>
<-[UIStatusBarLayoutManager _createViewForItem:withData:actions:]+163>
<-[UIStatusBarLayoutManager _prepareEnabledItemType:withEnabledItems:withData:actions:itemAppearing:itemDisappearing:]+36
<-[UIStatusBarLayoutManager prepareEnabledItems:withData:actions:]+92>
<-[UIStatusBarForegroundView _setStatusBarData:actions:animated:]+797>
<-[UIStatusBarForegroundView setStatusBarData:actions:animated:]+332>
<__51-[UIStatusBar _prepareToSetStyle:animation:forced:]_block_invoke+360>
<+[UIView(Animation) performWithoutAnimation:]+65>
<-[UIStatusBar _prepareToSetStyle:animation:forced:]+866>
<-[UIStatusBar _requestStyleAttributes:animationParameters:forced:]+391>
<-[UIStatusBar requestStyle:animationParameters:forced:]+437>
<-[UIStatusBar requestStyle:animated:forced:]+90>
<-[UIStatusBar _evaluateServerRegistration]+250>
<__45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke+590>
<-[UIView(Hierarchy) _postMovedFromSuperview:]+544>
<-[UIView(Internal) _addSubview:positioned:relativeTo:]+1967>
<-[UIStatusBarWindow setStatusBar:]+288>
<-[UIApplication _createStatusBarWithRequestedStyle:orientation:hidden:]+340>
<-[UIApplication _runWithMainScene:transitionContext:completion:]+950>
<-[UIApplication workspaceDidEndTransaction:]+188>
<-[FBSSerialQueue _performNext]+192>
<-[FBSSerialQueue _performNextFromRunLoopSource]+45>
<__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__+17>
<__CFRunLoopDoSources0+556>
<__CFRunLoopRun+867>
<CFRunLoopRunSpecific+488>
<-[UIApplication _run]+402>
<UIApplicationMain+171>
<main+117>








Aug  7 14:27:00 <Error>: CGContextRestoreGState: invalid context 0x0. Backtrace:
<-[UIStatusBarItemView updateContentsAndWidth]+33>
<-[UIStatusBarItemView initWithItem:data:actions:style:]+477>
<+[UIStatusBarItemView createViewForItem:withData:actions:foregroundStyle:]+134>
<-[UIStatusBarLayoutManager _createViewForItem:withData:actions:]+163>
<-[UIStatusBarLayoutManager _prepareEnabledItemType:withEnabledItems:withData:actions:itemAppearing:itemDisappearing:]+36
<-[UIStatusBarLayoutManager prepareEnabledItems:withData:actions:]+92>
<-[UIStatusBarForegroundView _setStatusBarData:actions:animated:]+797>
<-[UIStatusBarForegroundView setStatusBarData:actions:animated:]+332>
<__51-[UIStatusBar _prepareToSetStyle:animation:forced:]_block_invoke+360>
<+[UIView(Animation) performWithoutAnimation:]+65>
<-[UIStatusBar _prepareToSetStyle:animation:forced:]+866>
<-[UIStatusBar _requestStyleAttributes:animationParameters:forced:]+391>
<-[UIStatusBar requestStyle:animationParameters:forced:]+437>
<-[UIStatusBar requestStyle:animated:forced:]+90>
<-[UIStatusBar _evaluateServerRegistration]+250>
<__45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke+590>
<-[UIView(Hierarchy) _postMovedFromSuperview:]+544>
<-[UIView(Internal) _addSubview:positioned:relativeTo:]+1967>
<-[UIStatusBarWindow setStatusBar:]+288>
<-[UIApplication _createStatusBarWithRequestedStyle:orientation:hidden:]+340>
<-[UIApplication _runWithMainScene:transitionContext:completion:]+950>
<-[UIApplication workspaceDidEndTransaction:]+188>
<-[FBSSerialQueue _performNext]+192>
<-[FBSSerialQueue _performNextFromRunLoopSource]+45>
<__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__+17>
<__CFRunLoopDoSources0+556>
<__CFRunLoopRun+867>
<CFRunLoopRunSpecific+488>
<-[UIApplication _run]+402>
<UIApplicationMain+171>
<main+117>