如何设置CG_上下文_显示_回溯环境变量？

Question

我的视图中有三个按钮。在viewDidLoad（）中设置角Radus后：button.layer.cornerRadius=20我在日志中收到以下错误消息：

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

问题：

好吧，我现在从消息中找到了回溯。这对我没有任何意义。请帮帮忙...

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>

Answer 1

这个问题发生在Xcode 7上。在我的例子中，我从Info中删除了UIViewControllerBasedStatusBarAppearance。plist问题解决了！请参阅本文中的答案：

Answer 2

是9b5中的bug：
https://forums.developer.apple.com/thread/13683

向Apple提交RADAR。

Answer 3

您可以通过以下菜单设置环境变量：Product-