以编程方式拍摄屏幕快照时，UISegmentedControl中选定段的标题消失

我在UIToolbar中添加了UISegmentedControl:

UIToolbar *toolbar = [[UIToolbar alloc] initWithFrame:toolbarFrame];
toolbar.barStyle = UIBarStyleBlack;
toolbar.translucent = YES;
toolbar.barTintColor = [UIColor colorWithRed:0.97 green:0.97 blue:0.97 alpha:1.0];
[self.view addSubview:toolbar];

UISegmentedControl *segmentedControl = [[UISegmentedControl alloc] initWithItems:@[@"Last week", @"Last month", @"All time"];
[segmentedControl setSelectedSegmentIndex:0];
[toolbar addSubview:segmentedControl];

然后将工具栏添加到视图控制器.当我截取视图控制器的屏幕截图时，发生了一些奇怪的事情.所选段的标题消失.

The toolbar is then added to a view controller. When I take a screenshot of the view controller, something weird happens. The title of the selected segment disappears.

正在使用以下屏幕截图:

The screenshot is being taken using:

UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, YES, [[UIScreen mainScreen] scale]);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

渲染视图:

截屏:

从哪里开始寻找?