CGContextSaveGState: invalid context 0x0 (Xcode 7 GM)

This also happens for me on 7 GM, but removing UIViewControllerBasedStatusBarAppearance from Info.plist fixed it for me, as said here.

Hi, I don't know what you mean exactly by 'white', but removing UIViewControllerBasedStatusBarAppearance means that the appearance of the status bar is now determined from the visible view controller, you have to implement preferredStatusBarStyle there and return the desired value. Note that if your content view controller is embedded in an navigation/tab controller, you have to implement it in the latter.

当前controller的 preferredStatusBarStyle方法返回no