iOS 7 UIImagePicker preview black screen

Question

When i try to load camera from my code, camera preview is black. If I wait for 10-20 seconds it will show real camera preview. I found several questions and some of them sug

Answer 1

Had this myself - it happens if something is running on the main dispatch thread - are you resizing images by any chance?

It puts the preview onto the main thread and if something is using it, you get a black screen. It's a bug and the workaround is to either take over the main thread or to disable the photo picker until the queue is free