Dim iPhone screen

I'm working on an application where it may be used in a dark area and th开发者_如何学JAVAe brightness is required to be lowered. I wanted to put this into the application, and thought that I could add a UIView with a black bg color and change the alpha, but this gets in the way of the user interaction.

Does anyone have an idea on how to do this without blocking human interaction?

Thanks

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Set the UIView's userInteractionEnabled property to NO.