Shake event detection in all view controllers

Is this possible in iOS, or do I really have to register a shake event detection in every single view controller?

I want that a use开发者_运维知识库r of my app can shake his iPhone to return to the root. Regardless of the current view controller.

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I've done this by writing a category on UIViewController. This way you don't need to subclass anything, you can implement it even if the user interface has been finished already.

In my implementation, the VCs will respond to the shake unless the specific VC has opted out of the mechanism. Opting out is done by setting a BOOL ivar to NO in the specific implementation. The shake mechanism will look for this ivar using key-value-coding and ignore the shake if the ivar has been set.

I'd further refine this by allowing only the VC to respond which is currently visible.

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edited post (old information was wrong)

in your case I would write my own ViewController which subclasses UIViewController, implements the motion-delegates of UIResponder and will then call the popToRootViewController on the navigationController-property of the ViewController. And everytimes you create a new ViewController you should subclass your ViewCOntroller and not UIViewController. So every ViewController is able to receive the shake-event but it is only written once in your code :)

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This is just a guess, but maybe you could do it by subclassing UIApplication (not your app delegate, the actual application). UIApplication is a UIResponder, so you can make it the first responder, and provide a motionBegan or motionEnded method on it.