How to provoke a modal view popup by rotating the device to landscape?

I am working on an App where I want to show a modal view controller when the user rotates the de开发者_开发技巧vice. It should dismiss when the user rotates it back to portrait. During the rotation, the main view controller shouldn't be rotated.

How can I manage that?

I tried putting the code into the shouldAutorotateToInterfaceOrientation: method for showing the modal view controller, but I got always an error.

Some ideas?

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In the appDelegate you could use

[[NSNotificationCenter defaultCenter] addObserver:self
                                        selector:@selector(didRotate:)
                                             name:UIDeviceOrientationDidChangeNotification
                                           object:nil];

and define the method

- (void) didRotate:(NSNotification *)notification

In this method, fetch the new orientation and apply or remove the modal view controller.

In shouldAutorotateToInterfaceOrientation: limit the original view to only accept the one orientation you want it to have.

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you need to put this code in the

-(void) willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration

method of your view controller. Basically you will set your shouldAutorotateToInterfaceOrientationMethod: to return TRUE for any orientations you want to support (including the modal view popup). and then in the first method listed you implement the modal view controller becoming active.