Faking landscape orientation in Activity when locked in portrait

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http://stackoverflow.com – The camera app on Android locks its orientation to to portrait, and fakes an orientation change when you turn to landscape. The screen never re-orients itself (you don't see the screen reload or shift at all), but the icons turn to make it seem like it changed the orientation. How are they achieving this? Let's say I did this. So I'm locked in landscape mode, and I rotate the phone so I'm in portrait (at least that's what it looks like to the user). Now if I have any dialogs that pop up on this Activity, I'd want them to pop up in portrait orientation. How would I achieve this? (HowTos)