How to keep a UIView pointing in a certain direction regardless of device orientation?

Question

I have a UIView that I want to always be facing up. So say you have an UIImageView that has an arrow, and no matter what way the device is being held, it's pointing up. Obviously I need the accelerometer, but telling it to rotate the image based on the coordinates is only going to work the first time I think, since rotations are relative. Is there an easier way of doing this? I feel like there would be a simple example app somewhere that would do something like this.

Answer 1

Apple has sample code which does exactly what you want; have a look at this: http://developer.apple.com/library/ios/#samplecode/WhichWayIsUp/Introduction/Intro.html

To receive specific motion data, use the shared instance of UIAccelerometer and it's delegate. http://developer.apple.com/library/ios/documentation/UIKit/Reference/UIAccelerometerDelegate_Protocol/UIAccelerometerDelegate/UIAccelerometerDelegate.html#//apple_ref/occ/intf/UIAccelerometerDelegate

As far as the rotations, I'm not sure. Have a look at the "BubbleLevel" sample code here: http://developer.apple.com/library/ios/samplecode/BubbleLevel/Introduction/Intro.html#//apple_ref/doc/uid/DTS40007331

The accelerometer delegate documentation references that and other relevant sample code.