Hello,

This question is outside the scoop of the book, but i post it here cause it's one of my favorite forum on iphone development. I want to develop a gauge (like this on the image) with two buttons that increase and decrease the gauge. Can someone give me an idea on how to start this stuff? Thanks.

http://imageshack.us/photo/my-images...augeimage.png/

What part is holding you back? The animation/rotation?

You will need 2 UIImageViews, a background image and a overlay. The overlay will need to set its anchor point at the bottom of the image
overlay.layer.anchorpoint = CGPointMake(.5,1.0); //Uses unit coordinate system
http://developer.apple.com/library/m...es/Layers.html

Your action methods (button clicks) will increase or decrease your angle ivar which will apply to
overlay.transform = CGAffineTransformMakeRotation(yourIvar);

http://developer.apple.com/library/i...id/DTS40007434

May give you some ideas on how to deal with the animation.

I have done a simple version similar to your supplied image but using a speedometer. A slider is used to change the angle (speed to which the needle points), if you can't get what you need from these other references, I can make it available.

Bob

Thanks "thepianoguy" for this reply, ideas and links. I will try to do this using Core animation and your code is welcome . I was thinking about using : CGContext Class and it's methods like : CGContextAddArc and CGContextAddArcToPoint to build my arcs but i'm not sure!

Regards.

You plan to use the CGContextAddArc and CGContextAddArcToPoint for what? Drawing the background? A graphic image certainly seems simpler.

Bob

How can i use a graphic image? i need to animate the gauge value changes! is that wrong?

Thanks.

As I stated in my original reply, based on the image you posted, it appears that you need a background image which is static (empty - full) and an overlay image(foreground) which can animate, the needle that indicates the point between empty and full. The needle can be animated to rotate around its bottom point (anchorpoint). If you check out the link to the metronome project you can see how the graphics are animated in a different context but similar manner to this description.

Bob

Thanks man, i'm on the code of Metronome example, and i'll give you a feedback :).

Regards.

Thanks Bob for this great idea, really thanks, that's works just fine .

Kind regards.