iPhone draw with Core Graphics over an image

Question

Hello,

On my iPhone app, I would need to draw a kind of full gauge with a dynamic indicator. I was thinking of using a gauge image (a .png, that I would draw in an external tool) without any indicator, and then draw the dynamic indicator on top of the image. I was thinking of using a UIView with this image in background and then then use CoreGraphics (that I've never tried) to draw the indicator.

Do you think it's the easiest way to do this ?

thanks a lot,

Luc

Answer 1

I think you can't have a background image in the same view.

1°) You draw the image each time drawRect() is called
2°) You have two UIView, one who have the background image, and the other one which draw your gauge ;-)

Good Luck !

(I think the easiest method is the second one which don't re-draw the background each time :-))

Answer 2

Luc,

Your approach should work fine. Create a custom UIView and override -drawRect: to first draw the background PNG of the gauge, then draw the indicators.

- (void) drawRect: (CGRect) rect {
    \\ draw the gauge PNG into the view bounds
    ...;

    \\ Now use Quartz to draw the indicators
    ...; 
}