Tracking progress of UIView animations?

[bdeshong]

I'm working on a game that is going to require knowing when one UIImageView and another intersect.

In a nutshell, the user is firing, let's say, bullets, while there is a timer used to launch targets onto the plane at random. When the "bullets" and the "targets" intersect, the "target" needs to explode.

To achieve this, I need to track the coordinates of each, but I'm finding that the CGPoint values for "center" aren't being updated as the animation progresses.

I could make a guesstimate on the progress based on the number of pixels being traveled with UIView, but that's really kind of a hack. Also, using the methods called when the animation is started and stopped doesn't really help me either.

I read elsewhere that only OpenGL will allow me to animate and track on a per-pixel basis. Does anyone know if this is the case, or can I somehow get by with the UIView animation functionality?

Thanks in advanced for any insight!

[scottiphone]

The built in animation functions are primarily where you want something to change from A to B and don't really care about the in-between points. This works well for things like the UI because you can just say do it and away it goes.

If you have a game or something where you need to really control the images directly the best thing is to do the animation yourself. Just change the frame position or transform. The redraw is handled automatically.

Setup an NSTimer and have it call you main animation routine. Since you're dealing with objects each can keep info specific to themselves. This isn't any different than OpenGL or other platforms. The advantage of OpenGL is where you have a number of still images moving around. At a certain point this is faster in OpenGL. The downside is you have to learn OpenGL as well and code for it.

[bdeshong]

Got it working great now, thanks! Handling the animation manually isn't too shabby...it's actually great to give me an understanding of how things work together.

Thanks again for the tip!