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Tracking Fingers

I decided to spend the evening writing on a new type of iPad game controlling class I came up with the other day. Even though I didn’t plan to use more than one touch point I started out playing with some multitouch code. I wanted to see if I could continuously track a bunch of touch points at once without mixing them up.

It all went all right at first but suddenly I noticed that some of the tracking nodes wasn’t removed even though the tracked touch were. After some tests I realised that I didn’t always got notified when a touch ended. We can’t have that!!! After even more tests I gave up trying to solve the matter using the standard callback methods touchesEnded and touchesCanceled, I just couldn’t trust them anymore. :-(

The solution was to keep track of the active UITouch objects and then check the phase property. Since the UITouch object is the same instance through out the complete touch-lifecycle I only had to store them in a separate dictionary and check them every now and then.

Want to see how I did it? Download the Xcode project below. :-)

FingerTracker.zip

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