Why is my touch event frequency slower on iOS 4.0?

I'm writing a finger sketch type app and had t开发者_C百科he app working great on iOS 3.0. However, running the app under iOS 4.0 or greater is causing problems. Specifically, I am receiving touch events to my app approximately 5x slower on the new OS than on the old. This obviously causes my app to draw poorly because I'm capturing 5x less data points to draw between.

Any ideas on how to speed up touch event frequency on iOS4?

Certain graphics operations take a lot longer in iOS4.x than in 3.x (somewhere between 2X to 10X slower). The longer graphics execution times could be blocking the main UI thread, and not leaving enough time for the main thread run loop to handle user (touch) events.

Profile your drawRect code and see if it's now taking longer that one refresh rate tick time. If so, try speeding up or breaking up your graphics renders, or try a lower frame rate, and see if any of that helps.

You should profile your code with Shark to see where the bottleneck is. What is probably happening is some of your code that executes on the main thread (most likely something that runs in response to a touch) is taking longer than expected which is preventing your app from receiving touch events

Block the main thread less.