Question

Is there any way to measure scroll performance in an iPhone app, e.g. updates per second? I’m trying various techniques to improve the scrolling performance but it’s sometimes hard to judge if they’re actually having an effect.

Answer 1

if you have a scroll delegate, you can implement the method scrollViewDidScroll:. Specifically:

//header:
@interface MyClass : NSObject <UIScrollViewDelegate> {
    CFAbsoluteTime last;
    int updateCount;
    CFTimeInterval timeTotal;
}
@end

//implementation:
@implementation MyClass

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CFAbsoluteTime time = CFAbsoluteTimeGetCurrent();
    if (last > 0) {
        timeTotal += time - last;
        ++updateCount;
        if (timeTotal > 1) {
            NSLog(@"Updates Per Second: %.2f", updateCount / timeTotal);
            updateCount = 0;
            timeTotal = 0;
        }
    }
    last = time;
}

@end

Something like that. It’s untested, so the logging may be incorrect. But to use it, just assign your delegate to the scrollview.delegate property.