NOTE: I added my new solution at the UPDATE answer below.
I try to recreate the effects we saw in Mobile Safari's tab on iPhone/iPod touch.
Basically, it's a UIScrollView that holds 4 reusable UIView (acting like ring buffer), and scrolls horizontally. When scrolling, the UIView's opacity will fade in/out seamlessly with offset.
Currently, I do all the dirty job in
- (void)scrollViewDidScroll:(UIScrollView *)scrollView. Such as getting the contentOffset from UIScrollView, determine the pageingation, calculate the delta between contentOffset and each UIView positions, and decide/set the alpha value of each UIView at the moment when
scrollViewDidScroll: was called.
And it works, performance is okay, everything runs smoothly, but the only problem is too much calculating.
I tried UIView's
commitAnimations:, but it's useless in
scrollViewDidScroll:, since 1) the new alpha value still have to be calculate by myself, and 2) scrollViewDidScroll: kept called when scrolling, it's meaningless to do the animation here. Is there any way to rewrite this part with Core Animation? So I don't have to do the math myself on alpha value of each UIView, instead, I can left whole works to Core Animation.