ios - Jittery / laggy UI updates while dragging UIScrollView -

ios - Jittery / laggy UI updates while dragging UIScrollView -

i have uiscrollview utilize purely it's contentoffset. contentoffset changes, subview's moved around according simple math function. mostly, entails having y positions adjusted, not linearly respect uiscrollview's contentoffset.y.

an illustration of adjusting yposition this:

cgrect newframe = subview.frame; newframe.origin.y = log(scrollview.contentoffset.y) + 300; [subview setframe:newframe];

everything works fine in simulator , works great on device while uiscrollview isn't receiving touches (~24-30fps), while user touching screen , dragging, fps drops ~3-5fps. between dragging , not, there shouldn't difference, except in run loop, potentially. adjust that, i've tried in scrollviewdidscroll:

[self performselector:@selector(updatecards) onthread:[nsthread mainthread] withobject:nil waituntildone:yes modes:@[nsrunloopcommonmodes, uitrackingrunloopmode]];

and variations, no effect.

is there reason fps drop off , there can prepare issue? using ipod 5th generation of these tests.

ios objective-c uiscrollview drag nsrunloop