Profound UITableView rendering-performance problem, but only at certain positions?
Profound UITableView rendering-performance problem, but only at certain positions?
- Subject: Profound UITableView rendering-performance problem, but only at certain positions?
- From: Gavin Stokes <email@hidden>
- Date: Sun, 22 Jul 2012 21:45:06 -0700
I have a tableview that contains some graphic elements that rotate to
reflect the phone's heading. I only reload the visible rows, and I don't
do it while the table is scrolling. I filter the headings to 10-degree
increments to cut down the amount of heading updates I get.
Sometimes these work fine. But other times, the rendering is extremely
slow, with many overlapping images appearing before they're erased. Even
the labels in the cells are drawn offset and overlapping, although the
table's not in motion. In the video here, you can see numerous arrow
images being drawn before being erased. And in the middle of the third
second of video, note the cell image flying up from the bottom of the
screen and settling in the top row!
http://www.youtube.com/watch?v=wL2EYAro-oM&feature=youtu.be
Then if I scroll the table (keeping the same number of rows visible), the
problem often mysteriously disappears.
My theory is that the drawing performance suffers when the table is
scrolled to particular pixel offsets. So I'm logging the UITableView's
contentOffset, but that's always zero. Does anyone know how I can
determine how far the tableview is scrolled? Or does anyone have another
theory? I don't think there's a fundamental problem because again, the
updates work fine in some table positions.
Thanks!
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