UITableViewCell Height Calculation and delegation?

I know this question had been asked hundreds of times before, but it's never really been solved (Or at least the way I'd like it to be). I have a rather complex UITableViewCell setup. The cell.backgroundView is loaded from a UIView subclass which uses a fair bit of CoreGraphics and CoreText. The code is rife with CTFramesetterSuggestFrameSizeWithConstraints, so I'm relectant to duplicate the class in the heightForRowAtIndexPath method.

I think I can solve this by creating an NSMutableDictionary with the indexPath as the key and the height as the value. But then I'm faced with the problem of heightForRowAtIndexPath being called first. I believe I can solve this problem by guessing the height of the cell and then once the cell's UIView subclass has finished rendering, use delegation to set the cell's height.

But this leaves me with the problem, how the hell do I delegate this? And, how to I prevent scrolling from being extremely choppy? as the cells will be created and resized in a split second.

Answers


In the past, I've used a dummy cell. I have a separate method -fillInCell:forRowAtIndexPath: which puts data into the cell. That way I can fill out the dummy cell in -tableView:heightForRowAtIndexPath: and the real cell in -tableView:cellForRowAtIndexPath:.

If this does not work for you then there are other options.

The first thing that comes to mind is create real cells in -tableView:heightForRowAtIndexPath: instead of -tableView:cellForRowAtIndexPath:. You can store completed cells in a mutable dictionary. -tableView:cellForRowAtIndexPath: will simply pull the completed cell from the dictionary. You should also detect when scrolling has stopped so you can empty your dictionary (just because -tableView:heightForRowAtIndexPath: was called doesn't mean -tableView:cellForRowAtIndexPath: will get call for the same indexPath).

Hope that helps.


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