CODEWITHSUNDEEP
iosuitableview
rfj001
rfj001

Reputation: 8498

Resizing UITableViewCell to fit Content Performance

I am trying to create a table to show posts by users with possibly variable lengths. I want each cell in my table to resize to fit the content of the UILabel containing the text of the post. Currently I am doing this with auto-layout, programmatically setting constraints and calculating the height of the table view cell based on the height of the UILabel. Everything looks as I want it to, except when rapidly scrolling through the table the performance is horrendous, with the CPU getting fully maxed out and unable to keep up with setting the constraints for each cell as they are reused and placed with new text.

I was wondering if anyone knows of a better way to do this. Is there a way I can continue to use auto layout to size my cells without sacrificing performance? Or would the best solution be to create different sized cells with different identifiers, and just choose the best fit based on the UILabel text size. I also read somewhere that UICollectionView has much better performance in displaying variable-sized content, would it be worthwhile/possible to try configuring a UICollectionView to display the messages, and somehow make it look like a UITableView?

Essentially I just need a suggestion on how to display messages of variable sizes (up to about 7 or 8 lines of text max) in a TableView-like manner without causing massive slowdowns as the user rapidly scrolls through the table.

Thank you

Upvotes: 0

Views: 174

Answers (2)

rfj001
rfj001

Reputation: 8498

The way I had implemented adding the constraints, the constraints were updated whenever [self updateViewConstraints] was called, regardless of whether or not the cell had already had its constraints calculated and applied. I resolved this by adding a BOOL property to my custom TableViewCell called didUpdateConstraints, and setting it to YES as soon as constraints are updated the first time. Then in my [self updateViewConstraints] method I only update the constraints if !self.didUpdateConstraints

Now that constraints are not being needlessly updated when all views have already been correctly constrained, the performance is significantly better, and I don't observe any slowdown upon scrolling through the table.

Upvotes: 0

danh
danh

Reputation: 62676

The best trick in the book for things like this is cacheing. Add to your model anything that's expensive to compute (not the views themselves, but the computational results, like view bounds sizes). Make your datasource methods all about looking up and assigning, not at all about computing.

Upvotes: 1

Related Questions