AutoLayout constraints to UITableViewCell contentV

问题:

I'm trying to create dynamically resizing table view cells. I accomplished the resizing by using this answer, which is very detailed and helpful.

However, the maximum width for the label is not being calculated correctly inheightForRowAtIndexPath.

My cell currently only has one label in itscontentView, with constraints set to pin all the label edges to thecontentView edges. Here's what I have in IB

The cell size is being calculated with an offscreen cell inheightForRowAtIndexPath using

CGSize size = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];

During this process, it seems like it's honoring the constraints, and the label.preferredMaxLayoutWidth property is being set to 320, but when the label actually gets rendered, there is still padding.

回答1:

The paddings is layout margins. You have to be beware of Constrain to margins option.

Constrain to margins is Enabled:

Constrain to margins is Disabled:

How to disable it?

1. You can double-click the one of constrains and unchecking the Relative to margin option:

2. Unchecking the Constrain to margins while creating the constraints of the label:

Related link:
What is "Constrain to margin" in Storyboard in Xcode 6