如何让superview适合自动布局的最大内在大小子视图

Question

I have a column of multiple dynamic subviews with intrinsic sizes (images, labels, etc). How can I have the superview fit the subviews in autolayout.

If the subviews were not dynamic, I would just constrain the largest subview's leading/trailing edge to the superview. Like so

I thought I'd be able to align to the leading edge and then have the trailing constraints be >= 8 , the logic being "The trailing edge can be greater than 8 if the subview is too narrow, but if the subview is wide expand the superview so there's at least a trailing edge of 8." But IB does not like that

Caveats:

• Can't use stack view
• subviews have dynamic widths. So in the example any row could be the widest.

Answer 1

Okay here's how I got it working. Not sure if this is the best way.

1. Set all the trailing constraints to >=
2. Set a width on the superview
3. create an outlet for the superview width constraint
4. In your ViewController, override viewDidLayoutSubviews()
   1. Calculate the largest width out of all your subviews
   2. add your margins to that width
   3. set the superview width constant to the max that was calculated

Answer 2

Follow the below steps,

1. Add a view (say view A) to the main view.
2. Add all three labels (say label 1, label 2, label 3)to the view A as sub views.
3. Pin View A to its super view to all four sides. Change constraints at the top,bottom,left and right as greater than equal to (>=)10 where priority is set as required(because to avoid view A extending out of the screen if contents extend).
4. Add constraints to label 1, that is pin it to top,right and left of View A by constant is equal to 0. And pin bottom of label 1 to label 2 top is equal to 10 where constraint priority is set as required.
5. Follow same steps to label 2 as well.
6. Follow same steps to label 3. ie, pin it to bottom of label 2 and right, left of view A. Pin it to bottom of view A, where bottom constraint should be equal 0 where priority is set as low.

You can change constraints values based on your requirements. It will work. You can change the compression resistance priority to low whosoever label can shrink.

UPDATE:For the below mentioned git link

For ViewA add following constraints,

• ViewA center X and Y to SuperView center X and Y (=0 @1000)
• ViewA leading and SuperView leading (>=10 @1000)
• ViewA trailing and SupreView trailing (>=10 @1000)
• ViewA Top and SuperView Top (>=10 @1000)
• ViewA Bottom and Bottom trailing (>=10 @1000)
• Image1 to superview Leading,top (=0 @1000)
• Image1 to superview trailing (>=0 @1000)
• Image1 to Image2 Bottom (=10 @1000)
• Image2 to superview Leading (=0 @1000)
• Image2 to superview trailing (>=0 @1000)
• Image2 to Image3 Bottom (=10 @1000)
• Image3 to superview Leading (=0 @1000)
• Image3 to superview trailing (>=0 @1000)
• Image3 to superView Bottom (=0 @999)

Then select the ViewA and set update frames, there will be still red mark shown indicating Constraints are missing. Still you can add the missing Constraint what xcode suggests but set it to remove at build time . Update the frames and run. Hope it works as per your requirement.