Understanding UIScrollView Constraints

Question

I have a UIScrollView with a UIView inside it and 3 UITableViews inside the view and I have the following constraints for the view :

In my code, exactly in ViewDidLayoutSubviews I have the following code

- (void)viewDidLayoutSubviews { [_containerScrollView setContentSize:CGSizeMake(SCREEN_WIDTH * 3, [_containerScrollView frame].size.height)]; [_contentViewWidthLayoutcontraint setConstant:SCREEN_WIDTH * 3]; [[self view] layoutIfNeeded]; }

Which change the view width realtivly to the screen width.

My question is why there is no conflict between the width constraint and the leading/trailing constraints ?

eric long · Accepted Answer · 2018-10-24 10:23:30Z

2

With your layout constraints, View's frame size is now become ScrollView's contentSize. So if you change _contentViewWidthLayoutcontraint's constant, it is same as you change ScrollView contentSize.width.

Note that ScrollView.frame.size and ScrollView.contentSize are totally different.

edited Oct 24, 2018 at 10:23

answered Oct 24, 2018 at 10:17

eric long

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3 Comments

OXXY Over a year ago

so you mean I can remove the first line in my code?, also I have a problem with width and leading/trailing constraints. Aren't they conflicted ?!

eric long Over a year ago

Yes, you can remove first line.

eric long Over a year ago

Width and lead/trailing may have conflict in some cases, like UIView.

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