vatti vatti - 16 days ago 4
iOS Question

Autolayout UICollectionView iOS 8

I have a UICollectionView added to a UIView. I just want the collection view to resize with orientation change, so that it fits the superview (UIView). After I add the layout constraint the collection view is missing. I could not even get the first constraint work properly.(below)

NSLayoutConstraint *leftSideConstraint = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:10.0];


And then I add the constraint to self.view.

What am I doing wrong? Please, help!

Update:
This is how it works. I am new to autolayouts. I was just trying to satisfy the constraints one by one to be sure that they all work:) Thank you

NSLayoutConstraint *constraint1 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:5.0];

NSLayoutConstraint *constraint2 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:-5.0];

NSLayoutConstraint *constraint3 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:-5.0];

NSLayoutConstraint *constraint4 = [NSLayoutConstraint constraintWithItem:self.collectionView
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:5.0];


[self.view addConstraints:@[constraint1, constraint2, constraint3, constraint4]];

Answer

You can't just add one constraint for view to position correctly. It needs to know it's x and y position, width and height. With this one constraint you only gave it x position. You need three more constraints eg. trailing, top and bottom or top, width, height. Basically any set of constraints that will fully describe view position, width and height.