]
07-21-2023, 02:28 PM
In iOS 8 the `UICollectionViewFlowLayout` supports automatically resizing cells based on their own content size. This resizes the cells in both width and height according to their content.
**Is it possible to specify a fixed value for the width (or height) of all the cells and allow the other dimensions to resize?**
For a simple example consider a multi-line label in a cell with constraints positioning it to the sides of the cell. The multi-line label could be resized different ways to accommodate the text. The cell should fill the width of the collection view and adjust it's height accordingly. Instead, the cells are sized haphazardly and it even causes a crash when the cell size is larger than the non-scrollable dimension of the collection view.
---
iOS 8 introduces the method `systemLayoutSizeFittingSize: withHorizontalFittingPriority: verticalFittingPriority:` For each cell in the collection view the layout calls this method on the cell, passing in the estimated size. What would make sense to me would be to override this method on the cell, pass in the size that is given and set the horizontal constraint to required and a low priority to the vertical constraint. This way the horizontal size is fixed to the value set in the layout and the vertical size can be flexible.
Something like this:
- (UICollectionViewLayoutAttributes *)preferredLayoutAttributesFittingAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes {
UICollectionViewLayoutAttributes *attributes = [super preferredLayoutAttributesFittingAttributes:layoutAttributes];
attributes.size = [self systemLayoutSizeFittingSize:layoutAttributes.size withHorizontalFittingPriority:UILayoutPriorityRequired verticalFittingPriority:UILayoutPriorityFittingSizeLevel];
return attributes;
}
The sizes given back by this method, however, are completely strange. The documentation on this method is very unclear to me and mentions using the constants `UILayoutFittingCompressedSize` `UILayoutFittingExpandedSize` which just represent a zero size and a pretty large one.
Is the `size` parameter of this method really just a way to pass in two constants? Is there no way to achieve the behavior I expect of getting the appropriate height for a given size?
---
## Alternate Solutions
1) Adding constraints that will be specify a specific width for the cell achieves the correct layout. This is a poor solution because that constraint should be set to the size of the cell's collection view which it has no safe reference to. The value for that constraint could be passed in when the cell is configured, but that also seems completely counterintuitive. This is also awkward because adding constraints directly to a cell or it's content view is causing many problems.
2) Use a table view. Table views work this way out of the box as cells have a fixed width, but this would not accommodate other situations like an iPad layout with fixed width cells in multiple columns.
**Is it possible to specify a fixed value for the width (or height) of all the cells and allow the other dimensions to resize?**
For a simple example consider a multi-line label in a cell with constraints positioning it to the sides of the cell. The multi-line label could be resized different ways to accommodate the text. The cell should fill the width of the collection view and adjust it's height accordingly. Instead, the cells are sized haphazardly and it even causes a crash when the cell size is larger than the non-scrollable dimension of the collection view.
---
iOS 8 introduces the method `systemLayoutSizeFittingSize: withHorizontalFittingPriority: verticalFittingPriority:` For each cell in the collection view the layout calls this method on the cell, passing in the estimated size. What would make sense to me would be to override this method on the cell, pass in the size that is given and set the horizontal constraint to required and a low priority to the vertical constraint. This way the horizontal size is fixed to the value set in the layout and the vertical size can be flexible.
Something like this:
- (UICollectionViewLayoutAttributes *)preferredLayoutAttributesFittingAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes {
UICollectionViewLayoutAttributes *attributes = [super preferredLayoutAttributesFittingAttributes:layoutAttributes];
attributes.size = [self systemLayoutSizeFittingSize:layoutAttributes.size withHorizontalFittingPriority:UILayoutPriorityRequired verticalFittingPriority:UILayoutPriorityFittingSizeLevel];
return attributes;
}
The sizes given back by this method, however, are completely strange. The documentation on this method is very unclear to me and mentions using the constants `UILayoutFittingCompressedSize` `UILayoutFittingExpandedSize` which just represent a zero size and a pretty large one.
Is the `size` parameter of this method really just a way to pass in two constants? Is there no way to achieve the behavior I expect of getting the appropriate height for a given size?
---
## Alternate Solutions
1) Adding constraints that will be specify a specific width for the cell achieves the correct layout. This is a poor solution because that constraint should be set to the size of the cell's collection view which it has no safe reference to. The value for that constraint could be passed in when the cell is configured, but that also seems completely counterintuitive. This is also awkward because adding constraints directly to a cell or it's content view is causing many problems.
2) Use a table view. Table views work this way out of the box as cells have a fixed width, but this would not accommodate other situations like an iPad layout with fixed width cells in multiple columns.