I have UICollectionView in my custom keyboard, and it has two rows of cells with same heights, but different widths (size comes from server), direction of scroll is horizontal.
How can I show collection items side by side, without this strange centering which based on the previous cell width?
I've achivied needed result with SKRaggyCollectionViewLayout
P.S. If you'll use SKRaggyCollectionViewLayout, don't forget to put
self.layout.variableFrontierHeight = NO; to have same heights for all cells.
Related
I want to have self sizing cells within a tableview with self sizing cells. But on first initialisation some cells are not correct. After a scroll to the bottom and the cells will display again the cell size is correct. In the screenshot you can see that the top 2 cells have a white space at the bottom and the third one doesn't. They should all look like the third one.
This is the issue in my main project.
Screenshot
The problem with automatically sizing cells inside automatically sized cells is a bit tricky because you have to understand how it works. UITableView works with estimates most of the time. It usually does not calculate the contentSize precisely because to calculate it precisely, it has to first instantiate every cell, layout it and then calculate its size.
The precise values are calculated only for cells that are displayed (visible in current scroll frame).
The tricky part is that the inner cells (inside your outer cell) are not displayed until the outer cell is displayed therefore the outer cell does not have size calculated correctly. Also note that UITableView does not automatically update cell heights unless explicitly said to do so.
The solution, if you really have to do this, is to calculate the height of the outer cell correctly before it is displayed and manually set a height constraint.
If you know the height (from data source), it's easy. If you actually need to calculate the height of the inner table, you can do something like this:
// make the table high enough to display all cells
innerTableHeightConstraint.constant = 2000
// reload table
innerTable.reloadData()
// force layout
innerTable.layoutIfNeeded()
// now the contentSize is correctly calculated
innerTableHeightConstraint.constant = innerTable.contentSize.height
The whole concept is tricky and ideally you should prefer using UICollectionView or table sections. When you are using inner table views, there won't be any cell reuse for the inner tables and your performance will suffer.
You should not wrap UITableView into UITableViewCell, try to use UITableView Sections instead to add an extra depth level to your UITableView.
This illustration shows what i'm trying to do:
The green list is the UITableView where it dynamically adjust it's height based on the number of items inside of it.
Underneath of the UITableView is a button that should follow the UITableView whenever it changes it's height size.
The UIButton should always be beneath the UITableView whatever the size of the UItableView.
I'm currently using autoresizing for UITableView
I have tried to use Autolayout but it seems i can't still find the answer.
i currently have no constraints in the layout.
This boils down to calculating the height of the table view that perfectly fits the cells. Basically you need to measure the size of every cell, then create a height constraint on the table view, and set its constant to the sum of the cells' heights.
Measuring the height of cells is tricky thought. If you only have a few cells (like in your illustrations), you can just instantiate all of them, keep them in an array and use systemLayoutSizeFittingSize to calculate their sizes. If you use multi-line labels, it is also important to set their preferredMaxLayoutWidth to appropriate values.
However, if you have only a few cells (and so cell reuse is not important), stack view is probably a better choice than table view. It's just too tricky to calculate the perfect height of a table view.
First of all, I already read How to force UICollectionView with fewer items to scroll? and it did not solve my problem.
I have an horizontal UICollectionView with 5 cells, and only 5 cells are needed to fill the screen width. This means the 3rd cell is centered. How can I scroll so the 4th cell is centered?
When using scrollToItemAtIndexPath, it won't scroll since there is not enough cells to scroll. In other words, if I want my 4th cell to be centered, there would be a blank space at the end since I only have 5 cells (and vice-versa for the 2nd cell).
Is adding empty cells the only solution?
You could adjust the insets on the collection view. Add enough space that you can center the last cell.
More info from Apple
I have 3 labels in a UITableViewCell and have the labels set so they will wordwrap. If they word wrap the text goes into the next cell. How do I get AutoLayout to expand the cell based on the content without having to write code in the heightForRowAtIndex method? Isn't there a constraint I can use to automatically adjust the cell based on the contentView?
The cell looks fine if the text doesn't wrap in the label. Once it wraps that is when the problem occurs and I would like to have the cell resize to fit the content and have the same spacing between the bottom label and the bottom as there is between the top and top label.
Unfortunately no, you can't do this. A table view calculates its own total height first and has a fixed idea of the size of each cell as they load, it won't determine it's height from the outside in and it won't let layout constraints change the height of a cell.
If you think about how tables work, with cell reuse, then you couldn't really size the table from its cells without loading in every cell and adding it to the scrollview, and performing a layout pass on the whole thing. That would probably lead to quite poor performance.
You could experiment with populating a "free" cell (i.e a cell you've just instantiated, not added to a table) and laying it out for each row in your datasource when calculating heightForRow.
As you are loading the individual cells, after you fill the labels, but before you load the instance of the cell, check the label height.
Something like:
cell.frame.size.height
If the height is large enough that you know the label has wrapped to two lines, then increase the height of the cell you are about to load.
I made a UICollectionView with a vertical scroll.
The width of the cell is more than than the screen width, so I created a customFlowLayout based on UICollectionViewFlow layout returning the right calculated content size.
However, this doesn't work. When the width of the cell is less than the screen width it works. Does it mean that we can't have width more than than screen width in vertical scroll?
It is the same for horizontal scroll, but then the height of the CollectionView is limited to screen height.
Is there any way to make it work?
As others have already said, the UICollectionView can only scroll one direction using a flow layout. However you can accomplish this very easily without creating a custom layout or using a third party library.
When you lay your view out in story board, you can put your UICollectionView embedded in a UIScrollView. Have the scrollview set up to scroll horizontally and the UICollectionView to scroll Vertically. Then set the UICollectionView.delaysContentTouchesto true so touches will pass through to the UIScrollView and not think you are trying to scroll the collectionview.
When you set up the UICollectionView, set it's size and the size of the cells to be what you actually want them to be (Wider than the actual screen) and lay them out accordingly.
Now in the containing UIViewController put this code in the view lifecycle
- (void)viewDidLayoutSubviews {
self.myScrollView.contentSize = self.myCollectionView.frame.size;
}
That's literally all you have to do to accomplish what you are describing. Now your scrollview should allow you to scroll horizontally to view your entire cell and your collectionView should scroll vertically through your cells.
Happy programming.
I'm not sure I've understood your problem.
But if you have made a custom layout, make sure you have implemented :
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath;
and that your layout attributes frame and size are set with correct values for your "large cell" index path.
Also make sure you have implemented :
- (CGSize) collectionViewContentSize;
This method returns the contentSize of the collection View. If contentSize.width > youAppFrame.width you should have horizontal scrolling. Same for height and vertical scrolling.
Also make sure your collectionView allows scrolling and that your layout is prepared correctly using :
- (void)prepareLayout
By the way, for your layout have you overloaded UICollectionViewLayout or UICollectionViewFlowLayout ?
Before you can do that you MUST use a different type of layout. The flow layout represents its items as a list and it spans these items in cells based on the available width.
If you want to have both horizontal and vertical scrolling you need to somehow specify the number of columns for your grid. the FlowLayout doesn't have that. A simple sollution is to make a subclass of UICollectionViewLayout and override collectionViewContentSize to make it retun a width = to the added sum of the cells widths of one row (this is where knowing how many collumns you want is necessary), plus any additional spacing between them. This will work fine if your cells have the same size per column, similar to a grid.
You should embed a UITableView into a UIScrollView.
ScrollView and TableView will have the same height but different widths.
This way UITableView will scroll vertical and UIScrollView will scroll horizontal.
Xcode 11+, Swift 5.
I solved my issue, I prepared video and code