I am trying to achieve a newsstand like effect with a scrolling and repeating background. I could do this using a UITableView if I could set it's content size (An inherited method that seems to be overridden by something else in the UITableView Code) in order to fill the view with unscrollable cells.
Currently I am planning to make a custom uiscrollview. Which will be more complex and won't have the cell reuse.
So, is there a way to set a UITableView's content size.
You could semi-hack a 'contentSize' kind of control over a UITableView by simply setting the number of cells that you have (let's assume you have a 1 section table view and aren't using a 'grouped' styled table) to:
your desired height contentSize height / height for each cell (default is 44)
Now, your problem is that if you only have, say, three rows' worth of data to display, what to do with the rest of the cells? Well, simply set their backgroundColor to the same as the table's background color and their selectionStyle property to UITableViewCellSelectionStyleNone. Wham, now you have invisible cells, and can set the 'contentSize' of the table.
Note that your contentSize will only have a resolution of the height of your cells, if you leave the cell heights at their default 44, then you can only set the contentSize to a multiple of 44.
Related
I'm working on an iOS App right now and I want to build a view controller that uses a UITableView to create new events in a calendar (very similarly to how iOS handles event creation in the system calendar, actually). The table view has two sections, the first section holding a date picker and the second section holding two custom cells for entering an event name and notes via a text field and a text view. After playing around with them I managed to force-set them to the right size, but in the process I realized that I don't actually understand how iOS calculates individual cell heights, especially in a table view with multiple sections and multiple custom cell classes. So far, I've found a number of things that seem to play a role:
Contents of a cell, e.g. a text field and its constraints
Hugging priority and compression resistance priority of a cells content
Settings for row height and view height in the size inspector of the cell itself:
Arrangement and Autolayout settings in the size inspector of the cell
Settings for the rowHeight and estimatedRowHeight properties of a UITableViewController
The more I look into it, the more complex and confusing it all gets. Maybe one of you can shed some light on this shady bit of Swift magic?
Basically, the rule is that if the table view's rowHeight is UITableView.automaticDimension, then as long as the estimatedRowHeight isn't 0, you'll get automatic row heights, meaning that the height is determined by the cell's autolayout constraints from the inside out.
The settings can be made in respect to the table view as a whole (in code or in the storyboard) or for a single cell using the height delegate method.
Add your constraints in the cell in right way.
don't use tableview "height for cell" delegate method.
use this in your viewDidLoad
self.tableView.estimatedRowHeight = 44.0
self.tableView.rowHeight = UITableView.automaticDimension
I would say that table view has a bit tricky.
Originally it needed to know size of cell before the cell was created.
The height of cell is defined by UITableViewDelegate optional function tableView(_:heightForRowAt:)
If this function is not defined (or delegate is set to nil) then it will take value of tableView.rowHeight
For performance reasons there was also added tableView(_:estimatedHeightForRowAt:) and tableView.estimatedRowHeight
The idea was not to calculate height of every cell during fast scrolling (such calculation may be costly) and use height that is good enough.
So that are the basics before constraints layout.
Then magic came. You can return UITableView.automaticDimension as height (by delegate method or by setting tableView.rowHeight). It will force tableView to calculate height from cells' constraints (note that constraints must define that height so very likely you want to set content hugging and resistance priority of every label, and you will encounter 'errors' in storyboard/xib).
Since that operation is costly you Apple forces you to specify estimated height by yourself. Also it's important to set that value to something that makes sense, otherwise things like programatically scroll won't work correctly.
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.
I'm working on an app that will populate the tableview based on a web service response. So far the two content types I know I will be getting will be data shown in a textview, and also in a collection view. I've begun implementing Ash Furrow's AFCollectionView. The dynamic sizing for text areas is working, however the collection view is scrolling within a cell height that is even less than my estimatedRowHeight (210.0).
Because the collection view table cell is not correctly resizing is it possible to explicitly set the height for the collectionView cell(s), and let any of the text based cells remain dynamic?
Your self sizing cells use auto-layout to determine what height to be, and that's based on the intrinsic content size of the subviews. But, that's not the only way auto-layout can specify the height of a view. You can add a static height constraint to your cells which contain a collection view.
I'm trying to add a UICollectionView to my view to use as a scrolling date picker on a single line. I'd like this to be relatively compact, but I'm having trouble when setting the collection view's height in IB.
Basically if I drop the height of the frame below 114, my prototype cells disappear, and no cells are displayed when I run the app. As long as it's above that value, everything works fine.
I've also got a black bar of empty background space above the cells despite setting their height to the same as the frame's height in sizeForItemAtIndexPath.
My delegate and datasource are set up correctly, and my cell has an identifier set and is being dequeued just fine, as long as the view's height is large enough. Do I need to subclass UICollectionViewLayout to get a really short view to work?
Uncheck Adjusts Scroll View Insets on your view controller or set automaticallyAdjustsScrollViewInsets property on the view controller to false programmatically.
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.