I am using an UICollectionView to display a list of items in a 2 column layout with equal size of columns. This is obtained by a flow-layout.
Simple.
However, the first row is different from the rest, as it can vary from being full "screen" width or two column width. In continuation hereof, the collection view displays two types of cells (A and B). A is always displayed with full "screen" width in first row and B cells always in columns of two.
An option button can switch displaying type A cell or not.
All this can be brought to work with a flow-layout and proper width sizing of the items through delegates.
Unfortunately, when switching between not displaying type A cell with full width and displaying type A cell, an visual disturbance occur, because the collection view calls first delegate with "sizeForItem" and then collection view calls delegate "cellForItem":
collectionView(_:layout:sizeForItemAt:)
collectionView(_:cellForItemAt:)
This means that the "old" B cell in first row is being displayed with full width for about 1 second or less. Which does not look good.
Difficult to see any solution to this.
Hope someone can.
Below, three images shows how cell B is temporarily being shown with full width before cell A is being shown.
Related
Inside my UITableView I have 2 types of cells lets say A and B.
Initially, my table shows only cells of type A and when the user taps on any cell, I display a list of type B cells to give sort of a drop-down effect. Now the issue is when I tap on a cell of type A it's drop-down may have a large number of type B cells, so what I want to do is limit the number of cells in the dropdown to 3 and then scroll the rest of them in the same position and then have the list of type A cells after that. I have no idea how to do this, any help is greatly appreciated.
Try to set bellow constraint in your internal tableview that is collapse and expand.
A question for the UICollectionView experts.
Imagine a collection view that looks like a table view (full width cells), and when you tap on one of them, new cells are inserted underneath that cell that are square cells, say half the width of the collection view, in 2 columns. Tapping the header again would appear to collapse the section.
Keeping in mind that I’m trying to use UICollectionViewFlowLayout instead of a custom UICollectionView.
Would you:
A) implement the tableview style cells as collection view supplementary views (headers), with a gesture recogniser that inserts the square cells?; or
B) implement the tableview style cells as one cell type, and the square cells as another cell type?; or
C) something else?
Personally I would go with option A. In the situation you're describing the full width item is really a section header that's function is to show/hide it's sections's cells.
From a data structure standpoint this is much easier to maintain with this approach. It can be handled with an array of arrays.
If they were all cells it would most likely be one large array, and would be more difficult to make the distinction between a full width cell and the half width cells.
I have a collection view 3x3.
Item (collection cell) contains some icon and label.
I want some additional text to be shown inplace when user touches the cell. The view with this text must be fullscreen width.
In other words I want to insert a view with text between collection rows. It's desirable that the view appears with animation.
How should I do that? The first ideas I've got are:
Divide CollectionView rows into sections and use section footer for this purpose. Make this footer of zero size and show it when needed.
Dynamically create full-width cell and insert it at the end of the row where selected item is located.
Both methods seems tricky to me. Maybe there is more straight forward way?
Any ideas? Thanks!
Context:
Building an app that populates a table that takes in data from a asyc json dump.
The cells are of a custom class (I defined). The main label in the cell can be very long.
It is "placed" in storyboard within a prototype cell but customized via code (pretty standard stuff).
Labels are resized in cellForRowAtIndexPath and rows are resized via heightForRowAtIndexPath -- rows are resized by forcing a call to cellForRowAtIndex like Massimo's answer here
So per the question at hand - I've noticed some interesting (bad) things that happen.
First issue: When the table loads, the rows and labels are dynamically resized correctly! Great! However, when I scroll down and then scroll back up, the label heights will be incorrect -- (for example) the first row was correct at loading. Then when I scroll down and then scroll back up to see it again, it will be truncated. Specifically, the row size will be fine but the label height will change and become truncated to 2 lines only. Wondering if this is because I did both storyboard and coding to customize the cell. Anybody see this before?
Second issue: When I scroll down, while the rows are sized correctly (large), the labels are short (truncated.) Wondering if it's some reverse of the above "potential answer".
"potential answer" is that the rows are all calculated and stored "up front" so that scrolling down/then back up doesn't affect it. However, when cells go "out of view" and are dequeued then when they re-viewed (scroll down/then back up) it will rely on the storyboard.(inappropriately?)
All three of your issues are symptomatic of returning the wrong height in heightForRowAtIndexPath. In my data model classes I have a calculateHeight method that I call in heightForRowAtIndexPath. The model also caches the answer so it doesn't have to recalculate it after the first call. The cell class uses the model's calculated height to layout its subviews.
"ANSWERED" by deleting the prototype cell from the storyboard and making them fully in code, the issue went away. The fundamental workings are still not understood (ie. the interactions between storyboard vs. code when cells are put queued and then viewed again)
I have a tableview that has a large number of fairly tall dynamic cells. I've tried creating the prototypes for these but I've run out of height room in the view.
I can't seem to extend the height of the table view, (or the view it's in). I also can't create the tableview outside the viewController, give it a larger height, and just link to it.
Suggestions? I know I can create the cells programmatically or from a separate nib, but I'd really like to do it via storyboard.
thanks,
Just figured this out myself. Try this:
Double-click the table almost anywhere except where there's an existing control. You can also double-click on the outer edge of the table.
Note that the table view will show a highlighted section that aligns with the cell you've clicked. You've entered some sort of selection mode.
Now use the mouse to scroll up or down. The cells will shift up or down as if you were running the app.