I have a UICollectionView as the top view on my view hierarchy in IB. It's making use of a custom layout that splits the cells (registered from nibs) along the left and right edges of the view, with decoration views behind and a supplementary view the size of the entire view on top of the cells. All of that works as expected.
What doesn't work is that selecting cells is simply not being registered. They're not firing calls to collectionView: didSelectItemAtIndexPath: (the delegate is set correctly), nor is the highlighted state of the images within the nib working. It's acting rather like a view higher up is consuming the tap, but the collectionView is the top view. I've tried removing the overlaid supplementary view and background decoration views, and also tried temporarily converting to using a flow layout in case my custom layout was doing something screwy - still nothing. Making this even more frustrating is the fact I'm using collectionViews on other view controllers in this app (governed by flow layouts), and they work perfectly fine without any special customisation. I'm out of options, any ideas?
Problem solved. Turned out the nib I was using had a single view that was, for some reason, an instance of UICollectionReusableView, not UICollectionViewCell. Presumably, the reusable view class is designed to not allow selection by default.
Related
I seem to be having a very strange problem with my UITableview cells and autolayout. So my tableview is set up as follows:
I have a UITableView within a UIViewController that I created via Interface builder using Autolayout
My tableview is using UITableViewAutomaticDimension so that the cells can resize based on the text within them.
Each cell has 2 subviews within it. A front view and a back view. The back view contains the buttons for my slide-able cells
I am using NSFetchedResults controller to update the tableview
The problem occurs when I tap on a cell and am taken to the next view. Then I create a core data item within that view and save so that it is inserted into my tableview (now behind the current view controller).
What happens is that the newly inserted cell seems to lose all autolayout constraints and all view elements are on top of each other in the top left of the cell. It also looks like they are not even contained within the front view for the cell (or the front view has a width and height of 0).
Example:
It gets even stranger. If I refresh the tableview by pulling down and the cells are reloaded it corrects itself. However, if I refresh the tableview again then the problem appears again but on a different cell. This bug does not happen consistantly which is rather frustrating.
Any help would be appreciated as I only have a few remaining hairs on my head to pull out at this stage.
Thanks in advance!
So I found out what the issue was. The issue was that I was using size classes in Interface builder but I was only using the iPhone Portrait size class and did all my work in there instead of the "any" size class. Disabling size classes and setting the project to iPhone only fixed all these problems.
Weird I know
I need to have iOS app with screen like this:
screen
The idea is when user start to scroll down the first UIView to move up until the second UIView reach the top where it will stick and only UICollectionView will continue to move up.
Currently I'm using this structure
UIScrollView (main scroll)
UIView (some banners)
UIView (UISegmentedControl)
UICollectionView (grid with items, scroll is disabled, main scroll is used)
I manage to do it, but I needed to set UICollectionView height constraint manually in the code (calculated based on all items in grid) in order to appear in UIScrollView (everything else is handled by AutoLayout in Storyboard). The problem with this is that UICollectionView think all cells are visible and load them, so the whole recycling & reusing thing does not work. It's even worst because I use willDisplayCell method on UICollectionView to load more data when last cell is displayed, but now it load all pages at once.
My question (actually they are 2)
How can I fix the issue above?
What is the right way to achieve this functionality? Maybe my whole approach is conceptually wrong?
Collection view is a scroll view itself. So maybe you could have same functionality only with Collection view with sections or even custom layout?
I have a gallery using UICollectionView that prepared using main.storyboard. I have a few UIViews and UIButton placed between UICollectionView and UICollectionViewCell. When I test the app, some of the UIViews and UIButtons disappear.
But I have another catalog scene which prepared using the same way and everything is there. What seems to be the issue?
I wouldn't mess with the UICollectionView's view hierarchy this way. Since it handles its own list of subviews, yours may be obstructed. I would suggest one of those two methods:
Set your UICollectionView background as [UIColor clearColor], and put your own views behind that UICollectionView, in a hierarchy similar to this:
UIView
Your Custom Views
UICollectionView
Use the UICollectionView's decoration views. You can read more about them here, in the "Including Decoration Views in Your Custom Layouts" section.
Decoration views are visual adornments that enhance the appearance of
your collection view layouts. Unlike cells and supplementary views,
decoration views provide visual content only and are thus independent
of the data source. You can use them to provide custom backgrounds,
fill in the spaces around cells, or even obscure cells if you want.
Decoration views are defined and managed solely by the layout object
and do not interact with the collection view’s data source object.
I need to build a UICollectionView with a UICollectionViewFlowLayout and a very dynamic "header" (for clarity, I'll call it "view A" to avoid mixing it with a true collection view header) but I'm not sure about what can be the best way to do that: collectionViewCell, header or supplementary view?
What I mean by flexible, the bullet point being ordered by decreasing importance:
View A will contain buttons and subviews that need to detect gestures so I must be able to detect actions on subviews of view A.
I need to be able to reload data on the collection view without reloading view A.
I need to be able to update the layout of subviews of view A whenever I want (on viewDidScroll of the collection view delegate for example, update according to contentOffset changes).
If possible, I'd like to be able to change the frame of view A dynamically (I mean without having to invalidate the layout). I would like view A to be sticky at the top and shrink while scrolling until it disappear. Have a look at recently launched "Secret" app to see what I mean (done on UITableView for them). Though I could just scroll without changing the frame and cheat by changing the layout of subviews (see point 3) in order to give the sensation of a sticky header.
What do you think is the best component to do that? Can I use a UICollectionViewCell, a header or a supplementary view? If so which one? If not, do you think of an alternative way I could use to have the same behavior (transparent header and view A behind the collection view? adding view A somewhere else, where, in the view hierarchy?).
Thanks for your help!
Take a look at the UICollectionReusableView class.
You can register your nib on the CollectionView as "SupplementaryView" (registerNib:forSupplementaryViewOfKind:withReuseIdentifier:, use the UICollectionElementKindSectionHeader kind of view)
then you have to implement the collectionView:viewForSupplementaryElementOfKind:atIndexPath: method in your delegate and make sure to return something for the UICollectionElementKindSectionHeader kind.
and finally you have to implement the collectionView:layout:referenceSizeForHeaderInSection: method of your UICollectionViewDelegateFlowLayout to set the size of your header.
Let me know if it help.
I'm starting my development of an ios app using ios 6 and UICollectionView.
I've noticed there's support for both supplementary views and decoration views.
Can someone please explain in bullet points the difference between the two? They sound very similar.
If I want to add a loader to my collection view (that will appear at the bottom of each section, while the section is loading) should it be a supplementary view or a decoration view?
Thanks
Decoration views are just what the name says: decoration, chrome. Only the collection view layout decides what they are and where to put them (for instance, if you want to draw lines on the screen every 5 items).
Supplementary views are more related to your data. The collection view layout still decides where to put them, but they are provided by the collection view data source, just like regular cells. For instance, if you wanted to put titles for sections, you would use supplementary views because the title would be different for each section and you need to call the data source for each.
If your loader is generic, it could be a decoration view, however decorations views are not really accessible (the layout object says where to put them, and that is it, they are created by the collection view and you never get a reference to them), so if you want to start/stop animating it, a decoration view is not the best choice. If you use a supplementary view, then you have access to it at creation time (in your data source collectionView:viewForSupplementaryElementOfKind:atIndexPath: method). However, you can only query the collection view for regular data cells once they are laid out on screen.
Also, you will have to write your own UICollectionViewLayout class if you want to use custom decoration or supplementary views. The base UICollectionViewFlowLayout only provides for a footer and a header supplementary view.
from UITableView perspective :
Supplementary = sections.
Decoration = tableFooterView tableHeaderView