Consider the following:
I have a UICollectionView with a size of 400x400. This UICollectionView has 5 UICollectionViewCells which also have a size of 400x400.
Clip to bounds is set to false so that my UICollectionViewCells will be visible (this does not work, I can only see 1). I want this so I can use paging. When I start scrolling there are 2 cells, but when the scrolling snaps, the previous cell disappears and I can only see 1 cell.
I use dequeueReusableCellWithReuseIdentifier to retrieve cells to fill the collectionview. Can this be part of the problem?
How can I display the UICollectViewCells that are out of the collection view's frame?
You can't. What you describe for a problem is actually a feature of UICollectionView and UITableView. They reuse the cells that are not visible for performance and memory reasons. You might think of another approach like UICollectionView with custom layout if that would be possible for your requirement or directly use UIScrollView with paging and you rearrange all the views while is scrolling.
Related
I have UITableViewController with 1 section and header with UISegmentedControl inside.
If user presses first segment we should display UITableView cells
If user presses second segment we should display custom vertical scrolling collection grid with collection items below that header
possible solutions:
change UITableViewController to UICollectionViewController, and UITableViewCells to UICollectionViewCells. This should work but I'm trying to avoid this solution
UICollectionView embedded in UITableViewCell. Setting UICollectionView scrolling enabled to false, adjusting UITableViewCell's height to fit entire UICollectionView's contentSize.height. In systemLayoutSizeFitting(...) method of container (UITableViewCell) we call layoutIfNeeded on container and on contained UICollectionView and return UICollectionView's contentSize.
problem:
(re)calculation of entire UICollectionView contentSize requires a lot of work if we have hundreds of items (cellForItemAtIndexPath for every item). Want to avoid this somehow. Maybe we can increase container (UITableViewCell) height during scrolling UICollectionView which is embedded inside.
Same as 2 but we have fixed size container UITableViewCell (same height as view without header) with UICollectionView inside. When we scroll UITableView to the very bottom UICollectionView scroll should continue scrolling.
problem:
I don't understand how to deal with 2 instances of UIScrollView with scrollingEnabled = true for both. I think this could be solved with pan gesture recognizer delegates. If it is so I need help here.
I would personally opt for number 1 and completely avoid number 2. For number 3, you could set tableView.scrollingEnabled = false when the second segment is tapped. Set it to true when the first segment is tapped. That way, when it's false, the UICollectionView in your UITableViewCell can still scroll.
This tutorial may help with putting a UICollectionView in a UITableViewCell.
I have a collection view. I need to scroll only cell4, cell5, cell 6 so on. First two cells are remain same. Is is possible using only UICollectionview. How to achieve this.
FYI: the height of the cell is more than the screen height.
One of options would be to subclass UICollectionViewLayout and update frames in attributes of first three cells every time when scroll offset changes. So the cells would look static.
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?
If you look at the Featured tab of the Apple App Store app on an iPhone 6, there is a unique UI layout that I can't figure out how to replicate.
At the very top there is a navigationBar. Below this there is a UIScrollView that animates through a number of featured items. Below this is what appears to be a UITableView with a number of custom programmed cells.
My first guess was that the UIScrollView at the top was added to a custom cell at the top of a UITableView. If you swipe up the UIScrollView moves with the objects below like it is a cell. You can see that the vertical scroll indicator starts at the top of the UIScrollView.
The part that is unique is that if you swipe down, the objects below the UIScrollView move down like a UITableView and the UIScrollView stays in place. This means that the UIScrollView is not a custom cell at the top of a UITableView.
I tried making this work a number of different ways but I can replicate this. Does anyone know how this can be done?
You can use a tableview header,the header is a scrollview
If you scroll tableview up,just use tableview default behavior,the header will scroll up.
If you scroll down,use UIScrollViewDelegate to calculate the tableview header new frame,and adjust it.So it remain at top
Not sure if I got you correctly, you may use UICollectionView as vertical scroll. Then, you create a custom UICollectionViewCell, each with horizontal scroll.
I haven't tried it though but done something similar to this. Hope you find a way!
I have a slightly complicated system that I am having some reuse issues with, wanted to get some feedback. Basically it is a vertical tableview, and each cell contains another tableview that is rotated 90 degrees, so that each cell scrolls horizontally. Each horizontal cell is also set up to scroll infinitely with paginated responses from an API. I am having issues where cells are copying on top of each other when the vertical table is scrolled down. I have reuse identifiers set up correctly and in each of the horizontal tableviews I am running the following:
- (void)prepareForReuse
{
[_horizontalTableView reloadData];
}
If I turn off reusing cells the issue doesn't happen, but the vertical scrolling performance suffers. I am wondering if its possible that reusing cells in this type of a set up just isnt possible? Any experience with this is helpful. Thanks.
This is not a direct way to solve your issue, but I believe if you use a horizontal scroll view inside each vertical cell, you will have this done faster and with less weird behaviours. I also believe this is not a standard way, so weird stuff will happen.
All you do is set or extend the content size of the scroll off screen continuously to create an infinite scrolling behaviour. Create views within the scroll view pragmatically to simulate each cell. Hope this helps.