Using UICollectionView with nested sections (stacking headers) - ios

I'm porting my web app to iOS using Swift 4, and I need to display a list which contains multiple nested "sections" where each section has its own header.
My instinct was to use UICollectionFlowLayout, but quickly discovered that it is limited to a depth of one. Diving further, figuring I would just have to create a custom layout, I see that the IOCollectionViewDataSource protocol actually assumes a depth of one.
I suspect I can find a way to flatten the data and reproduce the illusion of nested sections, but I'm baffled that I can't find an obvious way to have UICollectionView build what seems like a pretty common interface element. Perhaps I'm missing something?
Is there a common way for accomplishing this in UIKit?

Why not use a nested UICollectionView with your custom flowlayout, if you want UI like the way you shared in the question?
The idea would be,
UICollectionView (top)-> DataSource = [Headers: [dataSourceBelowTop]]
UICollectionView (inner) -> DataSource = dataSourceBelowTop
Take the example of the above case:
DataSourceTop is = ["Mission Gorge": ["Middle Earth": [SomeCustomModel]]]
The first task would be to build the top level UICollectionView, and then each collectionView will have another collection view. Now for Scrolling, you will need to play with the flowLayout which can be explained in another thread.

Related

How i can use multiple nib files with multiple arrays?

I am creating my iOS app, and i during that , now i have to build scrollable screen where there is image view, labels, collection view, Reviews etc (Prototype Image is attached). I am wondering is it possible to make that type of screen with UITable view using multiple Nib files? (If it is possible, kindly guide me as how i should use multiple Nib files with multiple arrays). And , if it is not possible, how else i can go for it? Kindly guide me, and sorry if thats a duplicate because i have searched but i was not able to find any good answer.
There are several approaches that you can do.
If you want to use UItableview, then you need to create multiple
UITableviewCells, where each cells is based on the section of the design. Then you can load it by using array, as you logic stated above. For example indexpath[0] you'll load the cell with the picture(lets call this pictureCell), then indexpath[1] you'll load descriptionCell, and so on.
The other approach is using Scrollview, with several UIViews on a vertical stackview. And then you'll create a UIView Subclass based on the section of the design. This is usually my go to solution.
I'm not sure what "array" is refering to here, but by the look of your screenshot, I would go with a StackView inside a UIScrollView, or something like that. No need for a UITableView if you don't have a repeting pattern, you can just stack multiple views in a scroll view.
I hope it's clear enough.

UITableView vs UICollectionView vs UIScrollView?

When should I use which, and what are the disadvantages or disadvantages of each? I'm mainly confused with scrollview vs collectionview, I know tableview is limited to one column (I heard it gets messy when more than one column), but scrollview difference with collectionview seem the same to me.
Both CollectionView & TableView are basically subclasses of UIScrollView.But as compared to UIScrollView here you are provided with proper methods to provide your dataSource & delegates to handle operations user performs on data. Along with this you are provided predefined layout classes.
Now to choose between them completely depends on your UI Requirements. Suppose you want to display just a list of items with a simple UI go with TableView.If you want a custom Layout like a grid or like the one you see in Apple's photo's app CollectionView is the choice.
if you have a complex UI & you have no idea about Custom CollectionView layout classes go with scrollView.
Consider UITableView and UICollectionView first and if you cannot achieve the effect you want with them, try UIScrollView then. UIScrollView is more basic class. UITableView and UICollectionView have more delegate method for us.
If you want a list,UITableView would be better. And if you want a multicolumn,use UICollectionView.

Implementing UICollectionView cell for items with variable number of subviews

Problem
I have a UICollectionView initialised from code and I register a custom class for its cells. The custom class has a few UIStackViews to lay out a bunch of UILabels and UIViews.
One of the arranged subviews should contain a variable number of UIViews. To make this less abstract, let’s think of them as “seats" that will display faces of users attending this event (can be up to four, can be none)
Solutions that come to mind
(I’m a novice)
Solution 1
Have the custom class lay out all the "seat" UIViews so I can treat them as placeholders;
Have the UICollectionView’s cellForItemAt method iterate over the data source and unhide the “seats” that have been filled
Solution 2
Make sure that the UIStackView in the custom class can be referenced from UICollectionView’s cellForItemAt method
From cellForItemAt use addArrangedSubview to add all the needed “seats”
Solution 3
Register 5 different classes (zero “seats” to “four seats”)
Dequeue each one as dictated by the data source
This one seems to me like the least dignified, but might be the one with least performance penalty
I'm perfectly aware that there could be more, and better, solutions. So, what would be the optimal way of implementing this variable number of UIViews, and why?
EDIT:
While I think that the layout of the cell here is irrelevant, it's been requested that I post it
so here it is...
I propose Solution 3, as it will be much more performant.
Also, I have two advices:
Avoid using UIStackView, as it has slow layout performance (it is based on AutoLayout). Also, try to avoid AutoLayout in UITableViewCell and UICollectionViewCell for better performance. Here are some of the most popular and powerful open source layout libraries PinLayout, LayoutKit.
You can write base UICollectionViewCell, move all of the relevant logic there, and then just make all the needed subclasses with minimal logic overriding.

When to use UICollectionView instead of UITableView?

I found that UICollectionView is like an upgraded version of UITableView introduced in iOS6, but when should I choose UICollectionView instead of UITableView?
There are still Apps using UITableView, if UICollectionView can do anything UITableView can do , why people still use UITableView? Is there a difference as far as performance is concerned?
Thanks!
That depends on the requirements. How the application flows determines which type of UI to integrate into the application.
People mainly use the UICollectionview for creating types of UIs with multiple images shown in a grid. This would have complex logic using UITableView, but with UICollectionview, it would be easy.
When using UICollectionview, you don't need to set buttons with tags or other things by getting selected items values. You can simply get -(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath and in UITableViewDelegate:
`-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath`
You get the selected row instead of the item, so for creating grid or modified items, using UICollectionview is best.
For the listing details of each item, people use UITableView because it shows more info on each item.
Apple Docs:
UICollectionView Class Reference
The UICollectionView class manages an ordered collection of data items and presents them using customizable layouts. Collection views provide the same general function as table views except that a collection view is able to support more than just single-column layouts. Collection views support customizable layouts that can be used to implement multi-column grids, tiled layouts, circular layouts, and many more. You can even change the layout of a collection view dynamically if you want.
UITableView Class Reference
A table view displays a list of items in a single column. UITableView is a subclass of UIScrollView, which allows users to scroll through the table, although UITableView allows vertical scrolling only. The cells comprising the individual items of the table are UITableViewCell objects; UITableView uses these objects to draw the visible rows of the table. Cells have content—titles and images—and can have, near the right edge, accessory views. Standard accessory views are disclosure indicators or detail disclosure buttons; the former leads to the next level in a data hierarchy and the latter leads to a detailed view of a selected item. Accessory views can also be framework controls, such as switches and sliders, or can be custom views. Table views can enter an editing mode where users can insert, delete, and reorder rows of the table.
Here's my criteria:
If a UITableView can do it, use it
If a UITableView needs lots of code to do it or can't do it at all, use UICollectionView.
You have to consider the restrictions on UITableView before making a decision: It's a single column. And you can only customize the cells, but not section backgrounds and such. So if you have a straight-up list of things with no extra frills - that looks like a bog standard iOS view, basically - then use UITableview. If you have custom insets, or a border around each section, use UICollectionView.
I'm actually considering UICollectionView for all things simply because it's very expensive when you start developing your view as a table view, then later find out it can't do that one thing that you need it to do. 1st hand experience ;)
Edit after even more experience with the two: Disregard that last paragraph. UICollectionView requires a lot of boilerplate code to make it work like a UITableView. Use UICollectionView only when really needed. ;)
For simple lists and forwards/backwards navigtaion, use UITableView.
If you need a high degree of customisability, use UICollectionView.
Generally speaking, in software development, it's best to choose the approach which represents "The Simplest Possible Thing".
EDIT: As of iOS 14, UICollectionView can now do lists as well and is now the recommended approach. See this session from WWDC20 for more information and implementation details: https://developer.apple.com/videos/play/wwdc2020/10026/
According to my point of view main difference between collectionView and tableView is that
TABLEVIEW --> show list of items in only one column.
COLLECTION-VIEW -->show list of items in multiple column.
Hope it will help you.
If you choose UITableView for iPhone, make sure you have considered your iPad strategy first. If you want an iPad-specific layout, you may want that single-column layout to become a grid.
Although it's not required, I always use a collectionview. That way I can easily adapt how my collections are presented for differing resolutions. A plus is that it's ready to quickly add new types of cells when refactoring in the future.
I see no point of tableviews. It's very simple to use a collection view to represent a table. IMO.
From my personal experience the two elements should only be compared loosly.
TableView
A TableView is a UI element designed for showing data in a list format. There is certain functionality that comes as standard with a UITableView, such as:
Accessory View
Cell Selection Style
Editting Style (Delete and edit buttons).
The above elements enhance the usability of data when displaying and interacting in a list format. Such as viewing emails.
CollectionView
A CollectionView is a UI element designed for showing content using a custom layout (usually anything that isn't a list). CollectionViews improve functionality of displaying data in completely bespoke layout styles and also dynamically changing layouts on the fly. Some examples are:
Horizonal Lists
Photo Galleries
Thumbnail views
Carousels
Dials
Laying out elements on a map
etc.
CollectionViews also allow for multiple selections.
Conclusion
As you can see from the above, both have completely different use cases and are designed for enhancing the development and usability of their own specific data sets.
If you are looking at displaying anything in a list style with the followin interactions:
- Adding
- Deleting
- Re-ordering
Then a UITableView will simplify this process by providing the support straight out of the box.
Anything else, you should leverage the benefits of CollectionView as you have more flexibility.
Its totally dependent on how your data to be shown.
As mentioned by many above, if you require only single set of data and that too not complex, go for UITableView else use UICollectionView.
UICollectionView is customization friendly.
If you are dealing with multiple cell heights or so, then go for UICollectionView.
Both are depends on the requirements. Table Views also have support for a variety of editing scenarios. This support has not been implemented in the Collection View classes.
If you are converting from a Table View that relies on these methods, expect to do a little extra heavy lifting in the Collection View.
Collection View section headers can be placed anywhere within the view.
and UITableView don't need to set buttons with tags or other things by getting selected items values.
In practice, everyone uses UICollectionView that I've come across, when they only need a UITableView. "It's one-dimensional. It goes up and down. Why are you adding unnecessary delegate methods for layout AND data?". I once spent an extra 2 hours helping a startup find out why their UICollectionViewCell got squished because the owner, who didn't read the Animations manual, nor HIG, nor the UICollectionView guide, decided to use it and add variable heights and anims. Needless to say, he gave himself a headache and much lost time on a non-business-critical issue he could have avoided by simply using a table cell, since there's no extra layout delegate + Nib.
Let me get this straight, I am all for UICollectionView's when your data and display need it. They're very powerful. But in practice, most people I've seen have been using them on lists.
This brings up another flaw. They're also used on short, constant lists that won't change, ever. In this case, just make a Xib. Or write a custom view that stacks them. Why? Because you don't need the memory management for 5 sets of labels with a button or switch. If they might change, then yes, use a list. If you want physics, then UICollectionView works well with a some cool effects. But do you really need to add 5 delegate methods and a layout system for 5 labels that will never move?
Also, I'm not forgetting that iOS has a native stacking view now too. I can never get it to deform how I want, even though I'm quite adept at the 2D and animation systems, so I never use the built-in one.
All I'm saying is, define your requirements. Maybe you don't need either of these, if your UI isn't adding/removing items and refreshing itself. Or maybe you want to write a Card Game and throw them out virtually on a table, then use UICollectionView with a physics system for its layout guide.
Personally I think the UICollectionView can do most of the work which UITableview can do. well, at the same time, it's more complex to use.
I suggest you use UICollectionView as TableView just in case your manager change requirements in the future.
Based on our need we are choosing TableView or CollectionView.
Example:
For phone contacts tableView is best option.
For photo gallery, collection view will be best option.
I had this issue in my current project. Which to use. In my case it was simple really. I needed both. I needed my view to look like UITableView and also to change its change / layout. So, UICollectionView was used. I also use UITableView everywhere I don't need any extra customisation. Since UiTableView comes with a default layout that includes images and text - I use it for simplicity.
Based on our requirement we choose UITableView or UICollection view.
If we want to display images or items in grid type or if we need more customisability we use UICollectionview.
For listing each item with details and subdetails we use UITableView.
UICollectionView:
The UICollectionView class manages an ordered collection of data items and presents them using customizable layouts. Collection views provide the same general function as table views except that a collection view is able to support more than just single-column layouts.
UITableView: A table view displays a list of items in a single column. UITableView is a subclass of UIScrollView, which allows users to scroll through the table, although UITableView allows vertical scrolling only.
As per my view for Grid View display use UI Collection View.All other list view use UITable View

iOS Design implementation recommandations

I would like to know how to handle, for my iOS app, the following situation:
I have to deal with something like this (basicly this is an article with comments, received from a server):
=- Text and Images -=
=- UIWebView -=
=- List of Comments -=
Now, I came up with two solutions:
Have the content above the list of comments wrapped in a UIScrollView, and create Views for each and everyone of the comments (don't know many of them could be), and
Make the list of comments a UITableView, and the above content its Header.
Which of these (or possibly another if you have any recommandations) should I choose? It may look not very important, but I would like to know this, so I could use the idea in further developing.
I would use a UITableView with a custom UITableViewCell wich holds the comments.
It will definitely have a better performance the UITableView than the UIScrollView since the UITableView re-uses the cells.
Using a UITableView you will just have to worry about customising the cells for the comments.
Otherwise if you want to use the UIScrollView in case you have a lot of comments you will have to create manually a way to reuse them which is what the UITableView does.
If you want something like facebook, so that the context + comments both are movable,then go with option 2.
But, if you want content always at the top, go with option 1.
Indeed, UITableView is a subclass of UIScrollView.
And If you think you might have many comments like (50+),
If you use scrollView, then you should have to supply scrollView with those number of UIView objects.
But, if you use tableView, it perfectly reused already created views.So evenhough you have 1000+ comments, it just uses 5 UIView objects

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