5/1/2023 0 Comments Flowlayout ios![]() ![]() UICollectionViewLayout is an abstract class, and any subclass has to implement a few documented methods for it to be usable: If you encounter this issue then you can move your layout code to the Sources folder of your playground, where it will be compiled, and will run much faster. However, most of this is due to the nature of playgrounds, particularly the live output and logging of each line of code in the page. One drawback of the playgrounds approach is that things can get worryingly slow - for some layouts there can be a lot of back and forth as attributes are invalidated and recalculated, and you may find yourself thinking that you’re developing something unusable. The Previewing page of the playground demonstrates how to make an interactive, scrollable collection view right there in your playground. ![]() The layouts included in the playground are designed with code readability and learning in mind, to use them in production may require performance optimisations or other changes. It’s easy to stand up a simple data source object which returns plain or very simple cells, which you could perhaps tint with colours to let you know where things are going.Īccompanying this article is an Xcode playground demonstrating the code and principles discussed. Using the live view feature you can add a collection view to the assistant area and watch it develop as you work on your layout. Xcode playgrounds are an excellent place to develop a custom layout. These features are not difficult to implement yourself.īuilding a custom layout can be complex, and it’s important to be able to quickly iterate when working. Don’t use the flow layout just to get some of its features, like floating section headers. If your layout uses regular, predictable, but non-uniform sizes then a custom layout is also a good choice. If your layout is more complicated than “fit these cells in a line, breaking when you get to the edge of the screen”, or you’re not happy with the decisions that flow layout makes about your cells (for example, the forced “justification” of cells) then you may want to consider a custom layout. ![]() Custom invalidation contexts and their uses for floating views and autoresizing.How a layout works, and the layout lifecycle.You’re going to learn about the following interesting but poorly documented areas of collection view layouts: The flow layout achieves all it does using the same API that is available to you as a third party developer, but it’s not immediately clear how you would create something like the flow layout yourself. However, getting things for free usually has a price - in this case, the price is a lack of decent understanding of what a collection view layout does or how it works. Automatic resizing to deal with cells that size themselves using auto layout.Section headers and footers, with the option to pin these to the visible bounds to make them “float”.Layout of your items into organised rows and columns, with configurable spacing and alignment.This covers a lot of use cases, and delivers you the following advanced features for free, or almost free: The flow layout does a lot of heavy lifting for you when you’re dealing with a flexible number of arbitrarily sized items that need to make room for each other. ![]() But this versatility comes with a price - collection views, and particularly collection view layouts, can become complicated, and the official documentation for some of the more interesting areas is a little… sparse.Īpple frequently tells you to use directly or subclass the flow layout. 그래서 FlowLayout이라고 불리는 듯 하다.ĬollectionView 프로퍼티를 설정한다.Going Without the Flow - Exploring Collection View LayoutsĬollection views are extremely versatile - there’s even speculation that the venerable UITableView will be soft-deprecated in favour of its more flexible and powerful cousin. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |