zkamsler / VirtualList

An efficient virtual list view for Unity uGUI UI

VirtualList

An efficient virtual list view for Unity uGUI UI

The virtual list view allows display of large scrolling lists or grids while only instantiating enough elements to show what is on screen at a given time.

Basic Usage

Types of components

• VirtualGridList => grid or vertical/horizontal list with fixed sized elements (probably fine for most use-cases)
• VirtualVerticalList => vertical list that fits width of elements to parent
• VirtualHorizontalList => horizontal list that fits height of elements to parent

In the scene

1. Add the desired component on the gameobject for the list root. This is the view inside the scroll rect, which might have otherwise contained a layout group.
2. Set up references to scroll rect and tile prefab
3. Set up sizing as desired
4. Remove any layout and ContentSizeFitter components.
5. Remove any children of the list root. These are not automatically cleared, and their instantiation has a cost.

Sources

The virtual list takes a IListSource that describes what data to use. You can manually implement the interface, or you can use the SimpleSource in noninteractive cases.

IPrefabSource

An IListSource can optionally implement IPrefabSource, allowing you to use multiple different prefabs for list elements.

Using in code

• add using VirtualList;
• Add AbstractVirtualList variable in panel (and hook it up)
• Call SetSource to make it show the source
• Call Clear() on the list in the panel’s OnExit

Misc

• You can use the SetSourceAndCenterOn method to set the source and center on a specific index in a single step (when desired). If done separately, it would populate views for the old scroll position, and then potentially throw them away.

Installation

You can copy the files, or add this repo as a dependency in the Unity package manager. There are no external dependencies, so it is pretty simple.

Caveats

• All elements of a given list must have the same size and spacing. The list relies on this to be able to efficiently calculate what would be visible at a given scroll position.
• Instantiated list elements are reused without paying the cost of disabling the game object. But sometimes they will be disabled if there are not enough elements on screen, which is a bit more expensive. This can happen more often if a IPrefabSource is used with a mix of different prefabs.

Examples

See Samples~/Sample1 folder

License

MIT