Create custom item renderers for Feathers UI data containers
By default, any container that renders a data collection (such as ListView or GridView) uses the ItemRenderer class to display each item from its collection. However, translating from design to code sometimes requires more advanced capabilities for layout and styling than the basic ItemRenderer can provide. In these situations, a developer can create a custom item renderer for the data container.
Generally, the easiest option for creating a custom item renderer is using LayoutGroupItemRenderer. This component provides the same background skins with multiple states as ItemRenderer, but it is based on the LayoutGroup component, which allows any number of children to be added with support for layouts.
However, any Feathers UI component may be used to create a custom item renderer. Want to use a Check or a PopUpListView? No problem!
Create in a function
Any Feathers UI component may be used as a custom item renderer by instantiating it inside a function passed to DisplayObjectRecycler.withFunction().
The example below creates a LayoutGroupItemRenderer with a Label subcomponent to display some text.
var recycler = DisplayObjectRecycler.withFunction(() -> {
var itemRenderer = new LayoutGroupItemRenderer();
var label = new Label();
label.name = "label";
itemRenderer.addChild(label);
return itemRenderer;
});
recycler.update = (itemRenderer:LayoutGroupListItemRenderer, state:ListViewItemState) -> {
var label = cast(itemRenderer.getChildByName("label"), Label);
label.text = state.data.title;
});
listView.itemRendererRecycler = recycler;
Create a subclass
It's also possible to extend any Feathers UI component to create a custom item renderer. The example below creates a subclass of LayoutGroupItemRenderer that works similarly to the custom item renderer in the previous example.
class MyCustomItemRenderer extends LayoutGroupItemRenderer {
public function new() {
super();
}
private var label:Label;
override private function initialize():Void {
super.initialize();
label = new Label();
addChild(label);
}
override private function update():Void {
var dataInvalid = isInvalid(DATA);
if (dataInvalid) {
if (data != null) {
label.text = data.title;
}
else {
label.text = null;
}
}
super.update();
}
}
Pass the subclass to DisplayObjectRecycler.withClass() to use it with a data container.
listView.itemRendererRecycler = DisplayObjectRecycler.withClass(MyCustomItemRenderer);
For more details about managing the custom item renderer's data within a subclass of another component, see Class-based custom item renderers.
Should I use a function or class?
Using a function or class largely depends on developer preference, and also how complicated the custom item renderer implementation needs to be. A function works best for simple custom item renderers with a small number of sub-components and not much in the way of custom user interaction. A subclass is better for a custom item renderer that might need event listeners, a lot of children, or if it might change state based on data changes or user interaction.