To bind a property of a visual elementA node of a visual tree that instantiates or derives from the C# VisualElement
class. You can style the look, define the behaviour, and display it on screen as part of the UI. More info
See in Glossary to a data source in C#, create an instance of DataBinding
. With this binding type, you can define a dataSource
and a dataSourcePath
directly on the binding instance.
To create a runtime binding in C#, follow these steps:
The following example created a binding object and registers it to a visual element.
var dataSource = ScriptableObject.CreateInstance<ExampleObject>(); var root = new VisualElement { name = "root", dataSource = dataSource }; var vector3Field = new Vector3Field("Vec3 Field"); vector3Field.SetBinding("label", new DataBinding { dataSourcePath = new PropertyPath(nameof(ExampleObject.vector3Label)), bindingMode = BindingMode.ToTarget }); vector3Field.SetBinding("value", new DataBinding { dataSourcePath = new PropertyPath(nameof(ExampleObject.vector3Value)) }); root.Add(vector3Field); var floatField = new FloatField("Float Field") { value = 42.2f }; floatField.SetBinding("value", new DataBinding { dataSourcePath = new PropertyPath(nameof(ExampleObject.sumOfVector3Properties)) }); root.Add(floatField); var label = new Label("Label") { dataSourcePath = new PropertyPath(nameof(ExampleObject.dangerLevel)) }; // Here, we do not need to set the dataSourcePath because we will only use two bindings and they will use the same path, // so we set the dataSourcePath on the Label directly instead. var binding = new DataBinding { bindingMode = BindingMode.ToTarget }; // Add a custom float -> string converter binding.sourceToUiConverters.AddConverter((ref float v) => { return v switch { >= 0 and < 1.0f/3.0f => "Danger", >= 1.0f/3.0f and < 2.0f/3.0f => "Neutral", _ => "Good" }; }); // Add a custom float -> StyleColor binding.sourceToUiConverters.AddConverter((ref float v) => new StyleColor(Color.Lerp(Color.red, Color.green, v))); // Since the binding is targeting the same data source property, we can reuse the same instance. label.SetBinding("text", binding); label.SetBinding("style.backgroundColor", binding); root.Add(label);
It’s equivalent to the following UXML:
<ui:UXML xmlns:ui="UnityEngine.UIElements" xmlns:uie="UnityEditor.UIElements" xsi="http://www.w3.org/2001/XMLSchema-instance" engine="UnityEngine.UIElements" editor="UnityEditor.UIElements" noNamespaceSchemaLocation="../UIElementsSchema/UIElements.xsd" editor-extension-mode="False"> <ui:VisualElement data-source="ExampleObject.asset" name="VisualElement" > <ui:Vector3Field label="Vec3 Field"> <Bindings> <ui:DataBinding property="label" data-source-path="vector3Label" binding-mode="ToSource" /> <ui:DataBinding property="value" data-source-path="vector3Value" /> </Bindings> </ui:Vector3Field> <ui:FloatField label="Float Field" value="42.2"> <Bindings> <ui:DataBinding property="value" data-source-path="sumOfVector3Properties" binding-mode="ToTarget" /> </Bindings> </ui:FloatField> <ui:Label text="Label" data-source-path="dangerLevel"> <Bindings> <ui:DataBinding property="text" binding-mode="ToTarget" source-to-ui-converters="Value To Progress" /> <ui:DataBinding property="style.backgroundColor" binding-mode="ToTarget" source-to-ui-converters="Value To Progress" /> </Bindings> </ui:Label> </ui:VisualElement> </ui:UXML>
You can use the following methods to manage binding objects:
You can create the bindable properties in the same way as other data sources, which means that you can also use VisualElement
types as data sources. The main difference between a VisualElement
type and other data sources is that VisualElement
types come with built-in versioning. You must use the built-in versioning of a VisualElement
type to propagate changes.
To report a change, call the NotifyPropertyChanged
method. This method takes a BindingId
that identifies the property that changed.
The following example shows how to report a change for a VisualElement
type:
// Creates a static readonly BindingId that is unique to this type. This is used to identify the property. public static readonly BindingId intValueProperty = nameof(intValue); private int m_IntValue; [CreateProperty] public int intValue { get => m_IntValue; set { if (m_IntValue == value) return; m_IntValue = value; // This instructs the binding system that a change occured. NotifyPropertyChanged(intValueProperty); } }
Follow these tips and best practices to optimize performance:
value
property of a Vector3Field
, the binding ID must be Vector3Field.valueProperty
.x
, y
, and z
sub-elements for a Vector3Field
. Instead, use a binding to synchronize the value
property of the Vector3Field
with a Vector3
property of a data source.UI Toolkit doesn’t report changes in element.style
and element.resolvedStyle
. Therefore, you can use binding instances to target the resolved style of an element but can’t track changes to them.
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