Technical users can define the layout of the UI directly in C# scripts.
You can define the look of controls in a USS file, or modify the style properties of the control in your C# script.
Controls are interactive and represent a value that you can change. For example, a FloatField represents a float value. You can create C# scripts to change the value of a control, register a callback, or apply data binding.
To use a control in a UI, add it to the visual tree.
The following example adds a Button control to an existing visual tree.
var newButton = new Button("Click me!");
rootVisualElement.Add(newButton);
When adding controls to a UI hierarchy, the layout engine automatically handles the sizing and positioning. You can also override the size and position of visual elements.
To access or change the value of a control, use its value property.
The following example creates a Toggle control and a Button control. When you click the button, the value of the toggle flips.
// 创建一个开关并注册回调
m_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };
rootVisualElement.Add(m_MyToggle);
// 创建切换开关值的按钮
Button button01 = new Button() { text = "Toggle" };
button01.clicked += () =>
{
m_MyToggle.value = !m_MyToggle.value;
};
rootVisualElement.Add(button01);
For more information about the properties of a specific control, see UI Toolkit built-in controls reference.
Controls that have value properties send an event if the value changes. You can register a callback to receive this event.
The following example creates a Toggle control and registers a callback:
// 创建一个开关并注册回调
m_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };
m_MyToggle.RegisterValueChangedCallback((evt) => { Debug.Log("Change Event received"); });
rootVisualElement.Add(m_MyToggle);
要了解有关回调和事件的更多信息，请参阅事件处理。
You can bind controls to an object or a serialized property. For example, you can bind a FloatField control to a public float variable that belongs to a MonoBehaviour. When the control binds to the property, it automatically displays the value of the property. When you modify the control, the value of the property updates.
Similarly, when the property value changes through code, the UI displays the updated value. This two-way connection is useful when you create custom Inspector windows.
For more information about data binding, see SerializedObject data binding.
Not all controls are bindable. For a list of built-in controls and whether they support binding, see UI Toolkit built-in controls reference.
Some controls have read-only child elements. For example, a ListView control has a ScrollView child. You can use UQuery to access the child’s properties and override their values.
The following example changes the scroll speed of a ListView control by overriding the mouseWheelScrollSize property of the ScrollView child:
var scrollView = listView.Q<ScrollView>();
scrollView.mouseWheelScrollSize = 55;
Controls have different states that you can manage in your C# scripts. For example, you can enable or disable a control.
The following example creates a Toggle control and a Button control. When you click the button, the toggle is disabled.
// Create a toggle.
Toggle myToggle = new Toggle("A Toggle");
// Create a button to disable the toggle.
Button button01 = new Button();
button01.text = "Button01";
button01.RegisterCallback<ClickEvent>(evt =>
{
myToggle.SetEnabled(false);
});
You can also implement a visual feedback change when the state changes in USS using the pseudo-classes. For example, to disable a toggle, use a selector that has the disabled pseudo state:
.unity-button:disabled
{
background-color: #000000;
}