A control is an element of a graphical user interface, such as a button, label or checkbox. It includes the visuals of the control, and the scripted logic to operate and interact with the control.
In UI(User Interface) Allows a user to interact with your application. Unity currently supports three UI systems. More info
See in Glossary Toolkit, a control is similar to a PrefabAn asset type that allows you to store a GameObject complete with components and properties. The prefab acts as a template from which you can create new object instances in the scene. More info
See in Glossary, combining visual elements and scripting into a template you can use inside a UI panel.
Controls can consist of a single visual element, or a combination of multiple visual elements.
For example, the Toggle
control, shown above, contains three elements:
The implementation of the Toggle
control defines the behavior of the control. It has an internal value of whether the toggle state is true or false. This logic alternates the visibility of the checkmark image when the value changes.
To use a control in a UI, you need add it to a UI hierarchy, called the Visual Tree. You can add the control through a script, UXML, or in the UI Builder.
The code snippet below shows how to add 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. For more information about the automatic layout, see the Layout Engine.
You can also manually override the size and position of visual elements. To learn more about controlling the position manually, see the Visual Tree page.
All visual elements in UI Toolkit use styles to define their attributes. You can modify style properties in three ways:
Controls are interactive and represent a value that you can change. For example, a FloatField
represents a float value. You can use code to react to changes, such as:
If a control represents a modifiable value, it contains a value
property. ScriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary can use the value
property to directly access the value of the control. The code snippet below creates a Toggle
control and a Button
control. When you click the button, the value of the toggle flips.
// Create a toggle and register callback
m_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };
rootVisualElement.Add(m_MyToggle);
// Create button to flip the toggle's value
Button button01 = new Button() { text = "Toggle" };
button01.clicked += () =>
{
m_MyToggle.value = !m_MyToggle.value;
};
rootVisualElement.Add(button01);
To learn more about the properties of a specific control, see the UI Toolkit controls reference.
All built-in controls that have value
properties send an event if the value changes. The code can register a callback to receive this event. The following code snippet shows how to create a Toggle
control and register a callback:
// Create a toggle and register callback
m_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };
m_MyToggle.RegisterValueChangedCallback((evt) => { Debug.Log("Change Event received"); });
rootVisualElement.Add(m_MyToggle);
To learn more about callbacks and events, see Events Handling.
Controls can bind directly to an object or serialized property. For example, a FloatField
control can bind 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 the user modifies the control, the value of the property updates.
Similarly, when the property value changes via code, the UI displays the updated value. This two-way connection is useful when creating custom inspectorsA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary.
To learn more about data binding, see the Binding page.
Not all controls are bindable. To see a list of all built-in controls and whether they support binding, see the UI Toolkit controls reference.
UI Toolkit allows you to create custom controls. This makes it possible to create complex controls, or implement custom logic for user interface elements.
Controls derive directly from VisualElement
, or a subclass of VisualElement
, such as TextElement
. They might also add manipulators to implement the behavior of the control. For example, the Button
control adds a Clickable
manipulator.
Unity includes a large range of standard controls, such as labels, text fields, and toggles. Some controls are only available in the Editor. For a complete list of built-in controls for UI Toolkit, see the UI Toolkit controls reference.
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