UXML element DropdownField

A DropdownField lets users choose a value from a list. When clicking on the control, it opens a drawer that presents multiple options, allowing users to select one. If you want to always display all the choices, use RadioButtonGroup.

Note: To align an element with other fields in an InspectorA 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 window, simply apply the .unity-base-field__aligned USS class to it. For more information, refer to BaseField.

Create a DropdownField

You can create a DropdownField with UI(User Interface) Allows a user to interact with your application. Unity currently supports three UI systems. More info
See in Glossary Builder, UXML, or C#.

UI Builder

To add options for a DropdownField in UI Builder, in the Inspector panel of the DropdownField, enter the options separated by commas in Choices.

To set the default value, in the Inspector of the DropdownField, enter the numbering sequence of the option in Index, starting at 0.

C#

The following C# example create a DropdownField with three options. The DropdownField selects the first option by default:

var dropdown = new DropdownField("Options", new List<string> { "Option 1", "Option 2", "Option 3" }, 0);

//Add another option
dropdown.choices.Add("Option 4");

// To return int value instead of string
dropdown.index = 1; // Option 2
dropdown.value = "Option3";
Assert.IsTrue(myDropdown.index == 2);

// Register to the value changed callback
dropdown.RegisterValueChangedCallback(evt => Debug.Log(evt.newValue));

Change styles for a DropdownField

You can override the default Panel Settings fields in a USS file to change the styles of a DropdownField:

1. In the Hierarchy window, select your UI Document (.uxml).
2. Set Panel Settings as your Panel Settings asset. If you don’t have an existing Panel Settings asset, follow the instructions in the dialog to create one.
3. In your Panel Settings asset, assign a Theme Style Sheet.
4. In the Project window, select your TSS file.
5. Go to Style Sheets and select the Add (+) button.
6. Set your Style Sheet as your USS file.

Examples

The following UXML example creates a DropdownField:

<UXML xmlns="UnityEngine.UIElements" xmlns:uie="UnityEditor.UIElements">
    <DropdownField label="UXML Field" name="the-uxml-field" />
</UXML>

The following C# example illustrates some of the customizable functionalities of the DropdownField:

/// <sample>
// You can provide the list of choices by code, or by comma separated values in UXML
// <DropdownField .... choices="Option 1,Option 2,Option 3" .... />
var choices = new List<string> { "Option 1", "Option 2", "Option 3" };

// Get a reference to the dropdown field from UXML and assign a value to it.
var uxmlField = container.Q<DropdownField>("the-uxml-field");
uxmlField.choices = choices;
uxmlField.value = choices[0];

// Create a new dropdown with the same choices, disable it, and give it a style class.
var csharpField = new DropdownField("C# Field", choices, 0);
csharpField.SetEnabled(false);
csharpField.AddToClassList("some-styled-field");
container.Add(csharpField);

// Mirror the value of the UXML field into the C# field.
uxmlField.RegisterCallback<ChangeEvent<string>>((evt) =>
{
    csharpField.value = evt.newValue;
});
/// </sample>

To try this example live in Unity, go to Window > UI Toolkit > Samples.

C# base class and namespace

C# class: DropdownField
Namespace: UnityEngine.UIElements
Base class: PopupField_1

Inherited UXML attributes

This element inherits the following attributes from its base class:

Name	Type	Description
binding-path	string	Path of the target property to be bound.
choices	IList	The list of choices to display in the popup menu.
focusable	boolean	True if the element can be focused.
index	int	The currently selected index in the popup menu. Setting the index will update the ::ref::value field and send a property change notification.
label	string	The string representing the label that will appear beside the field.
tabindex	int	An integer used to sort focusables in the focus ring. Must be greater than or equal to zero.
value	int	The currently selected value in the popup menu.

This element also inherits the following attributes from VisualElement:

Name	Type	Description
content-container	string	Child elements are added to it, usually this is the same as the element itself.
data-source	Object	Assigns a data source to this VisualElement which overrides any inherited data source. This data source is inherited by all children.
data-source-path	string	Path from the data source to the value.
data-source-type	System.Type	The possible type of data source assignable to this VisualElement. This information is only used by the UI Builder as a hint to provide some completion to the data source path field when the effective data source cannot be specified at design time.
language-direction	UIElements.LanguageDirection	Indicates the directionality of the element’s text. The value will propagate to the element’s children. Setting the languageDirection to RTL adds basic support for right-to-left (RTL) by reversing the text and handling linebreaking and word wrapping appropriately. However, it does not provide comprehensive RTL support, as this would require text shaping, which includes the reordering of characters, and OpenType font feature support. Comprehensive RTL support is planned for future updates, which will involve additional APIs to handle language, script, and font feature specifications. To enhance the RTL functionality of this property, users can explore available third-party plugins in the Unity Asset Store and make use of ITextElementExperimentalFeatures.renderedText
name	string	The name of this VisualElement. Use this property to write USS selectors that target a specific element. The standard practice is to give an element a unique name.
picking-mode	UIElements.PickingMode	Determines if this element can be pick during mouseEvents or IPanel.Pick queries.
style	string	Sets the VisualElement style values.
tooltip	string	Text to display inside an information box after the user hovers the element for a small amount of time. This is only supported in the Editor UI.
usage-hints	UIElements.UsageHints	A combination of hint values that specify high-level intended usage patterns for the VisualElement. This property can only be set when the VisualElement is not yet part of a Panel. Once part of a Panel, this property becomes effectively read-only, and attempts to change it will throw an exception. The specification of proper UsageHints drives the system to make better decisions on how to process or accelerate certain operations based on the anticipated usage pattern. Note that those hints do not affect behavioral or visual results, but only affect the overall performance of the panel and the elements within. It’s advised to always consider specifying the proper UsageHints, but keep in mind that some UsageHints might be internally ignored under certain conditions (e.g. due to hardware limitations on the target platform).
view-data-key	string	Used for view data persistence, such as tree expanded states, scroll position, or zoom level. This key is used to save and load the view data from the view data store. If you don’t set this key, the persistence is disabled for the associated VisualElement. For more information, refer to View data persistence.

USS classes

The following table lists all the C# public property names and their related USS selector.

C# property	USS selector	Description
ussClassName	.unity-popup-field	USS class name of elements of this type.
labelUssClassName	.unity-popup-field__label	USS class name of labels in elements of this type.
inputUssClassName	.unity-popup-field__input	USS class name of input elements in elements of this type.
ussClassName	.unity-base-popup-field	USS class name of elements of this type.
textUssClassName	.unity-base-popup-field__text	USS class name of text elements in elements of this type.
arrowUssClassName	.unity-base-popup-field__arrow	USS class name of arrow indicators in elements of this type.
labelUssClassName	.unity-base-popup-field__label	USS class name of labels in elements of this type.
inputUssClassName	.unity-base-popup-field__input	USS class name of input elements in elements of this type.
ussClassName	.unity-base-field	USS class name of elements of this type.
labelUssClassName	.unity-base-field__label	USS class name of labels in elements of this type.
inputUssClassName	.unity-base-field__input	USS class name of input elements in elements of this type.
noLabelVariantUssClassName	.unity-base-field--no-label	USS class name of elements of this type, when there is no label.
labelDraggerVariantUssClassName	.unity-base-field__label--with-dragger	USS class name of labels in elements of this type, when there is a dragger attached on them.
mixedValueLabelUssClassName	.unity-base-field__label--mixed-value	USS class name of elements that show mixed values
alignedFieldUssClassName	.unity-base-field__aligned	USS class name of elements that are aligned in a inspector element
disabledUssClassName	.unity-disabled	USS class name of local disabled elements.

You can also use the Matching Selectors section in the Inspector or the UI Toolkit Debugger to see which USS selectors affect the components of the VisualElement at every level of its hierarchy.

Additional resources

• RadioButtonGroup