Use the contextual menu events, ContextualMenuManipulator
and ContextualMenuPopulateEvent
, to display a set of choices when a user performs certain actions, such as when a user right-clicks a label.
To enable contextual menus, attach the ContextualMenuManipulator
to 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. This manipulator displays a contextual menu after either a right button mouse up event or a menu key up event. The ContextualMenuManipulator
manipulator also adds a callback that responds to a ContextualMenuPopulateEvent
.
The following code example adds a contextual menu to a visual element. The menu has only one item.
void InstallManipulator(VisualElement element)
{
ContextualMenuManipulator m = new ContextualMenuManipulator(MyDelegate);
m.target = element;
}
void MyDelegate(ContextualMenuPopulateEvent event)
{
// Modify event.menu
event.menu.AppendAction("My action", DisplayProperties, DropdownMenu.MenuAction.AlwaysEnabled);
}
void DisplayProperties(DropdownMenu.MenuAction menuItem)
{
// ...
}
The callback given to the ContextualMenuManipulator
constructor is invoked last so child elements can populate the menu.
The manipulator sends a ContextualMenuPopulateEvent
event propagated to the target element hierarchy. The event moves along the propagation path: from the root of the visual treeAn object graph, made of lightweight nodes, that holds all the elements in a window or panel. It defines every UI you build with the UI Toolkit.
See in Glossary to the event target, and then back up the visual tree to the root. Along the propagation path, the elements with a callback for the ContextualMenuPopulateEvent
event can add, remove, or update items in the contextual menu.
When an element receives a ContextualMenuPopulateEvent
, it calls either [DropdownMenu.InsertAction()
](../ScriptReference/UIElements.DropdownMenu.InsertAction] or DropdownMenu.AppendAction(.html)
to add menu items to the contextual menu.
[DropdownMenu.InsertAction()
](../ScriptReference/UIElements.DropdownMenu.InsertAction] and DropdownMenu.AppendAction(.html)
take two callbacks as parameters. The first callback executes when the user selects the item in the menu. The second callback executes before it displays the menu and also checks whether the menu item is enabled.
Both callbacks receive a MenuAction
as a parameter. The MenuAction
represents the menu item and has the following properties:
MenuAction.userData
includes a reference to user data used with AppendAction()
or InsertAction()
.MenuAction.eventInfo
includes information about the event that displays the contextual menu. Use MenuAction.eventInfo
in the action that responds to the event. For example, you can use the mouse position to create and place an object based on the selected contextual menu item.The following example creates a custom Editor window with two labels and adds contextual menus for each label. The example demonstrates how to add, remove, and update a contextual menu.
Create a Unity project with any template.
In the Project windowA window that shows the contents of your Assets
folder (Project tab) More info
See in Glossary, create a folder named Editor
.
In the Editor
window, create a C# script named ContextualMenuDemo
and replace its contents with the following:
using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;
public class ContextualMenuDemo : EditorWindow
{
[MenuItem("Window/ContextualMenuDemo")]
public static void ShowExample()
{
ContextualMenuDemo wnd = GetWindow<ContextualMenuDemo>();
wnd.titleContent = new GUIContent("ContextualMenuDemo");
}
public void CreateGUI()
{
VisualElement root = rootVisualElement;
VisualElement label = new Label("Right click me!");
root.Add(label);
AddANewContextMenu(label);
InsertIntoAnExistingMenu(label);
VisualElement second = new Label("Click me also!");
root.Add(second);
AddANewContextMenu(second);
InsertIntoAnExistingMenu(second);
// Override the default behavior by clearing the menu.
ReplaceContextMenu(second);
}
void AddANewContextMenu(VisualElement element)
{
// The manipulator handles the right click and sends a ContextualMenuPopulateEvent to the target element.
// The callback argument passed to the constructor is automatically registered on the target element.
element.AddManipulator(new ContextualMenuManipulator((evt) =>
{
evt.menu.AppendAction("First menu item", (x) => Debug.Log("First!!!!"), DropdownMenuAction.AlwaysEnabled);
evt.menu.AppendAction("Second menu item", (x) => Debug.Log("Second!!!!"), DropdownMenuAction.AlwaysEnabled);
}));
}
void InsertIntoAnExistingMenu(VisualElement element)
{
element.RegisterCallback<ContextualMenuPopulateEvent>((evt) =>
{
evt.menu.AppendSeparator();
evt.menu.AppendAction("Another action", (x) => Debug.Log("Another Action!!!!"), DropdownMenuAction.AlwaysEnabled);
});
}
void ReplaceContextMenu(VisualElement element)
{
element.RegisterCallback<ContextualMenuPopulateEvent>((evt) =>
{
evt.menu.ClearItems();
evt.menu.AppendAction("The only action", (x) => Debug.Log("The only action!"), DropdownMenuAction.AlwaysEnabled);
});
}
}
To see the example live, from the menu, select Window > UI Toolkit > ContextualMenuDemo.