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Unity Engine

Contextual menu events

Events that occur when the user interacts with a contextual menu.
読み終わるまでの所要時間 3 分最終更新 1ヶ月前
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.

Enable contextual menus

To enable contextual menus, attach the 
ContextualMenuManipulator
 to a visual element. 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 evt){    // Modify evt.menu    evt.menu.AppendAction("My action", DisplayProperties, DropdownMenuMenuAction.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 tree 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.

Respond to the user selection

When an element receives a 
ContextualMenuPopulateEvent
, it calls either 
DropdownMenu.InsertAction()
 or 
DropdownMenu.AppendAction()
 to add menu items to the contextual menu. 
DropdownMenu.InsertAction()
 and 
DropdownMenu.AppendAction()
 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.

Examples

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.
  1. Create a Unity project with any template.
  2. In the Project window, create a folder named 
    Editor
    .
  3. In the 
    Editor
    window, create a C# script named 
    ContextualMenuDemo.cs
    with the following content:
    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);        });    }}
  4. To see the example live, from the menu, select Window > UI Toolkit > ContextualMenuDemo.

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