Create a tabbed menu for runtime

Version: 2021.3+

Tabbed menus are common in video games and application UI. You can use UI Toolkit to create a tabbed menu for a custom Editor window or runtime. This example demonstrates how to create a tabbed menu in the sample scene.

Example overview

This example adds a menu in the sample scene. The menu has three tabs. Each tab presents certain content. When you click a tab, only the content associated with that tab is displayed.

To create tabbed content, you need to define the menu elements, styles, and logic.

You can find the completed files that this example creates in this GitHub repository.

先决条件

This guide is for developers familiar with Unity, UI Toolkit, Flexbox, and C# scripting. You are recommended to have a basic understanding of the following concepts:

Define the tabbed menu elements

Create two sections in your menu using the UI Builder, one for tabs and one for the content of tabs. In these sections, create three tab elements and three tab content elements.

Create a project in Unity with any template.
Click GameObject > UI Toolkit > UI Document to add a UI Document in the sample scene.
Create a folder in Assets named TabbedMenu to store all your files.
In the TabbedMenu folder, create a UI Document named TabbedMenu.uxml.
Double-click TabbedMenu.uxml to open it in the UI Builder.
Add two VisualElements named tabs and tabContent under the root.
Under tabs, add three Label controls and give them the following Label texts:
- London
- Paris
- Ottawa
Under tabContent, add three Label controls and give them the following Label texts:
- London is the capital city of England
- Paris is the capital of France
- Ottawa is the capital of Canada
To associate the tab content with the tab, this example uses the same prefixes but different suffixes for the Label names. Each tab name has the Tab suffix and each tab content has the Content suffix. Set the tab Label names and content Label names to the following:
- LondonTab
- ParisTab
- OttawaTab
- LondonContent
- ParisContent
- OttawaContent

Your UI Builder Hierarchy looks like the following:

Define the tabbed menu styles

Define the layout for tabs and tab content using USS. You can style the tabs and the tab content the way you like. This example arranges tabs in a row and on top of the tab content. It adds a background color for the selected tab and hides the un-selected tab content.

In the TabbedMenu folder, create a stylesheet named TabbedMenu.uss.

Open TabbedMenu.uss and add the following styling rules:

/* Style for tabs */
#tabs {
    flex-basis: 10%;
    flex-direction: row;
    background-color: rgb(229, 223, 223);
    -unity-font-style: bold;
    font-size: 14px;
}

/* Sets each label in tabs to have the same size. */
.tab {
    flex-grow: 1;
}

/* Adds background color for the selected tab */
.currentlySelectedTab {
    background-color: rgb(173, 166, 166);
}

/* Style for tabContent */
#tabContent {
    flex-basis: 90%;
    background-color: rgb(255, 255, 255);
    font-size: 20px;
}

/* Hides the unselected tab content */
.unselectedContent {
    display: none;
}

Open TabbedMenu.uxml in UI Builder.
Click Add Existing USS and select TabbedMenu.uss.
Apply your styles to the UI controls:
- Apply .tab to each label under tabs
- Apply .currentlySelectedTab to LondonTab
- Apply .unselectedContent to ParisContent and OttawaContent

The finished TabbedMenu.uxml looks like the following:

<ui:UXML xmlns:ui="UnityEngine.UIElements" xmlns:uie="UnityEditor.UIElements" xsi="http://www.w3.org/2001/XMLSchema-instance" engine="UnityEngine.UIElements" editor="UnityEditor.UIElements" noNamespaceSchemaLocation="../../../UIElementsSchema/UIElements.xsd" editor-extension-mode="False">
   /* Your src might look different. If you save your UXML in UI Builder, USS file is referenced by the file location, fileID and guid. */
   <Style src="TabbedMenu-style.uss" />
   <ui:VisualElement name="tabs">
      <ui:Label name="LondonTab" text="London" class="tab currentlySelectedTab" />
      <ui:Label name="ParisTab" text="Paris" class="tab" />
      <ui:Label name="OttawaTab" text="Ottawa" class="tab" />
   </ui:VisualElement>
   <ui:VisualElement name="tabContent">
      <ui:Label text="London is the capital city of England" name="LondonContent" />
      <ui:Label text="Paris is the capital of France" name="ParisContent" class="unselectedContent" />
      <ui:Label text="Ottawa is the capital of Canada" name="OttawaContent" class="unselectedContent" />
   </ui:VisualElement>
</ui:UXML>

Set up the scene

Create a UIDocument GameObject in the SampleScene and add the UI Document as the source asset.

In the SampleScene, select GameObject > UI Toolkit > UI Document.
Select the UIDocument GameObject in the hierarchy and drag TabbedMenu.uxml from your Project window to the Source Asset field of the UI Document component in the Inspector window. This references the source asset to the UXML file you created.

Define the tabbed menu logic

Create the C# scripts that change the displayed tab content. When a user clicks a tab, the tab’s content displays and the current content hides.

In the TabbedMenu folder, create a C# script namedTabbedMenu.cs with the following contents:

// This script attaches the tabbed menu logic to the game.
using UnityEngine;
using UnityEngine.UIElements;

//Inherits from class `MonoBehaviour`. This makes it attachable to a game object as a component.
public class TabbedMenu : MonoBehaviour
{
    private TabbedMenuController controller;

    private void OnEnable()
    {
        UIDocument menu = GetComponent<UIDocument>();
        VisualElement root = menu.rootVisualElement;

        controller = new(root);

        controller.RegisterTabCallbacks();
    }
}

Select UIDocument in the SampleScene and drag the TabbedMenu.cs to Add Component in the Inspector.

In the TabbedMenu folder, create a C# script named TabbedMenuController.cs with the following contents:

// This script defines the tab selection logic.
using UnityEngine.UIElements;

public class TabbedMenuController
{
    /* Define member variables*/
    private const string tabClassName = "tab";
    private const string currentlySelectedTabClassName = "currentlySelectedTab";
    private const string unselectedContentClassName = "unselectedContent";
    // Tab and tab content have the same prefix but different suffix
    // Define the suffix of the tab name
    private const string tabNameSuffix = "Tab";
    // Define the suffix of the tab content name
    private const string contentNameSuffix = "Content";

    private readonly VisualElement root;

    public TabbedMenuController(VisualElement root)
    {
        this.root = root;
    }

    public void RegisterTabCallbacks()
    {
        UQueryBuilder<Label> tabs = GetAllTabs();
        tabs.ForEach((Label tab) => {
            tab.RegisterCallback<ClickEvent>(TabOnClick);
        });
    }

    /* Method for the tab on-click event: 

       - If it is not selected, find other tabs that are selected, unselect them 
       - Then select the tab that was clicked on
    */
    private void TabOnClick(ClickEvent evt)
    {
        Label clickedTab = evt.currentTarget as Label;
        if (!TabIsCurrentlySelected(clickedTab))
        {
            GetAllTabs().Where(
                (tab) => tab != clickedTab && TabIsCurrentlySelected(tab)
            ).ForEach(UnselectTab);
            SelectTab(clickedTab);
        }
    }
    //Method that returns a Boolean indicating whether a tab is currently selected
    private static bool TabIsCurrentlySelected(Label tab)
    {
        return tab.ClassListContains(currentlySelectedTabClassName);
    }

    private UQueryBuilder<Label> GetAllTabs()
    {
        return root.Query<Label>(className: tabClassName);
    }

    /* Method for the selected tab: 
       -  Takes a tab as a parameter and adds the currentlySelectedTab class
       -  Then finds the tab content and removes the unselectedContent class */
    private void SelectTab(Label tab)
    {
        tab.AddToClassList(currentlySelectedTabClassName);
        VisualElement content = FindContent(tab);
        content.RemoveFromClassList(unselectedContentClassName);
    }

    /* Method for the unselected tab: 
       -  Takes a tab as a parameter and removes the currentlySelectedTab class
       -  Then finds the tab content and adds the unselectedContent class */
    private void UnselectTab(Label tab)
    {
        tab.RemoveFromClassList(currentlySelectedTabClassName);
        VisualElement content = FindContent(tab);
        content.AddToClassList(unselectedContentClassName);
    }

    // Method to generate the associated tab content name by for the given tab name
    private static string GenerateContentName(Label tab) =>
        tab.name.Replace(tabNameSuffix, contentNameSuffix);

    // Method that takes a tab as a parameter and returns the associated content element
    private VisualElement FindContent(Label tab)
    {
        return root.Q(GenerateContentName(tab));
    }
}

Enter Play mode and click different tabs to see different contents.

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