Create a slide toggle custom control

Version: 2021.3+

This example demonstrates how to create a “switch-like” variation of a toggle.

Example overview

The example creates a custom control: a toggle that users can flip with the mouse, the keyboard, a gamepad, and other devices. It comes with a label that can describe what the toggle represents.

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 the Unity Editor, UI Toolkit, and C# scripting. Before you start, get familiar with the following:

• UI Builder
• Visual Tree
• UXML
• USS
• 处理事件

Create and style the slide toggle

Create the slide toggle class with a C# script and style it with a USS file.

1. Create a Unity project with the 3D template. A 3D template has a better visual effect for this example. However, you can use any templates.

2. Create a folder named slide-toggle to store your files.

3. In the slide-toggle folder, create a C# script named SlideToggle.cs.

4. Open SlideToggle.cs in a text editor and replace its content with the following:

   using UnityEngine;
   using UnityEngine.UIElements;
   
   namespace MyUILibrary
   {
       // Derives from BaseField<bool> base class. Represents a container for its input part.
       public class SlideToggle : BaseField<bool>
       {
           public new class UxmlFactory : UxmlFactory<SlideToggle, UxmlTraits> { }
   
           public new class UxmlTraits : BaseFieldTraits<bool, UxmlBoolAttributeDescription> { }
   
           // In the spirit of the BEM standard, the SlideToggle has its own block class and two element classes. It also
           // has a class that represents the enabled state of the toggle.
           public static readonly new string ussClassName = "slide-toggle";
           public static readonly new string inputUssClassName = "slide-toggle__input";
           public static readonly string inputKnobUssClassName = "slide-toggle__input-knob";
           public static readonly string inputCheckedUssClassName = "slide-toggle__input--checked";
   
           VisualElement m_Input;
           VisualElement m_Knob;
   
           // Custom controls need a default constructor. This default constructor calls the other constructor in this
           // class.
           public SlideToggle() : this(null) { }
   
           // This constructor allows users to set the contents of the label.
           public SlideToggle(string label) : base(label, null)
           {
               // Style the control overall.
               AddToClassList(ussClassName);
   
               // Get the BaseField's visual input element and use it as the background of the slide.
               m_Input = this.Q(className: BaseField<bool>.inputUssClassName);
               m_Input.AddToClassList(inputUssClassName);
               Add(m_Input);
   
               // Create a "knob" child element for the background to represent the actual slide of the toggle.
               m_Knob = new();
               m_Knob.AddToClassList(inputKnobUssClassName);
               m_Input.Add(m_Knob);
   
               // There are three main ways to activate or deactivate the SlideToggle. All three event handlers use the
               // static function pattern described in the Custom control best practices.
   
               // ClickEvent fires when a sequence of pointer down and pointer up actions occurs.
               RegisterCallback<ClickEvent>(evt => OnClick(evt));
               // KeydownEvent fires when the field has focus and a user presses a key.
               RegisterCallback<KeyDownEvent>(evt => OnKeydownEvent(evt));
               // NavigationSubmitEvent detects input from keyboards, gamepads, or other devices at runtime.
               RegisterCallback<NavigationSubmitEvent>(evt => OnSubmit(evt));
           }
   
           static void OnClick(ClickEvent evt)
           {
               var slideToggle = evt.currentTarget as SlideToggle;
               slideToggle.ToggleValue();
   
               evt.StopPropagation();
           }
   
           static void OnSubmit(NavigationSubmitEvent evt)
           {
               var slideToggle = evt.currentTarget as SlideToggle;
               slideToggle.ToggleValue();
   
               evt.StopPropagation();
           }
   
           static void OnKeydownEvent(KeyDownEvent evt)
           {
               var slideToggle = evt.currentTarget as SlideToggle;
   
               // NavigationSubmitEvent event already covers keydown events at runtime, so this method shouldn't handle
               // them.
               if (slideToggle.panel?.contextType == ContextType.Player)
                   return;
   
               // Toggle the value only when the user presses Enter, Return, or Space.
               if (evt.keyCode == KeyCode.KeypadEnter || evt.keyCode == KeyCode.Return || evt.keyCode == KeyCode.Space)
               {
                   slideToggle.ToggleValue();
                   evt.StopPropagation();
               }
           }
   
           // All three callbacks call this method.
           void ToggleValue()
           {
               value = !value;
           }
   
           // Because ToggleValue() sets the value property, the BaseField class dispatches a ChangeEvent. This results in a
           // call to SetValueWithoutNotify(). This example uses it to style the toggle based on whether it's currently
           // enabled.
           public override void SetValueWithoutNotify(bool newValue)
           {
               base.SetValueWithoutNotify(newValue);
   
               //This line of code styles the input element to look enabled or disabled.
               m_Input.EnableInClassList(inputCheckedUssClassName, newValue);
           }
       }
   }
   

5. In the slide-toggle folder, create a USS file named SlideToggle.uss.

6. Open SlideToggle.uss in a text editor and replace its contents with the following:

   .slide-toggle__input {
       background-color: var(--unity-colors-slider_groove-background);
       max-width: 25px;
       border-top-left-radius: 8px;
       border-bottom-left-radius: 8px;
       border-top-right-radius: 8px;
       border-bottom-right-radius: 8px;
       overflow: visible;
       border-left-width: 1px;
       border-right-width: 1px;
       border-top-width: 1px;
       border-bottom-width: 1px;
       border-right-color: var(--unity-colors-slider_thumb-border);
       border-top-color: var(--unity-colors-slider_thumb-border);
       border-bottom-color: var(--unity-colors-slider_thumb-border);
       max-height: 16px;
       margin-top: 10px;
       border-left-color: var(--unity-colors-slider_thumb-border);
       transition-property: background-color;
       transition-duration: 0.5s;
   }
   
   .slide-toggle__input-knob {
       height: 16px;
       width: 16px;
       background-color: var(--unity-colors-slider_thumb-background);
       position: absolute;
       border-top-left-radius: 25px;
       border-bottom-left-radius: 25px;
       border-top-right-radius: 25px;
       border-bottom-right-radius: 25px;
       top: -1px;
       transition-property: translate, background-color;
       transition-duration: 0.5s, 0.5s;
       translate: -1px 0;
       border-left-width: 1px;
       border-right-width: 1px;
       border-top-width: 1px;
       border-bottom-width: 1px;
       border-left-color: var(--unity-colors-slider_thumb-border);
       border-right-color: var(--unity-colors-slider_thumb-border);
       border-top-color: var(--unity-colors-slider_thumb-border);
       border-bottom-color: var(--unity-colors-slider_thumb-border);
   }
   
   .slide-toggle__input--checked {
       background-color: rgb(0, 156, 10);
   }
   
   .slide-toggle__input--checked > .slide-toggle__input-knob {
       translate: 8px 0;
   }
   
   .slide-toggle:focus .slide-toggle__input-knob {
       border-left-width: 1px;
       border-right-width: 1px;
       border-top-width: 1px;
       border-bottom-width: 1px;
       border-left-color: var(--unity-colors-input_field-border-focus);
       border-right-color: var(--unity-colors-input_field-border-focus);
       border-top-color: var(--unity-colors-input_field-border-focus);
       border-bottom-color: var(--unity-colors-input_field-border-focus);
   }
   

Add a slide toggle to a UXML file with the UI Builder

1. In the slide-toggle folder, create a UI Document file named SlideToggleUsage.uxml.
2. Open SlideToggleUsage.uxml in the UI Builder.
3. In the UI Builder, select Library > Project > MyUILibrary.
4. Drag a SlideToggle into the Hierarchy window.
5. In the Inspector, enter a label text for your toggle in the Label field.
6. In the StyleSheets section, add SlideToggle.uss as existing USS.
7. Save and close the UI Builder.

Test the slide toggle

1. In the SampleScene, create a UI Document GameObject.
2. Select the UI Document, and drag SlideToggleUsage.uxml into the Source Asset field in the Inspector.
3. Enter play mode. You can click on the toggle, press Enter, press Return, or press Space and get it to flip back and forth.

其他资源

• Create custom controls
• Built-in Unity variables
• BEM standard