Bind a custom control to custom data type

Version: 2021.3+

This example demonstrates how to bind custom controls to custom data types.

Example overview

This example creates a custom data type and a custom control based on three built-in controls. It binds the custom control to the custom data type. The drawer converts between Celsius and Fahrenheit.

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:

• UXML
• PropertyField

Create a custom data type

Create a custom data type Temperature, and use it as a serialized property.

1. Create a Unity project with any template.

2. Create a folder named bind-custom-data-type to store all the files.

3. Create a C# script named Temperature.cs and replace its contents with the following:

   using System;
   
   namespace UIToolkitExamples
   {
       public enum TemperatureUnit
       {
           Celsius,
           Farenheit
       }
   
       [Serializable]
       public struct Temperature
       {
           public double value;
           public TemperatureUnit unit;
       }
   }
   

4. Create a C# script named PlanetScript.cs and replace its contents with the following:

   using UnityEngine;
   
   namespace UIToolkitExamples
   {
       public class PlanetScript : MonoBehaviour
       {
           public Temperature coreTemperature;
       }
   }
   

Create a custom control

Create a custom Editor for Planet and a custom Property Drawer for Temperature.

In the custom Property Drawer, implement a button that converts temperature between Fahrenheit and Celsius by writing to properties of SerializedProperty (use doubleValue and enumValueIndex) and then calling SerializedObject.ApplyModifiedProperties().

The custom Property Draweris is considered as a custom control. It’s a built-in control that behaves in a custom way.

1. Create a folder named Editor.

2. In the Editor folder, create a C# script named PlanetEditor.cs and replace its contents with the following:

   using UnityEditor;
   using UnityEngine.UIElements;
   using UnityEditor.UIElements;
   
   namespace UIToolkitExamples
   {
       [CustomEditor(typeof(PlanetScript))]
       public class PlanetEditor : Editor
       {
           public override VisualElement CreateInspectorGUI()
           {
               return new PropertyField(serializedObject.FindProperty("coreTemperature"));
           }
       }
   }
   

3. In the Editor folder, create a C# script named TemperatureDrawer.cs and replace its contents with the following:

   using UnityEditor;
   using UnityEngine;
   using UnityEngine.UIElements;
   
   namespace UIToolkitExamples
   {
       [CustomPropertyDrawer(typeof(Temperature))]
       public class TemperatureDrawer : PropertyDrawer
       {
           public override VisualElement CreatePropertyGUI(SerializedProperty property)
           {
               var asset = Resources.Load<VisualTreeAsset>("temperature_drawer");
               var drawer = asset.Instantiate(property.propertyPath);
   
               drawer.Q<Label>().text = property.displayName;
   
               // Don't allow conversion when you've selected multiple objects in the Inspector
               if (!property.serializedObject.isEditingMultipleObjects)
               {
                   drawer.Q<Button>().RegisterCallback<ClickEvent, SerializedProperty>(Convert, property);
               }
   
               return drawer;
           }
   
           static void Convert(ClickEvent evt, SerializedProperty property)
           {
               var valueProperty = property.FindPropertyRelative("value");
               var unitProperty = property.FindPropertyRelative("unit");
   
               // F -> C
               if (unitProperty.enumValueIndex == (int)TemperatureUnit.Farenheit)
               {
                   valueProperty.doubleValue -= 32;
                   valueProperty.doubleValue *= 5.0d / 9.0d;
                   unitProperty.enumValueIndex = (int)TemperatureUnit.Celsius;
               }
               else // C -> F
               {
                   valueProperty.doubleValue *= 9.0d / 5.0d;
                   valueProperty.doubleValue += 32;
                   unitProperty.enumValueIndex = (int)TemperatureUnit.Farenheit;
               }
   
               // Important: Because you are bypassing the binding system, you must save the modified SerializedObject
               property.serializedObject.ApplyModifiedProperties();
           }
       }
   }
   

Set the binding

Create a UXML file with the following:

• A DoubleField
• An EnumField
• A Button

Set the binding-path of the two fields to value and unit of the Temperature property.

1. In the Editor folder, create a folder named Resources.

2. In the Resources folder, create a UI Document named temperature_drawer.uxml and replace its contents with 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">
       <ui:VisualElement class="unity-base-field">
           <ui:Label class="unity-base-field__label" />
           <ui:VisualElement class="unity-base-field__input" style="flex-direction: row;">
               <uie:DoubleField binding-path="value" />
               <uie:EnumField binding-path="unit" />
               <ui:Button text="Convert" />
           </ui:VisualElement>
       </ui:VisualElement>
   </ui:UXML>
   

Test the binding

1. Create an empty GameObject in a scene.
2. In the Hierarchy, select the GameObject.
3. Drag PlanetScript.cs to the Inspector. This adds a Planet Script component to the GameObject.
4. Enter a number in the Temperature field and select a unit from the dropdown.
5. Select the Convert button to convert between units. If you make changes in the Inspector UI, the Temperature property of the custom contol changes.

其他资源

• SerializedObject data binding
• Bindable elements
• Binding data type conversion
• Implementation details
• Binding examples