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创建拖放式 UI 以在编辑器窗口之间拖动

此示例演示如何使用用户界面
Toolkit 的拖动事件以及 UnityEditor.DragAndDrop 类，用于在窗口之间启用拖放 UI。

示例概述

该示例创建两个自定义编辑器窗口。您可以从项目窗口
进入编辑器窗口。您还可以将同一资源从一个窗口拖动到另一个窗口。

您可以在此示例创建的完整文件此 GitHub 存储库中找到

先决条件

本指南适用于熟悉 Unity 编辑器、UI 工具包和 C# 脚本的开发人员。在开始之前，请熟悉以下内容：

• 用户界面生成器
• USS
• 用户体验
• 使用操纵器处理事件
• 拖放事件
• 指针事件
• UnityEditor.DragAndDrop

定义编辑器窗口的内容

使用内置的 UXML 文件中定义每个编辑器窗口的内容视觉元素
.每个编辑器窗口都包含背景、标题、放置区域和文本。设置 USS 文件中的可视元素的样式。

1. 使用任何模板创建 Unity 项目。
2. 创建一个名为存储所有文件的文件夹。drag-and-drop-across-window

创建以以下内容命名的 UI 文档：DragAndDrop.uxml

<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="background">
        <ui:VisualElement class="header">
            <ui:Label text="Drag And Drop Sample" display-tooltip-when-elided="true" class="header__label" />
        </ui:VisualElement>
        <ui:VisualElement class="drop-area">
            <ui:Label text="Drag an asset here..." display-tooltip-when-elided="true" class="drop-area__label" />
        </ui:VisualElement>
    </ui:VisualElement>
</ui:UXML>

4. 创建以以下内容命名的样式表：DragAndDrop.uss

.background {
    flex-grow: 1;
    background-color: rgba(30, 30, 30, 255);
}

.header {
    align-items: center;
    margin-left: 10px;
    margin-right: 10px;
    margin-top: 10px;
    margin-bottom: 10px;
    padding-left: 5px;
    padding-right: 5px;
    padding-top: 5px;
    padding-bottom: 5px;
    background-color: rgba(112, 128, 144, 255);
    border-left-color: rgba(211, 211, 211, 255);
    border-right-color: rgba(211, 211, 211, 255);
    border-top-color: rgba(211, 211, 211, 255);
    border-bottom-color: rgba(211, 211, 211, 255);
    border-left-width: 2px;
    border-right-width: 2px;
    border-top-width: 2px;
    border-bottom-width: 2px;
}

.header__label {
    font-size: 18px;
    color: rgba(255, 255, 255, 255);
}

.drop-area {
    flex-grow: 1;
    align-items: center;
    justify-content: center;
    margin-left: 10px;
    margin-right: 10px;
    margin-top: 10px;
    margin-bottom: 10px;
    padding-left: 5px;
    padding-right: 5px;
    padding-top: 5px;
    padding-bottom: 5px;
    background-color: rgba(112, 128, 144, 255);
    border-left-color: rgba(211, 211, 211, 255);
    border-right-color: rgba(211, 211, 211, 255);
    border-top-color: rgba(211, 211, 211, 255);
    border-bottom-color: rgba(211, 211, 211, 255);
    border-left-width: 2px;
    border-right-width: 2px;
    border-top-width: 2px;
    border-bottom-width: 2px;
    border-top-left-radius: 20px;
    border-bottom-left-radius: 20px;
    border-top-right-radius: 20px;
    border-bottom-right-radius: 20px;
}

.drop-area--dropping {
    opacity: 0.4;
    background-color: rgba(0, 100, 0, 255);
}

.drop-area__label {
    -unity-font-style: italic;
    color: rgba(255, 255, 255, 255);
}

5. 双击以在 UI 生成器中将其打开。DragAndDrop.xml

6. 添加为现有 USS。DragAndDrop.uss

创建操纵器以存储事件回调

操纵器是注册和取消注册与输入相关的事件回调的对象。在 C# 脚本中创建自定义操纵器，以注册指针事件并为编辑器窗口拖动事件。

1. 在该文件夹中，创建一个名为 的文件夹。drag-and-drop-across-windowEditor

在该文件夹中，创建一个以以下内容命名的 C# 文件：EditorDragAndDropManipulator.cs

using UnityEngine;
using UnityEditor;
using UnityEngine.UIElements;

namespace Samples.Editor.General
{
    // The DragAndDropManipulator class is a private class within DragAndDropWindow.
    public partial class DragAndDropWindow
    {
        // DragAndDropManipulator is a manipulator that stores pointer-related callbacks, so it inherits from
        // PointerManipulator.
        class DragAndDropManipulator : PointerManipulator
        {
            // The Label in the window that shows the stored asset, if any.
            Label dropLabel;
            // The stored asset object, if any.
            Object droppedObject = null;
            // The path of the stored asset, or the empty string if there isn't one.
            string assetPath = string.Empty;

            public DragAndDropManipulator(VisualElement root)
            {
                // The target of the manipulator, the object to which to register all callbacks, is the drop area.
                target = root.Q<VisualElement>(className: "drop-area");
                dropLabel = root.Q<Label>(className: "drop-area__label");
            }

            protected override void RegisterCallbacksOnTarget()
            {
                // Register a callback when the user presses the pointer down.
                target.RegisterCallback<PointerDownEvent>(OnPointerDown);
                // Register callbacks for various stages in the drag process.
                target.RegisterCallback<DragEnterEvent>(OnDragEnter);
                target.RegisterCallback<DragLeaveEvent>(OnDragLeave);
                target.RegisterCallback<DragUpdatedEvent>(OnDragUpdate);
                target.RegisterCallback<DragPerformEvent>(OnDragPerform);
            }

            protected override void UnregisterCallbacksFromTarget()
            {
                // Unregister all callbacks that you registered in RegisterCallbacksOnTarget().
                target.UnregisterCallback<PointerDownEvent>(OnPointerDown);
                target.UnregisterCallback<DragEnterEvent>(OnDragEnter);
                target.UnregisterCallback<DragLeaveEvent>(OnDragLeave);
                target.UnregisterCallback<DragUpdatedEvent>(OnDragUpdate);
                target.UnregisterCallback<DragPerformEvent>(OnDragPerform);
            }

            // This method runs when a user presses a pointer down on the drop area.
            void OnPointerDown(PointerDownEvent _)
            {
                // Only do something if the window currently has a reference to an asset object.
                if (droppedObject != null)
                {
                    // Clear existing data in DragAndDrop class.
                    DragAndDrop.PrepareStartDrag();

                    // Store reference to object and path to object in DragAndDrop static fields.
                    DragAndDrop.objectReferences = new[] { droppedObject };
                    if (assetPath != string.Empty)
                    {
                        DragAndDrop.paths = new[] { assetPath };
                    }
                    else
                    {
                        DragAndDrop.paths = new string[] { };
                    }

                    // Start a drag.
                    DragAndDrop.StartDrag(string.Empty);
                }
            }

            // This method runs if a user brings the pointer over the target while a drag is in progress.
            void OnDragEnter(DragEnterEvent _)
            {
                // Get the name of the object the user is dragging.
                var draggedName = string.Empty;
                if (DragAndDrop.paths.Length > 0)
                {
                    assetPath = DragAndDrop.paths[0];
                    var splitPath = assetPath.Split('/');
                    draggedName = splitPath[splitPath.Length - 1];
                }
                else if (DragAndDrop.objectReferences.Length > 0)
                {
                    draggedName = DragAndDrop.objectReferences[0].name;
                }

                // Change the appearance of the drop area if the user drags something over the drop area and holds it
                // there.
                dropLabel.text = $"Dropping '{draggedName}'...";
                target.AddToClassList("drop-area--dropping");
            }

            // This method runs if a user makes the pointer leave the bounds of the target while a drag is in progress.
            void OnDragLeave(DragLeaveEvent _)
            {
                assetPath = string.Empty;
                droppedObject = null;
                dropLabel.text = "Drag an asset here...";
                target.RemoveFromClassList("drop-area--dropping");
            }

            // This method runs every frame while a drag is in progress.
            void OnDragUpdate(DragUpdatedEvent _)
            {
                DragAndDrop.visualMode = DragAndDropVisualMode.Generic;
            }

            // This method runs when a user drops a dragged object onto the target.
            void OnDragPerform(DragPerformEvent _)
            {
                // Set droppedObject and draggedName fields to refer to dragged object.
                droppedObject = DragAndDrop.objectReferences[0];
                string draggedName;
                if (assetPath != string.Empty)
                {
                    var splitPath = assetPath.Split('/');
                    draggedName = splitPath[splitPath.Length - 1];
                }
                else
                {
                    draggedName = droppedObject.name;
                }

                // Visually update target to indicate that it now stores an asset.
                dropLabel.text = $"Containing '{draggedName}'...\n\n" *
                    $"(You can also drag from here)";
                target.RemoveFromClassList("drop-area--dropping");
            }
        }
    }
}

创建编辑器窗口并实例化操纵器

在 C# 脚本中创建两个自定义编辑器窗口，并为每个编辑器窗口实例化一个操纵器。

创建一个以以下内容命名的 C# 文件：DragAndDropWindow.cs

using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;

namespace Samples.Editor.General
{
    public partial class DragAndDropWindow : EditorWindow
    {
        // This is the visual tree that contains the UI structure of the window.
        [SerializeField]
        VisualTreeAsset uxmlAsset;

        // This manipulator contains all of the event logic for this window.
        DragAndDropManipulator manipulator;

        // This is the minimum size of both windows.
        readonly static Vector2 windowMinSize = new(300, 180);

        // These are the starting positions of the windows.
        readonly static Vector2 windowAPosition = new(50, 50);
        readonly static Vector2 windowBPosition = new(450, 100);

        // These are the titles of the windows.
        const string windowATitle = "Drag and Drop A";
        const string windowBTitle = "Drag and Drop B";

        // This method opens two DragAndDropWindows when a user selects the specified menu item.
        [MenuItem("Window/UI Toolkit/Drag And Drop (Editor)")]
        public static void OpenDragAndDropWindows()
        {
            // Create the windows.
            var windowA = CreateInstance<DragAndDropWindow>();
            var windowB = CreateInstance<DragAndDropWindow>();

            // Define the attributes of the windows and display them.
            windowA.minSize = windowMinSize;
            windowB.minSize = windowMinSize;
            windowA.Show();
            windowB.Show();
            windowA.titleContent = new(windowATitle);
            windowB.titleContent = new(windowBTitle);
            windowA.position = new(windowAPosition, windowMinSize);
            windowB.position = new(windowBPosition, windowMinSize);
        }

        void OnEnable()
        {
            if (uxmlAsset != null)
            {
                uxmlAsset.CloneTree(rootVisualElement);
            }

            // Instantiate manipulator.
            manipulator = new(rootVisualElement);
        }

        void OnDisable()
        {
            // The RemoveManipulator() method calls the Manipulator's UnregisterCallbacksFromTarget() method.
            manipulator.target.RemoveManipulator(manipulator);
        }
    }
}

2. 在“项目”窗口中，选择并拖动到 Uxml 资源DragAndDropWindow.csDragAndDrop.xml检查员。

3. 从菜单中选择“窗口> UI 工具包”>“拖放（编辑器）”。打开两个拖放窗口。您可以将资源从“项目”窗口拖动到这些窗口中的放置区域。您还可以将同一资源从一个窗口拖动到另一个窗口。

由3D建模学习工作室整理翻译，转载请注明出处！

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