Unity 编辑器开发实战【Scene View】- UI Selector

        在Scene窗口编辑UI界面时，当重叠的UI元素较多时，很难点选想要选中的元素，UI Selector工具做了如下功能：右键时弹出一个列表，列举所有包含鼠标当前位置的RectTransform物体，在列表中选择即可选中该UI元素。

        实现该功能需要使用Scene View类，本人用的Unity版本是2020.3.16，该版本里显示onSceneGUIDelegate是弃用状态，使用duringSceneGui代替：

using UnityEngine;
using UnityEditor;

namespace SK.Framework
{
    [InitializeOnLoad]
    public static class UISelector
    {
        static UISelector()
        {
            SceneView.duringSceneGui += OnSceneGUI;
        }

        private static void OnSceneGUI(SceneView sceneView)
        {
           
        }
    }
}

        注意使用InitializeOnLoad属性，该属性应用的对象是静态构造函数，它可以保证在编辑器启动的时候调用该构造函数，因此我们在构造函数中使用SceneView类中的duringSceneGui来实现Scene窗口的自定义功能。

        首先我们想要在鼠标右键点击时弹出列表，在编辑器环境中的输入使用Event类，下面的代码表示鼠标右键抬起：

var ec = Event.current;
if (ec != null && ec.button == 1 && ec.type == EventType.MouseUp)
{

}

        列表中列举所有包含当前鼠标位置的Rect Transform，所以要先获取当前加载的场景中的所有Rect Transform组件：

private static void OnSceneGUI(SceneView sceneView)
{
    var ec = Event.current;
    if (ec != null && ec.button == 1 && ec.type == EventType.MouseUp)
    {
        ec.Use();

        var scenes = GetAllScenes();
        var groups = scenes
            .Where(m => m.isLoaded)
            .SelectMany(m => m.GetRootGameObjects())
            .Where(m => m.activeInHierarchy)
            .SelectMany(m => m.GetComponentsInChildren<RectTransform>())
        .GroupBy(m => m.gameObject.scene.name)
        .ToArray();
    }
}
private static IEnumerable<Scene> GetAllScenes()
{
    for (int i = 0; i < SceneManager.sceneCount; i++)
    {
        yield return SceneManager.GetSceneAt(i);
    }
}

        获取到所有的RectTransform组件后，判断哪些包含当前鼠标位置，通过Event.current中的mousePosition可以获得当前鼠标位置，但是需要注意，该坐标系中的原点为左上角：

        而UGUI中Canvas的坐标系以左下角为原点，因此需要先进行坐标转换，然后再通过Rect Transform Utility类中的RectangleContainsScreenPoint函数可以判断RectTransform是否包含指定位置：

using UnityEngine;
using UnityEditor;
using System.Linq;
using System.Collections.Generic;
using UnityEngine.SceneManagement;

namespace SK.Framework
{
    [InitializeOnLoad]
    public static class UISelector
    {
        static UISelector()
        {
            SceneView.duringSceneGui += OnSceneGUI;
        }

        private static void OnSceneGUI(SceneView sceneView)
        {
            var ec = Event.current;

            if (ec != null && ec.button == 1 && ec.type == EventType.MouseUp)
            {
                ec.Use();
                // 当前屏幕坐标，左上角是（0，0）右下角（camera.pixelWidth，camera.pixelHeight）
                Vector2 mousePosition = Event.current.mousePosition;
                // Retina 屏幕需要拉伸值
                float mult = EditorGUIUtility.pixelsPerPoint;
                // 转换成摄像机可接受的屏幕坐标，左下角是（0，0，0）右上角是（camera.pixelWidth，camera.pixelHeight，0）
                mousePosition.y = sceneView.camera.pixelHeight - mousePosition.y * mult;
                mousePosition.x *= mult;

                var scenes = GetAllScenes();
                var groups = scenes
                    .Where(m => m.isLoaded)
                    .SelectMany(m => m.GetRootGameObjects())
                    .Where(m => m.activeInHierarchy)
                    .SelectMany(m => m.GetComponentsInChildren<RectTransform>())
                    .Where(m => RectTransformUtility.RectangleContainsScreenPoint(m, mousePosition, sceneView.camera))
                .GroupBy(m => m.gameObject.scene.name)
                .ToArray();
            }
        }
        private static IEnumerable<Scene> GetAllScenes()
        {
            for (int i = 0; i < SceneManager.sceneCount; i++)
            {
                yield return SceneManager.GetSceneAt(i);
            }
        }
    }
}

同时还要处理同名UI元素问题，以及当前加载的场景可能不止一个的情况，如下：

        最终通过GenericMenu类实现右键菜单，通过Selection类中activeTransform和EditorGUI Utility类中PingObject实现选中，完整代码：

using UnityEngine;
using UnityEditor;
using System.Linq;
using System.Collections.Generic;
using UnityEngine.SceneManagement;

namespace SK.Framework
{
    [InitializeOnLoad]
    public static class UISelector
    {
        static UISelector()
        {
            SceneView.duringSceneGui += OnSceneGUI;
        }

        private static void OnSceneGUI(SceneView sceneView)
        {
            var ec = Event.current;

            if (ec != null && ec.button == 1 && ec.type == EventType.MouseUp)
            {
                ec.Use();
                // 当前屏幕坐标，左上角是（0，0）右下角（camera.pixelWidth，camera.pixelHeight）
                Vector2 mousePosition = Event.current.mousePosition;
                // Retina 屏幕需要拉伸值
                float mult = EditorGUIUtility.pixelsPerPoint;
                // 转换成摄像机可接受的屏幕坐标，左下角是（0，0，0）右上角是（camera.pixelWidth，camera.pixelHeight，0）
                mousePosition.y = sceneView.camera.pixelHeight - mousePosition.y * mult;
                mousePosition.x *= mult;

                var scenes = GetAllScenes();
                var groups = scenes
                    .Where(m => m.isLoaded)
                    .SelectMany(m => m.GetRootGameObjects())
                    .Where(m => m.activeInHierarchy)
                    .SelectMany(m => m.GetComponentsInChildren<RectTransform>())
                    .Where(m => RectTransformUtility.RectangleContainsScreenPoint(m, mousePosition, sceneView.camera))
                .GroupBy(m => m.gameObject.scene.name)
                .ToArray();
                var sceneCount = scenes.Count(m => m.isLoaded);
                var gc = new GenericMenu();
                var dic = new Dictionary<string, int>();
                foreach (var group in groups)
                {
                    foreach (var rt in group)
                    {
                        var name = rt.name;
                        var sceneName = rt.gameObject.scene.name;
                        var nameWithSceneName = sceneName + "/" + name;
                        var isContains = dic.ContainsKey(nameWithSceneName);
                        var text = sceneCount <= 1 ? name : nameWithSceneName;
                        if (isContains)
                        {
                            var count = dic[nameWithSceneName]++;
                            text += " [" + count.ToString() + "]";
                        }
                        var content = new GUIContent(text);
                        gc.AddItem(content, false, () =>
                        {
                            Selection.activeTransform = rt;
                            EditorGUIUtility.PingObject(rt.gameObject);
                        });
                        if (!isContains)
                        {
                            dic.Add(nameWithSceneName, 1);
                        }
                    }
                }
                gc.ShowAsContext();
            }
        }
        private static IEnumerable<Scene> GetAllScenes()
        {
            for (int i = 0; i < SceneManager.sceneCount; i++)
            {
                yield return SceneManager.GetSceneAt(i);
            }
        }
    }
}