优化和重构Theme，解决引用相同或丢失的问题 #118

Editor/Utility/ThemeCheck.cs

@@ -0,0 +1,60 @@
+using UnityEditor;
+using UnityEngine;
+
+namespace XCharts
+{
+    internal static class ThemeCheck
+    {
+        public class ThemeAssetPostprocessor : AssetPostprocessor
+        {
+            static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets,
+                string[] movedFromAssetsPaths)
+            {
+                foreach (var assetPath in importedAssets)
+                {
+                    CheckAddedAsset(assetPath);
+                }
+                foreach (var assetPath in deletedAssets)
+                {
+                    CheckDeletedAsset(assetPath);
+                }
+            }
+        }
+
+        public static void CheckAddedAsset(string assetPath)
+        {
+            if (!IsThemeAsset(assetPath)) return;
+            var obj = AssetDatabase.LoadAssetAtPath<TextAsset>(assetPath);
+            if (XChartsSettings.AddJsonTheme(obj))
+            {
+                XThemeMgr.ReloadThemeList();
+            }
+        }
+
+        public static void CheckDeletedAsset(string assetPath)
+        {
+            if (!IsThemeAsset(assetPath)) return;
+            var themes = XChartsSettings.customThemes;
+            var changed = false;
+
+            for (int i = themes.Count - 1; i >= 0; i--)
+            {
+                if (themes[i] == null)
+                {
+                    themes.RemoveAt(i);
+                    changed = true;
+                }
+            }
+            if (changed)
+            {
+                XThemeMgr.ReloadThemeList();
+            }
+        }
+
+        private static bool IsThemeAsset(string assetPath)
+        {
+            if (!assetPath.EndsWith(".json")) return false;
+            return true;
+        }
+    }
+}