ui基本完毕，修了一大把的bug

Assets/songsDatabase/loadDlcListPrefab.cs

@@ -7,7 +7,7 @@ public class loadDlcListPrefab : MonoBehaviour
 {
     private static readonly bool VerboseLogs = false;
     private const string RuntimeInstalledColumnName = "Installed DLC";
-    private const int DefaultFallbackDlcId = 66001;
+    private const int DefaultFallbackDlcId = 66002;
     private const string DlcSelectedIndexPrefsKey = "dlc_selected_index";
     [System.Serializable]
     public class Column
@@ -145,7 +145,19 @@ public class loadDlcListPrefab : MonoBehaviour
         }
 
         SongSelectUI.ForceFirstSongOnNextRestore = forceFirstSong;
-        targetButton.OnButtonClicked_ShowSongs();
+        // Restore is read-only: applying the selection here (including the
+        // fallback DLC) must not overwrite the user's genuine last choice.
+        // Select() runs synchronously inside OnButtonClicked_ShowSongs, so the
+        // suppression window only needs to span this call.
+        dlcButton.SuppressSelectionPersist = true;
+        try
+        {
+            targetButton.OnButtonClicked_ShowSongs();
+        }
+        finally
+        {
+            dlcButton.SuppressSelectionPersist = false;
+        }
 
         if (VerboseLogs)
         {
@@ -164,6 +176,20 @@ public class loadDlcListPrefab : MonoBehaviour
             return null;
         }
 
+        // Prefer restoring by the saved DLC id, which is stable across
+        // session-to-session ordering changes (e.g. runtime-installed DLCs).
+        int savedDlcId = PlayerPrefs.GetInt(dlcButton.SelectedDlcIdKey, 0);
+        if (savedDlcId > 0)
+        {
+            dlcButton savedById = FindButtonByDlcId(allButtons, savedDlcId);
+            if (savedById != null && HasSavedSongSelection(savedById))
+            {
+                forceFirstSong = false;
+                return savedById;
+            }
+        }
+
+        // Fall back to the saved positional index for legacy saves.
         int savedIndex = PlayerPrefs.GetInt(DlcSelectedIndexPrefsKey, 0);
         if (savedIndex >= 0 && savedIndex < allButtons.Length)
         {
@@ -221,14 +247,12 @@ public class loadDlcListPrefab : MonoBehaviour
             return false;
         }
 
+        // Only the songID key proves a genuine user click: SongButton.OnSongButtonClick
+        // always writes it alongside the index. The index key alone is unreliable because
+        // RestoreSelectedSongForCurrentDlc auto-writes it to 0 on mere display, so relying
+        // on it would treat any browsed-but-not-selected DLC as "user selected".
         string songIdKey = SongButton.BuildSongSelectedIdPrefsKey(dlcKey);
-        if (PlayerPrefs.HasKey(songIdKey) && PlayerPrefs.GetInt(songIdKey, 0) > 0)
-        {
-            return true;
-        }
-
-        string songIndexKey = SongButton.BuildSongSelectedIndexPrefsKey(dlcKey);
-        return PlayerPrefs.HasKey(songIndexKey);
+        return PlayerPrefs.HasKey(songIdKey) && PlayerPrefs.GetInt(songIdKey, 0) > 0;
     }
 
     private string BuildDlcKey(dlcButton button)
@@ -244,22 +268,8 @@ public class loadDlcListPrefab : MonoBehaviour
 
     private int GetDlcId(dlcButton button)
     {
-        if (button == null)
-        {
-            return 0;
-        }
-
-        if (button.dlcDataSO != null && button.dlcDataSO.dlcID > 0)
-        {
-            return button.dlcDataSO.dlcID;
-        }
-
-        if (button.dlcID != null && int.TryParse(button.dlcID.text, out int parsedId))
-        {
-            return parsedId;
-        }
-
-        return 0;
+        // Delegate to the button's own resolver to keep id resolution in one place.
+        return button != null ? button.ResolveOwnDlcId() : 0;
     }
 
     private List<Column> BuildDisplayColumns()