fix(fix-system): 修复拖拽 UI 跳位

Co-authored-by: Cursor <cursoragent@cursor.com>

Assets/Scripts/FixSystem/DraggableUI.cs

@@ -8,6 +8,8 @@ public class DraggableUI : MonoBehaviour, IDragHandler, IPointerDownHandler
     public RectTransform target;
     public Button button;
     private bool isLocked = false;
+    private Vector3 _dragOffset;
+    private float _dragScreenZ;
 
     private void Awake()
     {
@@ -16,22 +18,34 @@ public class DraggableUI : MonoBehaviour, IDragHandler, IPointerDownHandler
 
     public void OnPointerDown(PointerEventData eventData)
     {
-        // 这里可以添加按下时的逻辑，比如记录初始位置
+        if (isLocked) return;
+
+        Camera cam = ResolveCamera(eventData);
+        if (cam == null) return;
+
+        // 记录指针与物体的世界空间偏移，避免拖动开始时物体跳到指针中心。
+        _dragScreenZ = cam.WorldToScreenPoint(transform.position).z;
+        Vector3 pointerWorld = ScreenToWorld(cam, eventData.position, _dragScreenZ);
+        _dragOffset = transform.position - pointerWorld;
     }
 
     public void OnDrag(PointerEventData eventData)
     {
         if (isLocked) return;
 
-        Vector3 screenPosition = new Vector3(eventData.position.x, eventData.position.y,
-        Camera.main.WorldToScreenPoint(transform.position).z);
-        Vector3 move = Camera.main.ScreenToWorldPoint(screenPosition);
+        Camera cam = ResolveCamera(eventData);
+        if (cam == null) return;
+
+        Vector3 pointerWorld = ScreenToWorld(cam, eventData.position, _dragScreenZ);
+        Vector3 move = pointerWorld + _dragOffset;
         move.z = transform.position.z;
         transform.position = move;
     }
 
     void Update()
     {
+        if (target == null || button == null) return;
+
         float distance = Vector3.Distance(transform.position, target.position);
 
         if (distance <= 1 && !isLocked)
@@ -53,4 +67,16 @@ public class DraggableUI : MonoBehaviour, IDragHandler, IPointerDownHandler
     {
         isLocked = false;
     }
-}
+
+    private static Camera ResolveCamera(PointerEventData eventData)
+    {
+        if (eventData != null && eventData.pressEventCamera != null)
+            return eventData.pressEventCamera;
+        return Camera.main;
+    }
+
+    private static Vector3 ScreenToWorld(Camera cam, Vector2 screenPosition, float screenZ)
+    {
+        return cam.ScreenToWorldPoint(new Vector3(screenPosition.x, screenPosition.y, screenZ));
+    }
+}