1、清除其他人的画板

lib/components/white_board/white_board.dart

@@ -228,6 +228,7 @@ class _FWhiteBoardState extends State<FWhiteBoard> {
 
   void _clearUserLines(String userId) {
     myPen.clearCurrectUserLines(userId);
+    otherPen.clearCurrectUserLines(userId);
   }
 
   void _onPanCancel() {