修复问题：单选模式下多个日期被选中

去掉默认dispose会销毁数据，提供方法让用户手动销毁数据clearData

lib/controller.dart

@@ -502,6 +502,8 @@ class CalendarController {
     monthList.clear();
     weekList.clear();
     calendarProvider.clearData();
+    calendarConfiguration.weekChangeListeners=null;
+    calendarConfiguration.monthChangeListeners=null;
   }
 }
 

lib/widget/calendar_view.dart

@@ -69,7 +69,7 @@ class _CalendarViewWidgetState extends State<CalendarViewWidget> {
 
   @override
   void dispose() {
-    widget.calendarController.clearData();
+//    widget.calendarController.clearData();
     super.dispose();
   }
 

lib/widget/month_view.dart

@@ -162,12 +162,13 @@ class ItemContainerState extends State<ItemContainer> {
     dateModel = widget.dateModel;
     isSelected = ValueNotifier(dateModel.isSelected);
 
-    WidgetsBinding.instance.addPostFrameCallback((callback) {
-      if (configuration.selectMode == CalendarConstants.MODE_SINGLE_SELECT &&
-          dateModel.isSelected) {
-        calendarProvider.lastClickItemState = this;
-      }
-    });
+//    先注释掉这段代码
+//    WidgetsBinding.instance.addPostFrameCallback((callback) {
+//      if (configuration.selectMode == CalendarConstants.MODE_SINGLE_SELECT &&
+//          dateModel.isSelected) {
+//        calendarProvider.lastClickItemState = this;
+//      }
+//    });
   }
 
   /**