1.添加缓存清楚方法

lib/util/shared_prefe_util.dart

@@ -49,4 +49,9 @@ class SharedPreferencesUtil {
     }
     return defaultVal;
   }
+
+  static Future<bool> clean() async {
+    SharedPreferences prefs = await SharedPreferences.getInstance();
+    return  await prefs.clear();
+  }
 }