main.dart

import 'package:flutter/material.dart';
import 'dart:convert';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  static Widget widi = Container(
    color: Colors.black,
    height: 200,
    width: 100,
    child: Text('D'),
  );
  static Map<String, dynamic> map = {'widget': widi.toString()};
  static var jss = jsonEncode(map);
  static var jde = jsonDecode(jss);
  static String widgete = map['widget'];
  WidgetJson widgetJson = WidgetJson(widget: widgete);
  @override
  Widget build(BuildContext context) {
    print(jde);
    return Scaffold(
      appBar: AppBar(
        title: Text("Widget Title"),
      ),
      body: Stack(
        children: <Widget>[],
      ),
    );
  }
}

class WidgetJson {
  WidgetJson({this.widget});
  String widget;
}