我从一个API登录，然后得到这个响应。现在我需要在通知图标中显示数组的计数。我在主页的应用程序栏中设置。我该如何实施？

{
    "user_id": 1,
    "user_name": "Mr Admin",
    "api_token": "6S3gRnPy55JKWyiOF7SwtYO12waZ8ozSyIHUNs2XSEcMh0DfTbpP5k51y2mL",
    "notifications": [
        {
            "id": "d54ee0cc-054a-4d51-a53b-5f6f658841ae",
            "type": "App\\Notifications\\HandSlipStatusNotification",
            "notifiable_id": 1,
            "notifiable_type": "App\\User",
            "data": {
                "payment_id": 471,
                "generate_payment_id": "10200471",
                "message": "Hand Slip Settled.",
                "amount": 850
            },
            "read_at": null,
            "created_at": "2020-10-12 15:50:38",
            "updated_at": "2020-10-12 15:50:38"
        },
        {
            "id": "aedb7880-4201-4805-b017-62242dfed741",
            "type": "App\\Notifications\\HandSlipStatusNotification",
            "notifiable_id": 1,
            "notifiable_type": "App\\User",
            "data": {
                "payment_id": 471,
                "generate_payment_id": "10200471",
                "message": "Hand Slip Disbursed.",
                "amount": 850
            },
            "read_at": null,
            "created_at": "2020-10-12 15:50:25",
            "updated_at": "2020-10-12 15:50:25"
        },
        {
            "id": "99b433b1-9432-44ae-a57f-fcb4ff92872f",
            "type": "App\\Notifications\\HandSlipStatusNotification",
            "notifiable_id": 1,
            "notifiable_type": "App\\User",
            "data": {
                "payment_id": 471,
                "generate_payment_id": "10200471",
                "message": "Hand Slip Approved.",
                "amount": 850
            },
            "read_at": null,
            "created_at": "2020-10-12 15:50:08",
            "updated_at": "2020-10-12 15:50:08"
        },

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login.dart

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

import '../sharePreference.dart';
import 'homepage.dart';

class Login extends StatefulWidget {
  @override
  _LoginState createState() => _LoginState();
}

class _LoginState extends State<Login> {

var notification ;
  bool isprocesscomplete = false;
  TextEditingController _userController = TextEditingController();
  TextEditingController _passwordController = TextEditingController();
  final _scaffoldKey = GlobalKey<ScaffoldState>();
  String BaseUrl = "my url";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      body: SingleChildScrollView(
        child: Center(
          child: Container(
            padding: EdgeInsets.fromLTRB(20, 100, 20, 20),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                Text(
                  "Login",
                  style: TextStyle(fontSize: 32),
                ),
                SizedBox(
                  height: 30,
                ),
                Card(
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(20),
                  ),
                  child: Container(
                    height: 220,
                    width: MediaQuery.of(context).size.width,
                    decoration: BoxDecoration(
                      borderRadius: BorderRadius.circular(20),
                    ),
                    child: Column(
                      children: [
                        Padding(
                          padding: const EdgeInsets.all(30),
                          child: TextField(
                            controller: _userController,
                            decoration: InputDecoration(hintText: "Username"),
                          ),
                        ),
                        Padding(
                          padding: const EdgeInsets.all(30),
                          child: TextField(
                            controller: _passwordController,
                            obscureText: true,
                            decoration: InputDecoration(hintText: "Password"),
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
                SizedBox(
                  height: 60,
                  width: MediaQuery.of(context).size.width,
                  child: RaisedButton(
                    color: Colors.lightBlue,
                    onPressed: () {
                      if (_userController.text == "" ||
                          _passwordController.text == "") {
                        final snackBar = SnackBar(
                            content: Text("Enter Username and Password"));
                        _scaffoldKey.currentState.showSnackBar(snackBar);
                      } else {
                        signIn(_userController.text, _passwordController.text);
                      }
                    },
                    child: ProgressButton(),
                    shape: RoundedRectangleBorder(
                      borderRadius: new BorderRadius.circular(16),
                    ),
                  ),
                ),
                SizedBox(
                  height: 20,
                ),
                FlatButton(
                  child: Text("Forgot password"),
                  onPressed: () {},
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }

  Widget ProgressButton() {
    if (isprocesscomplete != false) {
      return CircularProgressIndicator(
          valueColor: AlwaysStoppedAnimation<Color>(Colors.white));
    } else {
      return new Text(
        "Sign In",
        style: const TextStyle(
          color: Colors.white,
          fontSize: 15.0,
        ),
      );
    }
  }

  void signIn(String username, String password) async {
    setState(() {
      isprocesscomplete = true;
    });
    var response = await http.post(BaseUrl,
        headers: {"Content-Type": "application/json"},
        body: json.encode({
          "username": username,
          "password": password,
        }));

    Map<String, dynamic> value = json.decode(response.body);
    notification = value["notifications"];
    // print('Response ${response.body}');
    if (response.statusCode == 200) {
      try {
        ///You don't need it but it will be cool for show progress dialgo for 4 second then redirect even if we get reslut
        Future.delayed(Duration(seconds: 4), () {
          // 5s over make it false
          setState(() {
            isprocesscomplete = false;
          });
        });

        Map<String, dynamic> value = json.decode(response.body);

        print('Response ${response.body}');
        SharedPrefrence().setToken(value['api_token'].toString());
        SharedPrefrence().setName(value['user_name']);
        SharedPrefrence().setUserId(value['user_id'].toString());

        ///This is used when user loged in you can set this true,
        ///next time you open you need to check loginc in main.dart or splashscreen if this is true if it is true then
        ///redirect to home page it is false then redirect to Login page
        ///When you logout the app make sure you set this as false like "SharedPrefrence().setLoggedIn(false);"
        SharedPrefrence().setLoggedIn(true);

        ///Redirect to Home page
        Navigator.pushAndRemoveUntil(
                                context,
                                MaterialPageRoute(
                                    builder: (context) => HomePage(
                                      user_name: value['user_name'],
                                      api_token: value['api_token'],
                                        id : value['user_id'],
                                      notification: notification,

                                    )),
                                ModalRoute.withName("/login"));

      } catch (e) {
        e.toString();
        final snackBar =
        SnackBar(content: Text("something wrong,Try again 😑"));
        _scaffoldKey.currentState.showSnackBar(snackBar);
      }
    } else {
      var message = value['error'];
      final snackBar = SnackBar( backgroundColor: Colors.redAccent[700],
          content: Text(message.toString()));
      _scaffoldKey.currentState.showSnackBar(snackBar);
    }
  }
}

型
homepage.dart

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../sharePreference.dart';
import 'login.dart';
import 'login.dart';

class HomePage extends StatefulWidget {

  String user_name;
  final api_token;
  final id ;
 final  List<dynamic> notification ;
  // List data ;
  HomePage({ this.user_name, this.api_token , this.id, this.notification });

  @override
  _HomePageState createState() => _HomePageState();
}


class _HomePageState extends State<HomePage> {

  String nametoprint;
  String tokentoprint;

  @override
  void initState() {
    super.initState();
    Future name = SharedPrefrence().getName();
    name.then((data) async {
      nametoprint = data;
      print(nametoprint);
    });

    Future token= SharedPrefrence().getToken();
    token.then((data) async {
      tokentoprint= data;
      print(tokentoprint);
    });
  }


  int counter = 0;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text("Cash-Management"),
          backgroundColor: Colors.blue,
          actions: [

            new Stack(
              children: <Widget>[
                new IconButton(icon: Icon(Icons.notifications), onPressed: () {
                  setState(() {
                    counter = 0;
                  });
                }),
                counter != 0 ? new Positioned(
                  right: 11,
                  top: 11,
                  child: new Container(
                    padding: EdgeInsets.all(2),
                    decoration: new BoxDecoration(
                      color: Colors.red,
                      borderRadius: BorderRadius.circular(6),
                    ),
                    constraints: BoxConstraints(
                      minWidth: 14,
                      minHeight: 14,
                    ),
                    child: Text(
                      '$counter',
                      style: TextStyle(
                        color: Colors.white,
                        fontSize: 8,
                      ),
                      textAlign: TextAlign.center,
                    ),
                  ),
                ) : new Container()
              ],
            ),
            IconButton(
                icon: Icon(Icons.exit_to_app),
                onPressed: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(builder: (context) => Login()),
                  );
                }),
          ],
        ),
        body: ListView(
          children: <Widget>[
            Container(
              height: 200,
              child: Column(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
                  Text(
                    "${widget.user_name}",
                    // "  ${widget.username} ",
                    style: TextStyle(fontSize: 16),
                  ),
                  Text(
                    "${widget.api_token}",
                    // "  ${widget.username} ",
                    style: TextStyle(fontSize: 16),
                  ),
                  Text(
                    "${widget.id}",
                    // "  ${widget.username} ",
                    style: TextStyle(fontSize: 16),
                  ),
                  Text(" ${nametoprint} "),
                  Text("$nametoprint"),
                  Text("$tokentoprint"),
                ],
              ),
            ),

Container(
  color: Colors.blue,
  height: 300,
  child:   ListView.builder(
      itemCount: widget.notification == null ?  0 : widget.notification.length,
      itemBuilder: (context, index){
        return ListTile(
          title: Text(widget.notification[index] ["id"]),
          subtitle: Text(widget.notification[index]["type"]),

        );
      }),
),


          ],
        ),

        floatingActionButton: FloatingActionButton(onPressed: () {
          print("Increment Counter");
          setState(() {
            counter++;
          });
        }, child: Icon(Icons.add),),
      ),
    );
  }
}

型
我需要计算JSON中的数组，并需要在通知图标中显示计数。请用你的知识帮助我。