gistfile1.txt

class FamilyMember {
  String name;
  String userId;
  String fatherId;
  String fatherName;
  String alive;
  String sex;
  int generationNumber;

  FamilyMember(
      {this.name,
      this.userId,
      this.fatherId,
      this.fatherName,
      this.alive,
      this.sex,
      this.generationNumber});

  FamilyMember.fromJson(Map<String, dynamic> json) {
    name = json['name'];
    userId = json['user_id'];
    fatherId = json['father_id'];
    fatherName = json['father_name'];
    alive = json['alive'];
    sex = json['sex'];
    generationNumber = json['generation_number'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['name'] = this.name;
    data['user_id'] = this.userId;
    data['father_id'] = this.fatherId;
    data['father_name'] = this.fatherName;
    data['alive'] = this.alive;
    data['sex'] = this.sex;
    data['generation_number'] = this.generationNumber;
    return data;
  }
}

main.dart

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
import 'family-member-model.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.deepPurple,
      ),
      home: MyHomePage(title: 'Json Read and Search'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
   List<FamilyMember> familyMembers = [];

   //List<> myfamilyMembers = [];

  void getFamilyMembersList() {
        loadFamilyTreeJsonData();
   }
   
  @override
  void initState() {
    getFamilyMembersList();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return <Widget>[
            SliverAppBar(
              expandedHeight: 150.0,
              floating: false,
              pinned: true,
              flexibleSpace: FlexibleSpaceBar(
                  centerTitle: true,
                  title: Text("Collapsing Toolbar",
                      style: TextStyle(
                        color: Colors.white,
                        fontSize: 16.0,
                      )),
                  background: Image.network(
                    "https://images.pexels.com/photos/1616403/pexels-photo-1616403.jpeg?auto=compress&cs=tinysrgb&h=350",
                    fit: BoxFit.cover,
                  )
                  ),
            ),
          ];
        },
        body: ListView.builder(
              itemCount: familyMembers.length,
              itemBuilder: (buildContext, index) => _buildItem(index)
        ),
      ),
    );
  }


Widget _buildItem (index) {
    return  Center(
      child: Card(
        color: Colors.lightBlue,
        child: InkWell(
          splashColor: Colors.red.withAlpha(30),
          onTap: () {},
          child: Container(
            width: 300,
            height: 100,
            child: Center(child: Text(familyMembers[index].name)),
          ),
        ),
      ),
    );
}

  Future loadFamilyTreeJsonData() async {

   final jsonData = await DefaultAssetBundle.of(context).loadString('assets/sample.json');

  if (jsonData != null) { 
    final jsonResponse = jsonDecode(jsonData);
    
    print(jsonResponse.length);

   

    for (int i = 0; i < jsonResponse.length; i++) {
    familyMembers.add(FamilyMember.fromJson(jsonResponse[i]));
  }


    print(familyMembers);

    return familyMembers;

  } else {
    // If the server did not return a 200 OK response, then throw an exception.
    throw Exception('Failed to load album');
  }
}


}