Thursday, 6 December 2018

Flutter Infinite ListView using Webservice


In this tutorial, we will see how to implement Infinite ListView in Flutter using webservice.



Here is the reference link i used most of the code but i used webservice in this tutorial.

Thanks to author of the tutorial
https://marcinszalek.pl/flutter/infinite-dynamic-listview/


Now Let see using this webservice
https://api.randomuser.me/?page=1&results=20&seed=abc

Here page number increments after scroll reaches the end.

Demo:
=======


main.dart
==========

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import 'package:akeepo/randomuser_infinitelist.dart';
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {


  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,

      ),
      home: InfiniteUsersList(),

   

    );
  }
}


randomuser_infinitelist.dart
=============================

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import 'dart:async';
import 'dart:convert';

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

class InfiniteUsersList extends StatefulWidget {
  static String tag = 'users-page';

  @override
  State<StatefulWidget> createState() {
    return new _InfiniteUsersListState();
  }
}

class _InfiniteUsersListState extends State<InfiniteUsersList> {
  List<User> users = new List<User>();
  ScrollController _scrollController = new ScrollController();
  bool isPerformingRequest = false;
  int pageNumber = 0;

  @override
  void initState() {
    super.initState();

    // Loading initial data or first request to get the data
    _getMoreData();

    // Loading data after scroll reaches end of the list
    _scrollController.addListener(() {
      if (_scrollController.position.pixels ==
          _scrollController.position.maxScrollExtent) {
        _getMoreData();
      }
    });
  }

  // to show progressbar while loading data in background
  Widget _buildProgressIndicator() {
    return new Padding(
      padding: const EdgeInsets.all(8.0),
      child: new Center(
        child: new Opacity(
          opacity: isPerformingRequest ? 1.0 : 0.0,
          child: new CircularProgressIndicator(),
        ),
      ),
    );
  }

  @override
  void dispose() {
    _scrollController.dispose();
    super.dispose();
  }

  // Webservice request to load 20 users data using paging
  Future<List<User>> _getUsers() async {
    List<User> users = new List<User>();
    setState(() {
      pageNumber++;
    });

    String url =
        "https://api.randomuser.me/?page=$pageNumber&results=20&seed=abc";
    print(url);

    var response = await http.get(url);
    var jsonData = json.decode(response.body);

    print(jsonData);

    var usersData = jsonData["results"];
    for (var user in usersData) {
      User newUser = User(user["name"]["first"] + user["name"]["last"],
          user["email"], user["picture"]["large"], user["phone"]);
      users.add(newUser);
    }

    return users;
  }

  _getMoreData() async {
    if (!isPerformingRequest) {
      setState(() {
        isPerformingRequest = true;
      });
      List<User> newEntries = await _getUsers(); //returns empty list
      if (newEntries.isEmpty) {
        double edge = 50.0;
        double offsetFromBottom = _scrollController.position.maxScrollExtent -
            _scrollController.position.pixels;
        if (offsetFromBottom < edge) {
          _scrollController.animateTo(
              _scrollController.offset - (edge - offsetFromBottom),
              duration: new Duration(milliseconds: 500),
              curve: Curves.easeOut);
        }
      }
      setState(() {
        users.addAll(newEntries);
        isPerformingRequest = false;
      });
    }
  }

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
          title: Text('Users',
              style:
                  TextStyle(color: Colors.white, fontWeight: FontWeight.bold))),
      body: Container(
          child: ListView.builder(
              shrinkWrap: true,
              controller: _scrollController,
              itemCount: users.length + 1,
              itemBuilder: (BuildContext context, int index) {
                if (index == users.length) {
                  return _buildProgressIndicator();
                } else {
                  return ListTile(
                    onTap: () {
                      Navigator.push(
                          context,
                          new MaterialPageRoute(
                              builder: (context) =>
                                  UserDetailPage(users[index])));
                    },
                    title: Text(users[index].fullName),
                    subtitle: Text(users[index].mobileNumber),
                    leading: CircleAvatar(
                        backgroundImage: NetworkImage(users[index].imageUrl)),
                  );
                }
              })),
    );
  }
}

class User {
  final String fullName;

  final String email;

  final String imageUrl;

  final String mobileNumber;

  User(this.fullName, this.email, this.imageUrl, this.mobileNumber);
}

// User Detail Page

class UserDetailPage extends StatelessWidget {
  final User user;

  UserDetailPage(this.user);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("User Details"),
      ),
      body: Center(
        child: Text(
          user.fullName,
          style: TextStyle(fontSize: 35.0),
        ),
      ),
    );
  }
}



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