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Building Flutter PullToRefresh in just 15 minutes

Learn easy implementation of a PullToRefresh gesture in Flutter.

Introduction

The pull-to-refresh pattern lets a user pull down on a list of data using touch in order to retrieve more data. The "Pull-to-refresh" gesture was first introduced by Loren Brichter in the Tweetie app and in no time it became so popular that countless apps adopted this gesture. Today "pull-to-refresh" feature is a natural part of many popular apps, including Twitter, Gmail, Tweetbot and others.

What you'll build?

In this tutorial, you'll build a mobile app featuring a PullToRefresh gesture using the Flutter SDK. Your app will:

  • Display a dynamic list with a random number of items
  • Each time you PullToRefresh the no of items will change in the list

That's how our PullToRefresh gonna work

This tutorial focuses on adding a PullToRefresh gesture to a Flutter app. Non-relevant concepts and code blocks are glossed over and are provided for you to simply copy and paste.


Setting up Flutter on your machine

The detailed steps to install Flutter on your personal computer & getting started with Flutter is available at the following blog

How to install Flutter on Mac & Windows

Coding the component

Component Syntax

The basic format of PullToRefresh gesture looks like the one below:

const RefreshIndicator({
      Key key,
      @required Widget child,
      double displacement: 40.0,
      @required RefreshCallback onRefresh,
      Color color,
      Color backgroundColor,
      ScrollNotificationPredicate
          notificationPredicate: defaultScrollNotificationPredicate,
      String semanticsLabel,
      String semanticsValue
})

Implementation

The most generic way to implement PullToRefresh is as follows:

const RefreshIndicator({
  Key key,
  @required this.child,
  this.displacement = 40.0,
  @required this.onRefresh,
  this.color,
  this.backgroundColor,
  this.notificationPredicate = defaultScrollNotificationPredicate,
  this.semanticsLabel,
  this.semanticsValue,
}) : assert(child != null),
     assert(onRefresh != null),
     assert(notificationPredicate != null),
     super(key: key);

Importing dart libraries to main.dart file

Import dart:async & dart:math libraries to your main.dart file by adding the following line at the starting of the file:

import 'dart:async';
import 'dart:math';

Putting Code in action

Amend your main.dart file as per the following code:

import 'dart:async';
import 'dart:math';
import 'package:flutter/material.dart';

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

class PullToRefresh extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Pull To Refresh',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  var list;
  var random;

  var refreshKey = GlobalKey<RefreshIndicatorState>();

  @override
  void initState() {
    list = List.generate(3, (i) => "Item $i");
    super.initState();
    random = Random();
    refreshList();
  }

  Future<Null> refreshList() async {
    refreshKey.currentState?.show(atTop: false);
    await Future.delayed(Duration(seconds: 2));

    setState(() {
      list = List.generate(random.nextInt(10), (i) => "Item $i");
    });

    return null;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Pull to refresh"),
      ),
      body: RefreshIndicator(
        key: refreshKey,
        child: ListView.builder(
          itemCount: list?.length,
          itemBuilder: (context, i) => ListTile(
            title: Text(list[i]),
          ),
        ),
        onRefresh: refreshList,
      ),
    );
  }
}

Building & running the application

  • Connect your Emulator or physical Android device to test the application.
  • Click on Build & Run.
  • And Boooom πŸ’₯, your app is ready.
    The final build would look like the below illustration.

The final output of the implementation


❓ Queries / Bugs

If you got any queries or found a bug, open an Issue or ping me over on hi@itsshivam.com

πŸ“ License

Licensed under the MIT License.

πŸ’œ Thanks

Thanks to all contributors and to sponsors for supporting the project.

Buy Me A Coffee Become a Patron! Pay with PayPal!

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πŸ”„ A Flutter app featuring PullToRefresh

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