Building Flutter PullToRefresh in just 15 minutes

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.

Github Repository | @ShivamGoyal1899

ShivamGoyal1899/PullToRefresh
_A Flutter app featuring PullToRefresh. Contribute to ShivamGoyal1899/PullToRefresh development by creating an account …_github.com

Widget In Focus | RefreshIndicator

RefreshIndicator class - material library - Dart API
API docs for the RefreshIndicator class from the material library, for the Dart programming language. api.flutter.dev

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 and create a simple Flutter app **
Learn what is Flutter and how to set it up on Windows and Mac systems and get started with Flutter apps medium.com

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:

Building & running the application

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

The final output of the implementation

Enappd Store | Premium App Starters

Enappd | Ionic, React Native, Firebase themes, templates and starters
_Get the full source code for Ionic, React Native, Firebase mobile app templates and starters. Use free templates and …_store.enappd.com

More resources for Flutter