Building a Chat Application Using Flutter

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If you are building a real-time chat application or messaging app, you want to reach as many users as possible whilst making the most efficient use of your available resources, so Flutter is an obvious choice, especially since it is easy to create high-quality and visually appealing apps with ease.

This article will explore the benefits of using Flutter for chat applications, including real-world examples, and discuss how PubNub's real-time messaging API can enhance your app's functionality. 

Why Build Chat Applications Using Flutter

Flutter allows developers to build natively compiled and visually appealing mobile, web, and desktop applications from a single codebase. It has become increasingly popular because of its versatility and ease of use. Like any language or framework, however, the choice of whether to use it is never black or white since there are both advantages and disadvantages:

Benefits of Using Flutter for Chat Applications

Most developers originally experiment with Flutter since it offers cross-platform compatibility, allowing you to create applications for multiple platforms from a single codebase.  This saves development time, reduces maintenance costs, and ensures a consistent user experience across all platforms.  Flutter’s hot reload capability enables rapid development time, allowing developers to see changes in their code almost instantly.  Hot reload significantly speeds up the development process and makes it easier to iterate when building your app.

Flutter offers an extensive library of pre-built widgets (plugins), which makes creating a visually appealing and highly responsive chat UI easy.  However, you are not limited to Flutter widgets, as the framework allows you to easily customize UI elements and create a unique look and feel for your chat application.

Finally, Flutter offers a strong support community that is active and growing.  Plenty of resources, tutorials, and packages are available to support your app development. 

Limitations to Using Flutter for Building Chat Applications

Whilst the benefits of using Flutter often outweigh the limitations, it is important to understand when Flutter might not be the best framework for your project.

Though the Flutter ecosystem is growing, there are still only a limited number of third-party libraries compared to more mature ecosystems and frameworks, especially native platforms such as Android, Firebase, iOS, cloud firestore, etc. 

Also, there will always be a fixed overhead for your application size with Flutter compared with native applications.  There are build and compiler settings you can adjust to reduce this overhead, but if application size is your primary concern or you are targeting users likely to have limited space on their devices, you should consider native development.

Despite these limitations, Flutter remains a compelling choice for building chat applications.

How to Build Flutter Chat Applications

At the highest level, the steps you follow to build a chat application using Flutter are as follows:

Flutter Chat Examples

Flutter is a very flexible language and you can create any type of chat application ranging from simple to more complex.  If you need some inspiration, here are some examples of what we have seen our customers create:

A Basic Text-based Chat App: A simple text-based chat app allows users to exchange text messages in real time. This app features a minimalistic UI with an input field and a message list. It can be built using the ListView and TextField widgets in Flutter and the PubNub real-time messaging service. Check out this web-based chat application tutorial for a step-by-step guide on building a similar chat app.

WhatsApp Clone: A more advanced example is a WhatsApp clone, which includes additional features like group chats, multimedia sharing, and end-to-end encryption. This app would require more complex UI components like TabBar, StreamBuilder, and StatefulWidgets. Additionally, you'll need to handle authentication, file uploads, and group management on the backend. You can find an example of a chat application for Android that incorporates some of these features.

Collaborative Editing App: A collaborative editing app is a more complex chat application that enables users to edit documents or code simultaneously. This type of app requires real-time synchronization of text edits, user cursors, and document changes. To build a collaborative editing app in Flutter, you'll need to use TextEditingController, ValueNotifier, and other advanced widgets and handle conflict resolution on the backend. For a deep dive into chat application architecture, you can refer to this article on chat application architecture explained.

Getting Started with PubNub for Your Flutter Chat App

PubNub is a real-time communication platform that provides APIs and infrastructure for real-time messaging, presence, message reactions, and other features. Integrating PubNub into your Flutter application is simple:

First, create a PubNub account and obtain your API keys.  This is free to do and you do not have to enter a credit card to generate your test keys.

Next, add PubNub to your project.  Flutter apps use the Dart programming language so you will use the PubNub Dart SDK.  Add the pubnub package to your pubspec.yaml file and import it into your Dart files.

dependencies:
  pubnub: ^4.2.2

Before communicating with the PubNub backend, you need to initialize the PubNub instance.  This is the step where you must also provide the API keys you previously generated.

import 'package:pubnub/pubnub.dart';
// createstate
void main() {
  final pubnub = PubNub(
    defaultKeyset: Keyset(
      subscribeKey: 'your_subscribe_key',
      publishKey: 'your_publish_key',
    ),
  );
}

To receive real-time messages, such as chat messages, you need to subscribe to a channel:

var subscription = pubnub.subscribe(channel: 'your_channel');

Once you have subscribed to a channel, you can then listen for and receive messages on that channel.  Use an event listener to receive incoming messages:

subscription.messages.listen((message) {
  print('Received message: ${message.content}');
});

To send a new message over PubNub, use the publish message method.

await pubnub.publish(
  channel: 'your_channel',
  message: {'content': 'Hello, world!'},
);

Create your application UI: Build your chat UI using widgets like MaterialApp, Scaffold, SizedBox, ListView, EdgeInsets, StatelessWidget, and TextStyle. For a more detailed guide on creating a chat UI, check out our article on chat services.

Authentication: You will need some way to authenticate your users, such as firebase_auth or google sign-in, then your application can track the currentuser in PubNub’s AppContext.

So, with minimal code, you can integrate PubNub into your Flutter chat app, giving you scalable client-to-client communication without building out your own infrastructure.  You are now set to build your real-time chat application with Flutter and PubNub. 

When you are ready to get started, we have a tutorial explaining how to build a simple Flutter chat app using our Dart SDK and our Dart SDK documentation.  These resources will also explain how to integrate push notifications into your app or connect to a real-time database.

If you are still researching, our chat developer path is a great jumping-off point to understand what resources are available for chat app developers.  Happy coding!