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Beagle is an open source framework for multiplatform development using the concept of Server-Driven UI.

Beagle #

This is the library responsible for rendering a Beagle JSON in Flutter. It is currently in alpha stage, and most features are yet to be implemented. We welcome any help from the community in making improvements to the API - which isn't finished - and implementing features that are missing. At the end of this document you can find the session "State of development" where we show everything we have yet to do before releasing a stable version.

Versioning #

Every alpha and beta version of Beagle Flutter will follow the pattern 0.x.y, where x is the version of Beagle Web it's based on and y is every subsequent version where x would be the same.

In the version number, x refers to a version of the Beagle Web, because Beagle Flutter uses this lib under the hood.

Null safety compatibility #

For now, we'll not support null safety for the alpha versions, however this is a high priority implementation and should be available in future versions.

Installation #

  1. Open the file pubspec.yaml in the root of your project.
  2. Under dependencies, add beagle: ^0.9.4-alpha, or whatever the most recent version is.
  3. In your IDE (Android Studio or Visual Studio Code), click pub get. Or, from the terminal, type flutter pub get.

Usage #

It's quite simple to configure and use the Beagle Flutter library. Follow the steps bellow to be able to use it.

1. The configuration #

All the configuration necessary for Beagle to work is centered on the parameters of the BeagleSdk.init startup method. This params tells everything Beagle needs to know to render your widgets. Here we show only the basic options baseUrl and components. For a list of all the available options, please check the documentation for the Beagle Initialization.

2. Starting Beagle #

You can start Beagle at any point of the application. For this guide, we're going to start Beagle as soon as the app starts. For this, open the file lib/main.dart and import package:beagle/beagle.dart. After that, inside the main function, before rendering anything, call BeagleSdk.init passing the parameter previously informed. See the example below:

import 'package:beagle/beagle.dart';
import 'package:beagle_components/beagle_components.dart';

void main() {
  Map<String, ComponentBuilder> components = {
    'custom:loading': (element, _, __) {
      return Center(
        key: element.getKey(),
        child: const Text('My custom loading.'),

    baseUrl: '',
    components: components,
  // runApp();

3. Rendering a remote widget #

To render a Beagle Widget, you must use the component BeagleWidget which is provided by the Beagle Library. This widget requires a single parameter, the screenRequest, which specifies the request to fetch the first server-driven view of the flow. See the example below:

import 'package:beagle/beagle.dart';
import 'package:beagle_components/beagle_components.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

void main() {
    baseUrl: '',
    components: components,
  runApp(const BeagleSampleApp());

class BeagleSampleApp extends StatelessWidget {
  const BeagleSampleApp({Key key}) : super(key: key);

  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Beagle Sample',
      home: Scaffold(
        body: BeagleWidget(
          screenRequest: BeagleScreenRequest('welcome'),

Above, we used a simple Material App to render our first server-driven widget! The important part here is the component BeagleWidget, because it includes a remote view in the layout.

4. Implementing your own Beagle application #

This example showed how to render a simple example available in the web. For real use case scenarios, you'll have your own backend server providing the views - check the Beagle Backend Framework for more details. To make Beagle work with this backend, you only need to change the address in the field baseUrl of your configuration at BeagleSdk.init method.

If you're testing it in the Android emulator and using a local backend server, don't forget to use the ip To build a baseUrl that works for both the Android and iOS emulator, you can use Platform from dart:io:

import 'dart:io' show Platform;

final localhost = Platform.isAndroid ? '' : 'localhost';
final baseUrl = 'http://$localhost:8080';

Configuration options #

Beagle lets you configure a lot of its behavior. Please, check this article for a list of every option available.

The Beagle Widget #

The entry point for a Beagle remote view is the BeagleWidget. As mentioned before, it only requires a single parameter, the url of the view to render, but much more can be customized, e.g. observe requests and parsing errors rendering updates, make parametrized requests, etc. Check this doc for a list of every option accepted by the BeagleWidget.

Beagle services #

These are services that must be provided to Beagle for it to work properly. For now, we're embedding default implementations within the library. This is probably not going to be the case in the future, since it may represent potential security issues. The Beagle services are:

  • BeagleLogger: provides a logger for Beagle to use.
  • HttpClient: tells exactly how the network requests should be made, allowing custom headers and much more.
  • BeagleImageDownloader: allows a custom logic for downloading network images.
  • BeagleStorage: persists data across multiple executions by stating exactly how Beagle should store data.

You can set your own implementation of each of these services via BeagleSdk.init.

Customization #

Beagle is highly customizable because you can create your own components, actions and even operations. All of these must be provided when calling BeagleSdk.init.

  • Custom components: create your own components.
  • Custom actions: make the events in your components do exactly what you need.
  • Custom operations: if the operations shipped with Beagle are not enough for your expressions, create your own.
  • Design System: here you define all styles and local images that can be used by Beagle.

Other APIs #

  • Global context: allows manipulation of the global context in Beagle Flutter.
  • Analytics: gives information of every action executed, such as navigation data.
  • Renderer: sometimes it might be necessary to interact with Beagle while rendering a component or executing an action. This article shows how to use the Renderer API to achieve complex behaviors.

Current state of development #

Currently in alpha. It'll be moved to beta as soon as we have every layout tool (Yoga) working as expected. Here's a list of every feature we need to release a stable version of Beagle Flutter and its status.

It's important to reiterate that Beagle is an open source project and every help is welcomed!

Major features #

todo: check

Default actions #

todo: check

pub points


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Beagle is an open source framework for multiplatform development using the concept of Server-Driven UI.

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