samples/web_embedding/ng-flutter

ng-flutter

This Angular project is a simple example of how Angular and Flutter web apps could be integrated, and have them interop.

Points of Interest

Angular

This repository is a quite standard Angular app. The following changes were made to be able to use (and interop) with a Flutter web application:

• package.json has a custom prebuild script that builds the Flutter web app, so Angular can find it later.
• flutter.js is added as a "scripts" entry in angular.json. Angular takes care of minimizing and injecting it as any other script.
• The rest of the flutter app flutter/build/web/ is registered as an "assets" entry in angular.json, and moved to /flutter.
• The ng-flutter component takes care of embedding Flutter web, and yielding control to Angular through an appLoaded EventEmitter. The object yielded by this emitter is a state controller exposed by flutter via a JS custom event!

Flutter

The embedded Flutter application lives in the flutter directory of this repo. That application is a standard web app, that doesn't need to be aware that it's going to be embedded in another framework.

• Flutter uses new @staticInterop methods to allow certain Dart functions to be called from JavaScript.
• Look at how createDartExport and broadcastAppEvent work together to make the _state controller of the Flutter app available to Angular!

How to build the app

Requirements

If you want to build and run this demo on your machine, you'll need a moderately recent version of Angular:

$ ng version

Angular CLI: 15.2.4
Node: 18.13.0
Package Manager: npm 9.4.2
OS: linux x64

And Flutter:

$ flutter --version

Flutter 3.10.0-12.0.pre.38 • channel master
Framework • revision 1a51dc2131 (8 days ago) • 2023-04-24 12:25:21 -0700
Engine • revision 5fbde6c0fc
Tools • Dart 3.1.0 (build 3.1.0-35.0.dev) • DevTools 2.23.1

Ensure npm, ng and flutter are present in your $PATH.

Building the app

This repository is a moderately standard Angular app. It integrates Flutter web by making it part of the Angular assets.

In order to build this app, first fetch its npm dependencies:

$ npm install

npm WARN deprecated @npmcli/move-file@2.0.1: This functionality has been moved to @npmcli/fs

added 963 packages, and audited 964 packages in 17s

93 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities

Then run the build script. It'll take care of building Flutter automatically:

$ npm run build

> ng-flutter@0.0.0 prebuild

... Flutter web build output ...

Compiling lib/main.dart for the Web...

> ng-flutter@0.0.0 build
> ng build

... Angular build output ...

✔ Browser application bundle generation complete.
✔ Copying assets complete.
✔ Index html generation complete.

Local Angular development

Once you've reached this point, you should be able to work with your Angular application normally, for example to run a local web server:

$ npm run start

> ng-flutter@0.0.0 start
> ng serve

✔ Browser application bundle generation complete.

Initial Chunk Files   | Names         |  Raw Size
vendor.js             | vendor        |   4.38 MB | 

... Angular build output...

** Angular Live Development Server is listening on localhost:4200, open your browser on http://localhost:4200/ **


✔ Compiled successfully.

Navigate to http://localhost:4200/. The application will automatically reload if you change any of its Angular source files.

Local Flutter web development

The Flutter app lives inside the flutter directory, and can be developed independently. Just do any changes on Flutter web as you'd normally do. It even includes a small web/index.html so you can see changes to your app without running the whole Angular setup.

Note For now, Angular does not auto-detect changes to your Flutter web app, so once you're happy with your Flutter web app, make sure to call npm run build so everything rebuilds and gets placed into its correct location.

Deploying the app

After npm run build, you should have a deployable Angular + Flutter web app in the dist directory of this Angular project.

Your built app can can be deployed anywhere, but do check Firebase hosting for a super-easy deployment experience!

Troubleshooting

Flutter

Ensure your flutter app is properly rebuilt after any changes.

• Run npm run build to re-build the Flutter app.

If you encounter error messages like:

Error: Can't resolve 'flutter/build/web/flutter.js' in '/my/checkout/of/ng-flutter'

You definitely need to run npm run build!

Reach out to the team(s)!

Have you had any problem not covered in this README? Do you want to see other embedding examples?

Let us know by creating an issue or opening a new pull request.

Thanks!