This is a guest post authored by Daniel Llewellyn. It originally featured on his blog, we’re reproducing it here with Dan’s permission. Dan is an active member of the WordPress, WSL, Ubuntu and Snapcraft communities. Thanks Dan!
Recently there was an announcement from Ubuntu that the desktop team are working on a replacement for the Ubiquity installer. The really interesting part of the post by Martin Wimpress, head of the Ubuntu Desktop team at Canonical, is that the new installer will be built using Flutter.
Flutter is a cross-platform User Interface framework that can target Linux, macOS, Windows, Android, and iOS all from the same source code. I have been aware of Flutter for some time now but have been trepidation in jumping in to sample the water, because I am completely unfamiliar with the Dart programming language and was worried about making the time investment.
With the news from Ubuntu I decided that now is a good time to get my feet wet and find out what this new shiny is all about. To that end, I have installed Flutter and managed to get the sample application running on Ubuntu! There were a few gotchas, however, so below I’ve summarised the important steps to get a fully functional toolchain set up:
First up, we install the Flutter Snap Package. Run:
sudo snap install flutter --classic
By default this will install the commands:
We can reduce the typing required to call
dart, along with reducing the cognitive load when translating any instructions that do not expect the
flutter. prefix. Run the following to map
flutter.dart to the name
dart so you can call it without the prefix:
sudo snap alias flutter.dart dart
Next, we need the Android Studio. The instructions supplied by Google require you to download and extract a
.tar.gz file to a place of your choosing. That’s too much work. Instead, install the community-maintained Snap Package with:
sudo snap install android-studio --classic
Find the Android Studio icon in your desktop applications menu, such as the dash in Gnome or the K menu in KDE, or execute in the terminal:
Run through the first-install wizard accepting all the defaults. We won’t be using Android Studio for anything other than its ability to maintain the Android SDK and emulators.
Now, flutter needs to know the location of our Android Studio snap, or you will be unable to build an app even if you’re not targetting Android, so run:
flutter config --android-studio-dir /snap/android-studio/current/android-studio
We need to accept the Android licenses to use Flutter, so run:
flutter doctor --android-licenses
Read through each license it presents (you’re gonna read them, right?) and accept them with a
Y keypress followed by enter when prompted.
If you are likely to be developing for Linux, macOS, or Windows in your Flutter projects, you need to update to the dev branch of Flutter and enable each toolchain. Run:
# switch to dev branch flutter channel dev # update Flutter to the latest dev branch revision flutter upgrade # enable Linux toolchain flutter config --enable-linux-desktop # enable macOS toolchain flutter config --enable-macos-desktop # enable Windows toolchain flutter config --enable-windows-desktop
Note: while you can set-up your project for macOS and Windows support you must use those operating systems to actually build an app targeting each.
Finally, we check that everything is correctly set-up. Run:
If everything is good, it’ll output similar to below:
Doctor summary (to see all details, run flutter doctor -v): [✓] Flutter (Channel dev, 1.26.0-17.1.pre, on Linux, locale en_GB.UTF-8) [✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3) [✓] Chrome - develop for the web [✓] Linux toolchain - develop for Linux desktop [✓] Android Studio [✓] Connected device (2 available) • No issues found!
Testing Flutter by building a sample
Create a new directory to hold our sample app. Run:
mkdir flutter_example cd flutter_example
The name used for the folder is also used by Dart to form the package ID. Unfortunately, that means we can only use alphanumeric characters and the underscore character. Dots, hyphens, and spaces should be avoided.
Now we must create the app structure. Run:
flutter create .
This will scaffold out a new Flutter app with support for each of the platforms that are enabled. By default the enabled platforms are Android, iOS, and Web. If you enabled the desktop platforms above then it will also scaffold out those.
The main application code is stored inside the
lib/ folder, while each platform will have a respective folder to hold the native C and Java code. Normally you’d use Flutter plugins to enable native features and rely on coding your app in Dart. Flutter plugins can be discovered at pub.dev.
Test the app with:
flutter run -d linux
This will build and run the sample app.
It will also start a debugger server that you can connect to in your web browser; the URL will be in the output text when you run the app:
flutter run -d linux Running "flutter pub get" in flutter-sample... 392ms Launching lib/main.dart on Linux in debug mode... Building Linux application... Activating Dart DevTools... 4.5s Syncing files to device Linux... 89ms Flutter run key commands. r Hot reload. 🔥🔥🔥 R Hot restart. h Repeat this help message. d Detach (terminate "flutter run" but leave application running). c Clear the screen q Quit (terminate the application on the device). An Observatory debugger and profiler on Linux is available at: http://127.0.0.1:38399/PRAhGqkGwN0=/ Flutter DevTools, a Flutter debugger and profiler, on Linux is available at: http://127.0.0.1:9100?uri=http%3A%2F%2F127.0.0.1%3A38399%2FPRAhGqkGwN0%3D%2F
The debugging web page looks like this:
In this post, I showed how to install and configure Flutter and the Android toolchain, without hitting the issues that I encountered myself. I also showed creating and debugging a sample Flutter app, and enabling the toolchain for Linux, macOS, and Windows desktop apps.
Now we, you and I, just need to learn Dart and the Flutter APIs and create something amazing! Good luck…
Thanks again to Dan for authoring this post and permitting us to reproduce it here. Follow Dan’s writing over at diddledan.com.
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