Setting up FImage for Application Development

This guide will explain how to bring your existing Flutter application to Fuchsia using the Flutter SDK and FImage.

Prerequisites

You'll need a few things before working with Flutter apps on Fuchsia:

A working installation of the latest version of the FImage tool (opens in a new tab).
The Flutter SDK (opens in a new tab).
The ssh-keygen tool.

Configuring Flutter for Fuchsia

Begin by upgrading Flutter to the master channel.

flutter channel master

Then, Enable Fuchsia development, and upgrade the Flutter tool. It should download the Fuchsia SDK. If flutter devices does not list the fuchsia_fimage device, run this step again.

flutter config --enable-fuchsia && flutter upgrade

Provisioning SSH Keys to FImage

To start, generate a new set of SSH keys for the emulator:

ssh-keygen

For the sake of organization, call the key fimage_key. Don't set a password for the keypair. You should see an output similar to below.

Generating public/private rsa key pair.
Enter file in which to save the key (/home/nmcain/.ssh/id_rsa): fimage_key
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in fimage_key
Your public key has been saved in fimage_key.pub
The key fingerprint is:
SHA256:yJz40GaEI+pyfBaTgC9n2HGlGDBEBVYeLVV3PyCd99A nmcain@OptiPlex-790
The key's randomart image is:
+---[RSA 3072]----+
|=*=+o.o. o.o. .  |
|.o.+.=  . oooo E |
|. =.* .     .oo  |
| = = O o      .. |
|+ = * O S        |
|.=   B           |
|..o o .          |
|.. o             |
|                 |
+----[SHA256]-----+

Now that the key has been generated, send the public key to FImage. Make sure the emulator is not started, and use the ZBI tool to inject the key.

./tools/zbi -o init/fuchsia-ssh.zbi init/fuchsia.zbi --replace --entry data/ssh/authorized_keys=/home/$USER/.ssh/fimage_key.pub

Starting and Checking FImage

Now that SSH and the SDK are configured, you can start FImage by running:

./network-config
./fimage-gui 4096

In a new terminal, check that the emulator is running and recognized by Flutter, using the flutter devices command as shown below:

nmcain@OptiPlex-790 ~/fimage$ flutter devices
3 connected devices:

fuchsia_fimage (null) • fe80::98bb:89e1:a5cf:daab%brqemu • fuchsia-x64    • Fuchsia 2021-05-26T01:49:18+00:00
Linux (desktop)       • linux                            • linux-x64      • Ubuntu 20.04.2 LTS 5.8.0-53-generic
Chrome (web)          • chrome                           • web-javascript • Google Chrome 91.0.4472.77

Your device is now ready to run Flutter apps!

Preparing and Running a Flutter App

The instructions for this step can be found at Preparing and Running a Flutter App.

Developers Run app on FImage