| Key | Value |
|---|---|
| Summary | Learn how to build and deploy a Flutter application on Ubuntu Core by leveraging Ubuntu Frame |
| Categories | iot |
| Difficulty | 3 |
| Author | Bugra Aydogar bugra.aydogar@canonical.com |
Overview
Duration: 3:00
This document has been supersede:
6 Likes
after following the above steps, I got this.
asimfarooq5@ubuntu:~$ flutterdemo
error: error running snapctl: snap "flutterdemo" has no plug or slot named "pulseaudio"
WARNING: pulseaudio interface not connected! Please run: /snap/flutterdemo/current/bin/setup.sh
Setting up watches.
Watches established.
asimfarooq5@ubuntu:~$ snap logs flutterdemo
2022-01-11T14:39:18Z flutterdemo.daemon[1620]: WARNING: pulseaudio interface not connected! Please run: /snap/flutterdemo/current/bin/setup.sh
2022-01-11T14:39:18Z -[1620]: g_dbus_proxy_new_sync: assertion 'G_IS_DBUS_CONNECTION (connection)' failed
2022-01-11T14:39:18Z flutterdemo.daemon[1620]: Couldn't open libGLESv1_CM.so.1: libGLESv1_CM.so.1: cannot open shared object file: No such file or directory
2022-01-11T14:39:18Z systemd[1]: snap.flutterdemo.daemon.service: Main process exited, code=exited, status=1/FAILURE
2022-01-11T14:39:18Z systemd[1]: snap.flutterdemo.daemon.service: Failed with result 'exit-code'.
2022-01-11T14:39:18Z systemd[1]: snap.flutterdemo.daemon.service: Scheduled restart job, restart counter is at 6.
2022-01-11T14:39:18Z systemd[1]: Stopped Service for snap application flutterdemo.daemon.
2022-01-11T14:39:18Z systemd[1]: snap.flutterdemo.daemon.service: Start request repeated too quickly.
2022-01-11T14:39:18Z systemd[1]: snap.flutterdemo.daemon.service: Failed with result 'exit-code'.
2022-01-11T14:39:18Z systemd[1]: Failed to start Service for snap application flutterdemo.daemon.
That isn’t in the instructions and won’t work: There’s no Wayland server in your user session.
This is your problem: there’s an error in your snap packaging that prevents libGLESv1_CM.so.1 being found. Please recheck your snap recipe.
this is my “snapcraft.yaml”
name: flutterdemo
base: core18
version: '0.1'
summary: flutterdemo
description: flutterdemo
grade: devel
confinement: devmode
slots:
dbus-flutterdemo:
interface: dbus
bus: session
name: com.example.flutterdemo
apps:
daemon:
daemon: simple
restart-condition: always
command-chain:
- bin/run-daemon
- bin/wayland-launch
command: bin/flutterdemo
extensions: [flutter-master]
environment:
GDK_GL: gles
flutterdemo:
command-chain:
- bin/wayland-launch
command: flutterdemo
extensions: [flutter-master]
environment:
GDK_GL: gles
parts:
flutterdemo:
source: .
plugin: flutter
flutter-target: lib/main.dart
mir-kiosk-snap-launch:
plugin: dump
source: https://github.com/MirServer/mir-kiosk-snap-launch.git
override-build: $SNAPCRAFT_PART_BUILD/build-with-plugs.sh opengl wayland
stage-packages:
- inotify-tools
layout:
/usr/share/fonts:
bind: $SNAP/usr/share/fonts
/etc/fonts:
bind: $SNAP/etc/fonts
/usr/share/icons:
bind: $SNAP/usr/share/icons
I’m testing on nvidia, does this matters ?
At what point in the tutorial are you? “Running Your Flutter Application Snap on Ubuntu Core”?
What device (or VM) are you running on?
yeah, I’m trying on UbuntuCore in Qemu(VM).
after removing pulseaudio from snapcraft.yaml
asimfarooq5@ubuntu:~$ flutterdemo
Setting up watches.
Watches established.
asimfarooq5@ubuntu:~$ snap logs flutterdemo
2022-01-12T11:25:28Z flutterdemo.daemon[2498]: + exec /snap/flutterdemo/x2/bin/wayland-launch /snap/flutterdemo/x2/bin/flutterdemo
2022-01-12T11:25:28Z -[2498]: g_dbus_proxy_new_sync: assertion 'G_IS_DBUS_CONNECTION (connection)' failed
2022-01-12T11:25:28Z flutterdemo.daemon[2498]: Couldn't open libGLESv1_CM.so.1: libGLESv1_CM.so.1: cannot open shared object file: No such file or directory
2022-01-12T11:25:28Z systemd[1]: snap.flutterdemo.daemon.service: Main process exited, code=exited, status=1/FAILURE
2022-01-12T11:25:28Z systemd[1]: snap.flutterdemo.daemon.service: Failed with result 'exit-code'.
2022-01-12T11:25:28Z systemd[1]: snap.flutterdemo.daemon.service: Scheduled restart job, restart counter is at 5.
2022-01-12T11:25:28Z systemd[1]: Stopped Service for snap application flutterdemo.daemon.
2022-01-12T11:25:28Z systemd[1]: snap.flutterdemo.daemon.service: Start request repeated too quickly.
2022-01-12T11:25:28Z systemd[1]: snap.flutterdemo.daemon.service: Failed with result 'exit-code'.
2022-01-12T11:25:28Z systemd[1]: Failed to start Service for snap application flutterdemo.daemon.
This probably won’t work, but I’d like to verify that it doesn’t to eliminate possible causes, could you try running this:
$ echo "env -u GDK_GL \$SNAP/bin/flutterdemo" | sudo snap run --shell flutterdemo
1 Like
Cool. In that case, you simply need to remove the GDK_GL: gles lines from your snapcraft recipe and repackage. These lines are there because they are needed on some devices (e.g. RPi4). Unfortunately, it seems that they break things on QEMU.
We’ll need to do some more investigation into how to get this example working across all devices.
1 Like
yeah, It working fine, I’ll repackage this for arm64 and test on RPi3&4.
OK, the root cause is that the gnome-3-28-1804 snap is intended for desktop use and, since for amd64, there’s no need for GLES it doesn’t contain libgles1.
There’s another approach to building Flutter snaps for Core that does work across devices. The general approach is described here:
https://github.com/MirServer/iot-example-graphical-snap/wiki/Embedding-IOT-GUI-with-Ubuntu-Frame
With a Flutter specific branch here:
https://github.com/MirServer/iot-example-graphical-snap/tree/Flutter-demo
I have build the snap with same config removing the GDK_GL: gles lines and got this in snap logs:
Failed to start Flutter renderer: Unable to create a GL context
I’d expect to see that on RPi4.
In any case, I’ve just updated the snapcraft.yaml in the tutorial. That should work everywhere.
I tested with RPi3, let me test the updated config.
i’d do that type of detection at runtime instead of build time:
gles-on-arm:
plugin: nil
override-build: |
snapcraftctl build
mkdir -p $SNAPCRAFT_PART_INSTALL/bin/
echo 'case $(arch) in aarch64|armv7l) export GDK_GL=gles;; esac' > $SNAPCRAFT_PART_INSTALL/bin/gl-launch
echo 'exec "$@"' >> $SNAPCRAFT_PART_INSTALL/bin/gl-launch
chmod a+x $SNAPCRAFT_PART_INSTALL/bin/gl-launch
new snapcraft.yaml in the tutorial works fine for both amd64/arm64. 
1 Like
There are many equivalent ways to do this. 
Hi, I’m trying to run this example in a raspberry pi 4 using ubuntu core 20, but after install ubuntu-frame and the super-cool-app snap, I only get the grey wallpaper from ubuntu-frame but no signal of the flutter app.
I added this to the snapcraft.yaml file to make the snap compatible with armhf architercture:
architectures:
- build-on: amd64
run-on: armhf
Also, when I run super-cool-app on the command line, I get this messages:
error: error running snapctl: snap "super-cool-app" has no plug or slot named "pulseaudio"
WARNING: pulseaudio interface not connected! Please run: /snap/super-cool-app/current/bin/setup.sh
/snap/super-cool-app/x2/bin/wayland-launch: 22: /snap/super-cool-app/x2/bin/wayland-launch: inotifywait: Exec format error
Any help will be very appreciated.