如何在Yocto构建的Allwinner A20 Cubieboard2登录时启动虚拟键盘

Great question! Since you’ve got core-image-sato up and running with LXDm on your Cubieboard 2, getting that virtual keyboard to auto-launch at the graphical login screen is straightforward. Let’s break this down step by step:

1. First, confirm your virtual keyboard is installed #

Core-image-sato usually includes matchbox-keyboard (a lightweight, perfect fit for embedded touch setups), but if it’s missing, add it to your Yocto build by editing conf/local.conf:

IMAGE_INSTALL:append = " matchbox-keyboard"

Rebuild your image, or use devtool to install it directly on your running system if you’re testing quickly.

2. Configure LXDm to launch the keyboard at login #

LXDm’s greeter (the login screen interface) has a few ways to auto-start applications. Pick whichever fits your workflow:

Method 1: Edit LXDm’s main config

Open /etc/lxdm/lxdm.conf and find the [base] section. Add this line to trigger the keyboard when the greeter loads:

greeter-setup-script=/usr/bin/matchbox-keyboard &

The & ensures the keyboard runs in the background so the login screen doesn’t hang. If you need to tweak the keyboard’s position or size (to fit your touchscreen), add parameters like -x 0 -y 400 -s 60 to set X/Y coordinates and key size.

Method 2: Add an autostart desktop file

Create a .desktop file in LXDm’s global autostart directory. Make /usr/share/lxdm/autostart/matchbox-keyboard.desktop with this content:

[Desktop Entry]
Name=Virtual Touch Keyboard
Comment=Launches matchbox keyboard for touch input
Exec=matchbox-keyboard
Type=Application
X-LXDM-Autostart=true

LXDm will automatically pick this up and launch the keyboard when the login screen loads.

Method 3: Use a custom script (for conditional logic)

If you want to only start the keyboard if a touchscreen is detected (smart for flexible setups), write a quick shell script. Save this as /usr/local/bin/start-touch-keyboard.sh:

#!/bin/sh
# Check for a touch input device
if ls /dev/input/event* | grep -qi touch; then
    matchbox-keyboard -x 0 -y 400 &  # Adjust position to your screen
fi

Make it executable:

chmod +x /usr/local/bin/start-touch-keyboard.sh

Then update /etc/lxdm/lxdm.conf to use this script instead:

greeter-setup-script=/usr/local/bin/start-touch-keyboard.sh

3. Test it out #

Restart LXDm to apply changes without a full reboot:

systemctl restart lxdm

Or just reboot your Cubieboard. You should see the virtual keyboard pop up automatically when the login screen appears.

Quick note on file locations #

• LXDm’s main config: /etc/lxdm/lxdm.conf
• Global autostart desktop files: /usr/share/lxdm/autostart/ or /etc/lxdm/autostart/
• Custom scripts: /usr/local/bin/ is the standard spot for user-added binaries

内容的提问来源于stack exchange，提问作者Joe Joe Ngigí