Launching on Simulator (ERROR)

hussam · July 2, 2026, 8:34am

Hello, MicroEJ team.

I created a new project Front Panel Mock and when testing the com.microej.demo.widget application on the Demo widget (SIM), I encountered this error:

=============== [ Initialization Stage ] ===============
=============== [ Converting fonts ] ===============
=============== [ Converting images ] ===============
=============== [ Launching on Simulator ] ===============
1 : ERROR :
[M17] - Error: [class java.lang.NoClassDefFoundError: ej/microui/display/LLUIPainter$MicroUIGraphicsContext].
(line 17 of stm32f746g_freertos-fp.fp)
<ej.fp.widget.Display x=“243” y=“143” width=“480” height=“272”/>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Thank you very much.

alexis.pineau · July 2, 2026, 3:02pm

Hello @hussam,

I’m assuming your project is a MICROEJ SDK5 project, please tell me if that’s not the case. The ej/microui/display/LLUIPainter$MicroUIGraphicsContext class that is not found comes from the UI Pack frontpanel library. It should be added as a dependency in your frontpanel’s module.ivy file. Here is an example of how it’s done in the STM32F7508-DK VEE Port:

github.com/MicroEJ/VEEPort-STMicroelectronics-STM32F7508-DK

stm32f7508_freertos-fp/module.ivy

master


      
          <ivy-module version="2.0" xmlns:ea="http://www.easyant.org" xmlns:ej="https://developer.microej.com" ej:version="2.0.0">

              <info organisation="com.mycompany" module="stm32f7508_freertos-fp" status="integration" revision="1.0.1"/>

          

          	<configurations defaultconfmapping="default->default;provided->provided">

          		<conf name="default" visibility="public" description="Runtime dependencies to other artifacts"/>

          		<conf name="provided" visibility="public" description="Compile-time dependencies to APIs provided by the platform"/>

          	</configurations>

          

              <dependencies>

                  <dependency org="ej.tool.frontpanel" name="widget" rev="2.0.0"/>

                  <dependency org="com.microej.pack.ui" name="ui-pack" rev="13.7.2">

          	       <artifact name="frontpanel" type="jar"/>

          		</dependency>

              </dependencies>

          </ivy-module>

Regards,
Alexis

hussam · July 3, 2026, 8:36am

Yes, I am using the MICROEJ SDK5 software development kit. I added ej/microui/display/LLUIPainter$MicroUIGraphicsContext as a dependency in the module.ivy file, but the error persists.

hussam · July 3, 2026, 9:29am

Okay, I’ve solved the problem. I found that the version of <dependency org="ej.library.ui" name="widget" rev="4.2.0" is different from <dependency org="ej.tool.frontpanel" name="widget" rev="2.0.0"/>, and I updated it to <dependency org="ej.tool.frontpanel" name="widget" rev="4.0.0"/>.

Thank you for your time.

alexis.pineau · July 3, 2026, 2:10pm

Hello @hussam,

Yes, ej.library.ui:widget is the library for the MICROEJ runtime, while ej.tool.frontpanel.widget is the library for the frontpanel.

What your frontpanel was missing was the UI Pack frontpanel artifact as I said in my previous message, this artifact is retrieved transitively by the frontpanel widget library, that’s why it’s working now.

Have a good day,
Alexis