Updating existing custom message types with rosgenmsg

Technical Source
3 min readApr 2, 2021


I am trying to use the Leap Motion ROS package through matlab. The ROS toolbox came preloaded with the following message types related to Leap Motion


However, these message type relate to version 0.0.4 of the leap motion ros package. The ROS group has since come out with version 0.0.9 that contains the same message names but completely different msg files.

I have tried, but keep failing, when I try to create the custom message package for these message types. Every time I create the package, the created message type refers back to the 0.0.4 format. I have tried removing the leap_motion folder from the matlab toolbox/robotics folder and I have tried also removing the same folder and jar file from the addons folders, but the created package still refers back to the 0.0.4 format. When I look at the .m files created in matlab_gen for this package, the message information does not reflect the .msg files for the newer package.

I also created a package leap_motion_test that contained the exact same msg files and the same package.xml (with the name changed) and ran this through rosgenmsg. This creates the correct message package that relates to 0.0.9. This leads me to believe that there is something in the matlab code that is seeing the existing message types and then alters the way rosgenmsg works.

Can anyone help me with this? It is extremely frustrating. I thought I was onto the right solution by removing the existing packages from matlab. When I run

rosmsg list

the messages types for leap_motion no longer appeared but when I ran the rosgenmsg, the results were incorrect. Is there another place where matlab stores information about its existing headers? Is there someway that I should format the new package so that matlab accepts that it is ok to update it.


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Sorry that you are having trouble updating the message definition for the leap_motion package. You can replace the builtin definition as follows:

  • Download the leap_motion folder containing the new message definitions. I think you already have this folder. In the remainder of the instructions, I will assume that this leap_motion folder is placed in c:\customrosmsg.
  • Run rosgenmsg on the folder containing the custom message definitions:
rosgenmsg c:\customrosmsg
  • Follow the instructions to edit the javaclasspath.txt file. In addition to the JAR file path, you also need to tell MATLAB to use this JAR file instead of the builtin one. Add the “before” token in front of the JAR file file path:
  • Restart MATLAB
  • Delete the previously generated MATLAB files and run rosgenmsg again. Now, it should pick up the new definitions:





Technical Source

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