how to fix it?
You'll need to give some more details on what you're doing exactly to cause this error. Is this from a built game? Is this when you try to compile/run your project? Did you use setup.gdx?
is a runtime exception
i download gdx from github
For creating a project, i strongly suggest using the setup jar file: https://libgdx.badlogicgames.com/nightlies/dist/gdx-setup.jar, and then have a look in the wiki: for getting it going in your IDE of choice.
Please see https://github.com/libgdx/libgdx/wiki/Issue-Tracker before creating issues on the tracker.
If you believe you have found an issue, please do not delete the issue template, and make sure to fill it in correctly.