In libgdx, how do I get input from the back button?

I solved the problem like this:

public class MyApplication implements ApplicationListener, InputProcessor {
   // !! Remember to override all other required methods !!
   ...

   @Override
   public void create() {
        Gdx.input.setInputProcessor(this);
        Gdx.input.setCatchBackKey(true);
        // rest of your stuff...
   }

   ...

   @Override
   public boolean keyDown(int keycode) {
        if(keycode == Keys.BACK){
           // Do your optional back button handling (show pause menu?)
        }
        return false;
   }

   ...
}

Not copypasta stuff but hopefully this helps you out. 🙂