This appeared as I was trying to use a mouseEvent to move an object.
I placed the variables for mouseX and mouseY in the public class. I did the same for direction X and Y but there was no error message for those.
See Question&Answers more detail:
os 与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…