我是新人。我已经了解了Libgdx。我的项目之前正常运行。但今天，我有两个错误。
java.lang.NullPointerException: Attempt to invoke interface method 'void java.lang.Runnable.run()' on a null object reference
at com.badlogic.gdx.scenes.scene2d.actions.RunnableAction.run(RunnableAction.java:42)
at com.badlogic.gdx.scenes.scene2d.actions.RunnableAction.act(RunnableAction.java:32)
at com.badlogic.gdx.scenes.scene2d.actions.SequenceAction.act(SequenceAction.java:65)
at com.badlogic.gdx.scenes.scene2d.Actor.act(Actor.java:95)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:46)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:49)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:49)
at com.sgroup.jqkpro.base.ABSUser.act(ABSUser.java:1116)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:49)
at com.badlogic.gdx.scenes.scene2d.Stage.act(Stage.java:223)
at com.sgroup.jqkpro.screens.MainScreen.update(MainScreen.java:228)
at com.sgroup.jqkpro.screens.DefaultScreen.render(DefaultScreen.java:55)
at com.badlogic.gdx.Game.render(Game.java:46)
at com.badlogic.gdx.backends.android.AndroidGraphics.onDrawFrame(AndroidGraphics.java:422)
at android.opengl.GLSurfaceViewGLThread.guardedRun(GLSurfaceView.java:1522)
at android.opengl.GLSurfaceViewGLThread.run(GLSurfaceView.java:1239)
java.lang.NullPointerException: Attempt to invoke virtual method 'float com.badlogic.gdx.scenes.scene2d.Actor.getX(int)' on a null object reference
at com.badlogic.gdx.scenes.scene2d.actions.MoveToAction.begin(MoveToAction.java:29)
at com.badlogic.gdx.scenes.scene2d.actions.TemporalAction.act(TemporalAction.java:48)
at com.badlogic.gdx.scenes.scene2d.actions.SequenceAction.act(SequenceAction.java:65)
at com.badlogic.gdx.scenes.scene2d.Actor.act(Actor.java:95)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:46)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:49)
at com.badlogic.gdx.scenes.scene2d.Group.act(Group.java:49)
at com.badlogic.gdx.scenes.scene2d.Stage.act(Stage.java:223)
at com.sgroup.jqkpro.screens.MainScreen.update(MainScreen.java:229)
at com.sgroup.jqkpro.screens.DefaultScreen.render(DefaultScreen.java:55)
at com.badlogic.gdx.Game.render(Game.java:46)
at com.badlogic.gdx.backends.android.AndroidGraphics.onDrawFrame(AndroidGraphics.java:422)
at android.opengl.GLSurfaceViewGLThread.guardedRun(GLSurfaceView.java:1522)
at android.opengl.GLSurfaceViewGLThread.run(GLSurfaceView.java:1239)
我不知道为什么。请告诉我如何修复 Tks all。