Tween engine issue

Newbie & Debugging Questions
#1

I use Libgdx and Tween engine. I get a weird problem when registering accessor like this.

EDIT: It seems that my Eclipse cant even find SpriteAccessor();. I installed Libgdx and Tween with the libGdx GUI installer. any advice how to fix this?

this class implements Screen

@Override
	public void show() {
		splashTexture = new Texture(Gdx.files.internal("img/splash.png"));
		splash = new Sprite(splashTexture);
		splash.setSize(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
		
		batch = new SpriteBatch();
		tweenManager = new TweenManager();
		Tween.registerAccessor(Sprite.class, new SpriteAccessor()); //Here the SpriteAccessor is underlined
		
		splashBgm = Gdx.audio.newMusic(Gdx.files.internal("sounds/bgm.mp3"));
		splashBgm.setVolume(.2f);
		splashBgm.setLooping(true);
		splashBgm.play();
	}

And here is my ScreenAccessor class that implements TweenAccessor

@Override
	public int getValues(Sprite target, int tweenType, float[] returnValues) {
		switch(tweenType){
		case ALPHA:
			returnValues[0] = target.getColor().a;
			return 1;
		default:
			assert false;
			return -1;
		}	
	}

	@Override
	public void setValues(Sprite target, int tweenType, float[] newValues) {
		switch(tweenType){
		case ALPHA:
			target.setColor(target.getColor().r, target.getColor().g, target.getColor().b, newValues[0]);
			break;
		default:
			assert false;
		}
	}

Thank you.