Flutter logic issue

Question

I'm building this small game , it's similar to Qix game .

I already built the first screens now i need to implement the functionality , the car should be moving using the buttons , and while moving it should draw like a container behind it until it feel all the stadium .

this is where I'm making the car moves :

class _GameScreenState extends State<GameScreen> {
  double xPosition = Random().nextInt(230).toDouble();
  double yPposition = Random().nextInt(200).toDouble();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Container(
          height: MediaQuery.of(context).size.height,
          width: MediaQuery.of(context).size.width,
          decoration: BoxDecoration(
            image: DecorationImage(
              image: AssetImage("assets/images/bg.png"),
              fit: BoxFit.cover,
            ),
          ),
          child: Column(
            children: [
              // Game play
              Expanded(
                flex: 6,
                child: Stack(
                  children: [
                    Container(
                      height: MediaQuery.of(context).size.height,
                      width: MediaQuery.of(context).size.width,
                      color: Colors.transparent,
                    ),
                    Positioned(
                      bottom: yPposition,
                      left: xPosition,
                      child: Image.asset("assets/images/car.png"),
                    )
                  ],
                ),
              ),
              // Player inputes
              Expanded(
                child: Container(
                  child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: Row(
                      mainAxisAlignment: MainAxisAlignment.spaceBetween,
                      children: [
                        Row(
                          children: [
                            RoundIconButton(
                              onPress: () {
                                setState(() {
                                  yPposition--;
                                });
                              },
                              icon: Icons.arrow_downward,
                            ),
                            RoundIconButton(
                              onPress: () {
                                setState(() {
                                  yPposition++;
                                });
                              },
                              icon: Icons.arrow_upward,
                            ),
                          ],
                        ),
                        Row(
                          children: [
                            RoundIconButton(
                              onPress: () {
                                setState(() {
                                  xPosition--;
                                });
                              },
                              icon: Icons.arrow_back,
                            ),
                            RoundIconButton(
                              onPress: () {
                                setState(() {
                                  xPosition = xPosition + 10;
                                });
                              },
                              icon: Icons.arrow_forward,
                            ),
                          ],
                        ),
                      ],
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

I also need the car keep moving when I press the button , in my case it moves only one time