Changing Image displayed on UI on button tap flutter

How can I refresh the page on button tap? I am displaying one default image which is initialized at the beggining with some url. My goal is when I press a button refresh that image. For that, I placed a button in other part of the code and I refresh the state changing the value of the variable (url) with the one I want to display:

The card where I want to refresh the image with the variable urlImgCard.

 Expanded(
                                            child: Container(
                                              decoration: BoxDecoration(
                                                borderRadius:
                                                    const BorderRadius.only(
                                                        topLeft:
                                                            Radius.circular(15),
                                                        topRight:
                                                            Radius.circular(
                                                                15)),
                                                image: DecorationImage(
                                                  image: NetworkImage(
                                                    urlImgCard,
                                                  ),
                                                  fit: BoxFit.cover,
                                                ),
                                              ),
                                            ),
                                          ),

This is how I initialize the variable with a default url:

child: FloatingActionButton(
                                        shape: RoundedRectangleBorder(
                                            borderRadius:
                                                BorderRadius.circular(10)),
                                        child: const Text('Show'),
                                        onPressed: () async {
                                          setState(() {
                                            showImgPushed = true;
                                            urlImgCard =
                                                AppConstants.BACK4APP_IMG_URL +
                                                    snapshot.data![currentIndex
                                                        as int]['DogImg'];
                                          });

beginning of the code, in initState:

  var urlImgCard;
  @override
  void initState() {
    super.initState();
    setState(() {
      urlImgCard = AppConstants.QUESTION_MARK_IMG;
    });