LateInitializationError: Field 'productItem' has not been initialized

Question

I am building a flutter app and I am getting a LateInitialization error on the productItem field. I made an instance of the ProductItem class so that I could access and pass the instance variables to my methods in the ProductItemState class. I also tried making the field nullable but I then ended up getting a "unexpect null value" error. I'm not sure which other way I can access those instance variables in my ProductItemState class. Please can anyone kindly assist.

class ProductItem extends StatefulWidget {
  String id;
  String bottleName;
  String imgUrl;
  double price;
  Bottle bottle;
  ProductItem(
      {Key? key,
      required this.id,
      required this.bottleName,
      required this.imgUrl,
      required this.price,
      required this.bottle})
      : super(key: key);

  @override
  State<ProductItem> createState() => _ProductItemState();
}

class _ProductItemState extends State<ProductItem>
    with AutomaticKeepAliveClientMixin {
    late ProductItem productItem;
  @override
  bool get wantKeepAlive => true;
  @override
  Widget build(BuildContext context) {
    super.build(context);
    var cart = Provider.of<ShoppingCartProvider>(context);
    var favoriteProvider = Provider.of<FavoriteProvider>(context);
    return Card(
      shadowColor: Colors.grey,
      surfaceTintColor: Colors.amber,
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
      child: Stack(
        children: [
          Positioned(
            right: 0,
            child: InkWell(
              onTap: () {
                favoriteProvider.toggleFavorites(productItem.bottle);
                if (favoriteProvider.isExist(productItem.bottle)) {
                  ScaffoldMessenger.of(context).hideCurrentSnackBar();
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(
                      content: Text(
                        "Product Added to Favorite!",
                        style: TextStyle(fontSize: 16),
                      ),
                      backgroundColor: Colors.green,
                      duration: Duration(seconds: 1),
                    ),
                  );
                } else {
                  ScaffoldMessenger.of(context).hideCurrentSnackBar();
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(
                      content: Text(
                        "Product Removed from Favorite!",
                        style: TextStyle(fontSize: 16),
                      ),
                      backgroundColor: Colors.red,
                      duration: Duration(seconds: 1),
                    ),
                  );
                }
              },
              child: favoriteProvider.isExist(productItem.bottle)
                  ? Icon(
                      Icons.favorite,
                      color: Colors.redAccent,
                    )
                  : Icon(Icons.favorite_border),
            ),
          ),
          Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Center(
                child: Image.asset(
                  productItem.imgUrl,
                  height: 200.0,
                ),
              ),
              Center(
                  child: Text(productItem.bottleName,
                      style: const TextStyle(
                          fontSize: 20.0, fontWeight: FontWeight.bold))),
              Center(
                child: Text('R${productItem.price}'),
              )
            ],
          ),
          Positioned(
              bottom: 0,
              right: 10,
              child: IconButton(
                icon: const Icon(Icons.add_circle),
                iconSize: 40.0,
                onPressed: () {
                  cart.addToCart(productItem.id, productItem.bottleName,
                      productItem.price, productItem.imgUrl);
                },
              ))
        ],
      ),
    );
  }
}

Answer 1

You need to start productItem variable. When you use late, you guarantee that you will start right after this variable.

Use

Product product = Product(id, name);

Instead of

late Product product;

or

late Product product;
product = Product(id, name);

Edit:

I'm adding below the code I put in the comment link of this answer and which @Anesu said worked.

class ProductItem {
  String id;
  String bottleName;
  String imgUrl;
  String price;
  Bottle bottle;

  ProductItem({required this.id, required this.bottleName, required this.imgUrl, required this.price});
}

class ProductItemPage extends StatefulWidget {
  ProductItem item;
  
  ProductItemPage(
      {Key? key,
      required this.item})
      : super(key: key);

  @override
  State<ProductItemPage> createState() => _ProductItemPageState();
}

class _ProductItemPageState extends State<ProductItemPage>
    with AutomaticKeepAliveClientMixin {
  
   late ProductItem productItem;
  
  @override
  void initState() {
    super.initState();
    productItem = widget.item;
  }
  
  @override
  bool get wantKeepAlive => true;
  @override
  Widget build(BuildContext context) {
    super.build(context);
    var cart = Provider.of<ShoppingCartProvider>(context);
    var favoriteProvider = Provider.of<FavoriteProvider>(context);
    return Card(
      shadowColor: Colors.grey,
      surfaceTintColor: Colors.amber,
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
      child: Stack(
        children: [
          Positioned(
            right: 0,
            child: InkWell(
              onTap: () {
                favoriteProvider.toggleFavorites(productItem.bottle);
                if (favoriteProvider.isExist(productItem.bottle)) {
                  ScaffoldMessenger.of(context).hideCurrentSnackBar();
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(
                      content: Text(
                        "Product Added to Favorite!",
                        style: TextStyle(fontSize: 16),
                      ),
                      backgroundColor: Colors.green,
                      duration: Duration(seconds: 1),
                    ),
                  );
                } else {
                  ScaffoldMessenger.of(context).hideCurrentSnackBar();
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(
                      content: Text(
                        "Product Removed from Favorite!",
                        style: TextStyle(fontSize: 16),
                      ),
                      backgroundColor: Colors.red,
                      duration: Duration(seconds: 1),
                    ),
                  );
                }
              },
              child: favoriteProvider.isExist(productItem.bottle)
                  ? Icon(
                      Icons.favorite,
                      color: Colors.redAccent,
                    )
                  : Icon(Icons.favorite_border),
            ),
          ),
          Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Center(
                child: Image.asset(
                  productItem.imgUrl,
                  height: 200.0,
                ),
              ),
              Center(
                  child: Text(productItem.bottle,
                      style: const TextStyle(
                          fontSize: 20.0, fontWeight: FontWeight.bold))),
              Center(
                child: Text('R${productItem.price}'),
              )
            ],
          ),
          Positioned(
              bottom: 0,
              right: 10,
              child: IconButton(
                icon: const Icon(Icons.add_circle),
                iconSize: 40.0,
                onPressed: () {
                  cart.addToCart(productItem.id, productItem.bottleName,
                      productItem.price, productItem.imgUrl);
                },
              ))
        ],
      ),
    );
  }
}

Answer 2

late means you are telling Flutter that i will make sure that this field gets initialized, don't do null checks on this variable. But you are using late and not initializing productItem, which is resulting in runtime error