Unable to access Class / State method using GlobalKey

Question

Im working on an app where users can add items to a cart and i need to be able to clear the cart if the user so wishes.

The representation uses a GridLayout where I represent each item as a stateful GridItemCard (so as to maintain a count of the items added to the cart, which is a Singleton class with a List that contains the items added.

I am able to add and remove items, and maintain state in general but when I try to clear the cart, I need to update each GridItemCard to reset it to 0. (I maintain a manual counter inside for each item's count).

I now need to access the individual instances of the GridItemCards, and research indicates that accessing the Keys of each is better than adding them to a list in the main class and trying to access them.

Research:

I used the following SO answer to build the logic :

Based on this, list clearing should work using Keys to access but for some reason accessing the key from a list doesn't work. What is it that I'm missing?


class GridItemCard extends StatefulWidget {
  final Item item;
  final Function addItem;
  final Function removeItem;
  final Function clearItem;
  //final int? itemCount;
  final int? regular;
  final int? regularStarch;
  final int? stainRemoval;
  final int? stainRemovalStarch;

  GridItemCard({ required this.item, required this.addItem, required this.removeItem, required this.clearItem, Key? key, this.regular, this.regularStarch, this.stainRemoval, this.stainRemovalStarch}) : super(key: key);

  @override
  GridItemCardState createState() => GridItemCardState();
}

class GridItemCardState extends State<GridItemCard> with AutomaticKeepAliveClientMixin {
  int count = 0;
  int regular = 0;
  int regularStarch = 0;
  int stainRemoval = 0;
  int stainRemovalStarch = 0;

  //int regularLive = widget.items[]

  @override
  void initState() {
    super.initState();
    regular = widget.regular ?? 0;
    regularStarch = widget.regularStarch ?? 0;
    stainRemoval = widget.stainRemoval ?? 0;
    stainRemovalStarch = widget.stainRemovalStarch ?? 0;
    count = regular + regularStarch + stainRemoval + stainRemovalStarch;
  }

  void clearCount(){
    regular =0;
    regularStarch = 0;
    stainRemoval =0;
    stainRemovalStarch = 0;
    count = 0;
  }

To add the items and Keys, I do the following :

  Widget getGridCard(Color color, Map<String, dynamic> item, String category) {
    Item thisItem = Item.fromJson(item);
    String itemId = thisItem.id ?? "";
    print(category);
    var ret = cart.itemCounter(itemId, category);

    int regular = ret.$1;
    int regularStarch = ret.$2;
    int stainRemoval = ret.$3;
    int stainRemovalStarch = ret.$4;
    int count = regular + regularStarch + stainRemoval + stainRemovalStarch;

    setState(() {});
    final gcKey = GlobalKey<GridItemCardState>();
    GridItemCard gc = GridItemCard(
      item: thisItem,
      addItem: addItem,
      removeItem: removeItem,
      key: gcKey,
      regular: regular,
      regularStarch: regularStarch,
      stainRemoval: stainRemoval,
      stainRemovalStarch: stainRemovalStarch,
    );
    allYourGCsAreBelongToUs.add(gcKey);
    return gc;
  }

However when I try using the Key to access the element and the embedded method, I get a blank:

void clearCart(){

    cart.clear(); // clear the data in the Cart SingleTon
   
    // now loop through the GC list and clear each cart's display
    for(GlobalKey gc in allYourGCsAreBelongToUs){
      gc.currentState.clearCount();
    }
   
    setState(() {

    });
  }

The error I get is :

lib/shopping_cart.dart:870:23: Error: The method 'clearCount' isn't defined for the class 'State?'.

'State' is from 'package:flutter/src/widgets/framework.dart' ('/opt/flutter/packages/flutter/lib/src/widgets/framework.dart').

'StatefulWidget' is from 'package:flutter/src/widgets/framework.dart' ('/opt/flutter/packages/flutter/lib/src/widgets/framework.dart'). Try correcting the name to the name of an existing method, or defining a method named 'clearCount'. gc.currentState.clearCount();

Unable to access Class / State method using GlobalKey

0 Answers0