Flutter ListView doesn't update on setState

Question

My flutter ListView doesn't update when my setState runs in my State class.

Yes, My main class is a stateful widget, incase anyone was wondering

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => new _MyAppState();
}

My setState function

setState(() {
        if (price == "null") {
          items.add("Item ${counter + 1}: error");
          print("null");
        } else {
          items.add("Item ${counter + 1}: $price");
          print("$price");
          totalPrice += price;
        }
        counter++;
      });
    });

Before I placed my ListView within a Container -> Column -> Expanded it was working fine. But after I added it, it stopped updating when my setState ran

body: new Container(
         child: Column(
           children: <Widget>[
             Expanded(
               child: ListView.builder(
                 itemCount: items.length,
                 itemBuilder: (context, index) {
                   final item = items[index];

                   return Dismissible(
                     key: Key(item),
                     onDismissed: (direction) {
                       setState(() {
                         items.removeAt(index);
                         counter--;
                       });
                       Scaffold.of(context).showSnackBar(
                           SnackBar(content: Text("$item deleted")));
                     },
                     background: Container(color: Colors.red),
                     child: ListTile(title: Text('$item')),
                   );
                 },
               ),
             ),

Could someone who is more knowledgeable in flutter educate me on what's going on here. I don't think adding the ListView into a container should make that much of a difference to how it works right?

ExPlOiD ExPlOiD · Accepted Answer · 2020-07-26T22:06:40

Doing computations in setstate somehow caused this problem. Instead I did the computations in build since and I used setstate to only add to the list. It’ll then trigger the build and the rest of the things happen there. This solved my problem

Flutter ListView doesn't update on setState

1 Answers