Flutter Provider package, Consumer does not update UI, on removing item from list-CodePudding

As seen in the picture, i pressed the blue button 3 times, which added 3 card widgets in myList. Also in terminal it shows 3 items are added in myList. But when i longPress on 3rd Card to it, it infact removes from myList but does not update the UI.

Also, if i try removing 3rd item, again:

======== Exception caught by gesture ===============================================================
The following RangeError was thrown while handling a gesture:
RangeError (index): Invalid value: Not in inclusive range 0..1: 2

My full code is: (controller.dart)

    import 'package:flutter/cupertino.dart';

class MyController extends ChangeNotifier{
  var myList = [];

  void addItemsInList(){
    myList.add('item#${myList.length}    ');

    //todo: 1* forgot
    notifyListeners();
  }

  void removeItems(index){
    myList.removeAt(index) ;
  }
}

full code of view.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:provider_4/controller/controller_file.dart';

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return   MaterialApp(
        home: Consumer<MyController>(
          builder: (context, snapshot, child) {
            return Scaffold(
              floatingActionButton: FloatingActionButton(
                onPressed: (){
                  Provider . of <MyController> (context, listen: false) . addItemsInList();
                  print('myList.length gives: ${snapshot.myList.length}');
                  print(snapshot.myList);
                },
                child: Icon(Icons.add),
              ),
              body:   ListView.builder(
                itemCount: snapshot.myList.length , // replace with something like  myList.length
                itemBuilder: (context, index) =>   Card(
                  child: ListTile(
                    onLongPress: () {
                      Provider . of <MyController> (context, listen: false).removeItems(index);
                      // snapshot.myList.removeAt(index);
                      print(snapshot.myList);
                    },
                    title:   Text(
                      'Title', // replace with something like myList[index].title
                      style: TextStyle(
                        fontSize: 20,
                        color: Colors.black87,
                        fontWeight: FontWeight.bold,
                      ),
                    ),

                    subtitle:   Text(
                      'Details of title above', // replace with something like myList[index].details
                      style: TextStyle(
                        fontSize: 20,
                        color: Colors.deepPurple,
                        fontWeight: FontWeight.bold,

                      ),
                    ),
                    trailing: Icon(Icons.check_circle, color: Colors.green,),
                  ),
                ),
              ),
            );
          }
        ),
    );
  }
}

CodePudding user response：

You are getting RangeError because you are already deleting but the UI is not notified.

Add "notifyListeners();" at the end of the removeItems functions.

CodePudding user response：

try to add ValueKey to your ListTile

itemBuilder: (context, index) =>   Card(
   child: ListTile(
      key: UniqueKey(),
      onLongPress: () {
      .....