Flutter Reorderable ListView

file.dart

import 'package:flutter/material.dart';

class QuestionsPage extends StatefulWidget {
  
  @override
  _QuestionsPageState createState() => _QuestionsPageState();
}

class _QuestionsPageState extends State<QuestionsPage> {
  // List of items
  List<String> data = [ "a", "b", "c" ];

  @override
  Widget build(BuildContext context) {
    return Container(
      child: new ReorderableListView(
          children: data.map((i) => new ListTile(
            key: new ObjectKey(i),
            title: new Text(i),
            subtitle: new Text(i),
          )).toList(),
          onReorder: (int oldIndex, int newIndex) {
            // Check if the new index exceeds the length of the list
            // If yes, decrement the new index by one
            // This prevents list index out of range exception
            if (newIndex > oldIndex) {
              newIndex --;
            }
            
            // Finally, remove the item in the oldIndex and repopulate it in newIndex
            setState(() {
              String item = data.removeAt(oldIndex);
              data.insert(newIndex, item);
            });
          }
      ),
    );
  }
}