Update CheckboxListTile from a list variable. Flutter-CodePudding

I'm writing a taskList class that should allow me to check tasks as done. Everything works except for the Checkbox itself. I cannot get the screen to update the checkBox to actually check. onChanged part of each checkbox is where I should be able to update not only the screen but also the boolean isCompleted of each task with setState. Unfortunately, the only way I have been able to get onChanged to work, ie. check the box, is by declaring variables in the class itself and using those instead.

For this reason I believe that the issue has to do with me using a variable within an object. I think that flutter doesn't recognize that when userTaskList[index].isComplete is changed it will affect the screen so it doesn't bother rebuilding. I'm new to flutter so this could be totally wrong. ** I click on the checkbox, it changes variables, it does not update the screen with a check mark in the box.**

Here is the where the problem is in my TaskList Widget

import 'package:flutter/material.dart';
import '../models/task.dart';
import 'package:intl/intl.dart';

class TaskList extends StatefulWidget {
  const TaskList({super.key});
  @override
  State<TaskList> createState() => _TaskListState();
}

class _TaskListState extends State<TaskList> {
  @override
  Widget build(BuildContext context) {
    List<Task> userTaskList = [
      Task(name: "Spanish Hw", dueDate: DateTime.now(), priority: 1),
      Task(name: "Push Day", dueDate: DateTime.now(), priority: 3),
      Task(name: "English HL Essay", dueDate: DateTime.now(), priority: 2)
    ];

    return Container(
      height: 300,
      margin: const EdgeInsets.all(20),
      child: ListView.builder(
        itemCount: userTaskList.length,
        itemBuilder: ((context, index) {
          return Dismissible(
              key: ValueKey(userTaskList[index]),
              onDismissed: (direction) {
                userTaskList.removeAt(index);
              },
              direction: DismissDirection.startToEnd,
              background: Container(
                  padding: const EdgeInsets.all(10),
                  alignment: Alignment.centerLeft,
                  color: Colors.red,
                  child: const Icon(
                    Icons.delete,
                    color: Colors.white,
                  )),
              child: Card(
                elevation: 10,
                child: SizedBox(
                  height: 50,
                  **child: CheckboxListTile(
                    //subtitle: Text(taskList[index].description),
                    activeColor: Colors.green,
                    value: userTaskList[index].isComplete,
                    onChanged: (val) {
                      print('Checkbox clicked, new value: $val');
                      setState(() {
                        userTaskList[index].isComplete = val ?? false;
                      });
                    },**
                    title: Row(
                      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                      children: [
                        Text(
                          userTaskList[index].name,
                          textAlign: TextAlign.center,
                        ),
                        Text(
                          DateFormat('EEEE, MMM D')
                              .format(userTaskList[index].dueDate),
                          textAlign: TextAlign.right,
                        ),
                      ],
                    ),
                  ),
                ),
              ));
        }),
      ),
    );
  }
}

And Just incase it is important here is my Task class

import 'package:flutter/material.dart';

class Task {
  bool isComplete = false;
  String name;
  String? description = "";
  DateTime dueDate;
  //If you have time use RatingBar() for priority
  int priority;

  Task(
      {required this.name,
      this.description,
      required this.dueDate,
      required this.priority});
}

CodePudding user response：

The variable must be defined outside the body of the build method, otherwise it will be initialized when SetState.

class _TaskListState extends State<TaskList> {
  List<Task> userTaskList = [
    Task(name: "Spanish Hw", dueDate: DateTime.now(), priority: 1),
    Task(name: "Push Day", dueDate: DateTime.now(), priority: 3),
    Task(name: "English HL Essay", dueDate: DateTime.now(), priority: 2)
  ];

  @override
  Widget build(BuildContext context) {