I'm making a Todolist as first project with flutter and now I have this error:

Problem 1

type 'int' is not a subtype of type 'String'

Problem 2

I have also problem with line: 18

in the tutorial he says: List todos = List(); but this isn't working

My code:

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
    theme: ThemeData(
        brightness: Brightness.light,
        primaryColor: Colors.blue,
        colorScheme: ColorScheme.fromSwatch().copyWith(secondary: Colors.orange)
    ),
    home: const TodoApp()
));
class TodoApp extends StatefulWidget{
  const TodoApp({Key? key}) : super(key: key);

  @override
  _TodoState createState() => _TodoState();
}
class _TodoState extends State<TodoApp>{
  List todos = List.filled(3, 0, growable: true);

  void initSate(){
    super.initState();
    todos.add("Item1");
    todos.add("Item2");
    todos.add("Item3");
    todos.add("Item4");
  }

  @override
  Widget build(BuildContext context){
    return Scaffold(
      appBar: AppBar(
        title: const Text("TodoApp"),
      ),
      body: ListView.builder(
          itemCount: todos.length,
          itemBuilder: (BuildContext context, int index){
            return Dismissible(
                key: Key(todos[index]),
                child: Card(
                  child: ListTile(
                    title: Text(todos[index]),
                  ),
                ));
          }),
    );
  }
}

I would like to learn something. Thank you for helping :)

CodePudding user response：

Try below code hope its helpful to you. use toString() for index

ListView.builder(
      itemCount: todos.length,
      itemBuilder: (BuildContext context, int index) {
        return Dismissible(
          key: Key(
            todos[index].toString(),
          ),
          child: Card(
            child: ListTile(
              title: Text(
                todos[index].toString(),
              ),
            ),
          ),
        );
      }),

Your result screen->

CodePudding user response：

The problem is simply because you're incorrectly initialized your variables with:

List todos = List.filled(3, 0, growable: true);

which will initialized your variables with integer.

The same problem could be easily avoided in the future by creating your list with specific type, like List<String>.

So, change your code to the following:

// Using dynamic list
List todos = List.filled(3, "", growable: true);
// this will initialized todos => ["", "", ""]

or

// use list string  
List<String> todos = List.filled(3, "", growable: true);
// this will initialized todos => ["", "", ""]

When removing item with dismissable, you need to add onDismissed property for Dismissable.

Here the complete working code with all the errors corrected:

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
    theme: ThemeData(
        brightness: Brightness.light,
        primaryColor: Colors.blue,
        colorScheme:
            ColorScheme.fromSwatch().copyWith(secondary: Colors.orange)),
    home: const TodoApp()));

class TodoApp extends StatefulWidget {
  const TodoApp({Key? key}) : super(key: key);

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

class _TodoState extends State<TodoApp> {
  //List<String> todos = List.filled(0, "", growable: true);
  // Use empty list instead List.filled
  List<String> todos = [];

  // Need to override initState to adding items.
  @override
  void initState() {
    todos.add("Item1");
    todos.add("Item2");
    todos.add("Item3");
    todos.add("Item4");
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("TodoApp"),
      ),
      body: ListView.builder(
          itemCount: todos.length,
          itemBuilder: (BuildContext context, int index) {
            // use item for each todo by index.
            final item = todos[index];
            return Dismissible(
                
                // Add onDismissed property to properly delete an item
                onDismissed: (direction) {
                  // Remove the item from the data source.
                  setState(() {
                    todos.removeAt(index);
                  });

                  // Then show a snackbar.
                  ScaffoldMessenger.of(context)
                      .showSnackBar(SnackBar(content: Text('$item dismissed')));
                },
                key: Key(item),
                child: Card(
                  child: ListTile(
                    title: Text(item),
                  ),
                ));
          }),
    );
  }
}

Result:

See https://api.dart.dev/stable/2.14.4/dart-core/List/List.filled.html for details.