Question 127089 in Android Studio Question posted in
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Android Studio – Errors trying to create a notes app (Flutter)

I’m new to stack overflow so feel free to let me know anything that I am missing to include that will help you all in solving my issue.

I am creating a basic notes application on Android Studio using Dart and Flutter.
The issues that I am running into are

  • I keep getting a red error screen that says "Type ‘init’ is not a subtype of type ‘string’"
  • As well as to when I try to do ‘List todo = List();’ I get "The default ‘List’ constructor isn’t available when null safety is enabled."

I’ve been trying to resolve this issue, but been stuck/have been struggling with it for a while now. Was hoping on any advice/how to go about this issue.

Here is my Code, any help is much appreciated:

import 'dart:ffi';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:units/main.dart';
import '../views/dreams_view.dart';
import '../presenter/dreams_presenter.dart';
import 'home_screen.dart';

class Log_Page extends StatefulWidget {
  final UNITSPresenter presenter;

  Log_Page(this.presenter, {required Key? key, required this.title}) : super(key: key);
  final String title;

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

void main ()=> runApp(MyApp());


class _LogPageState extends State<Log_Page> {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
        home: Home(),
        debugShowCheckedModeBanner: false,
        theme: ThemeData(
            primaryColor: Color(0xff2B2D2D),
            scaffoldBackgroundColor: Color(0xff2B2D2D)
        )
    );
  }
}

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();

}

class _HomeState extends State<Home> {
  String input = " ";
  List todo = List(); //todo = diary/log


  //void initState (){
    //todo.add("cycle");
    //super.initState();
  //}


  @override
  Widget build (BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
          elevation: 0.0,
          centerTitle: true,
          title: Text("Diary/Log",
            style: TextStyle(
              color: Colors.white,
              fontSize: 35,
              fontStyle: FontStyle.italic,
              letterSpacing: 2,
            ),
          ),
        ),
        floatingActionButton: FloatingActionButton(
          backgroundColor: Colors.white,
          child: Icon(Icons.add,color: Colors.red [500],size: 35, ),
          onPressed: (){
            showDialog (
                context: context,
                builder: (BuildContext context){
                  return AlertDialog(
                    //backgroundColor: Color(0xffF48C8C),
                    title: Text("Add Diary/Log"),
                    content: TextField(
                      decoration: InputDecoration(
                          hintText: "Diary/Log"
                      ),
                      onChanged: (String value){
                        input = value;

                      },
                    ),
                    actions: [
                      FlatButton(
                          onPressed: ()
                          {
                            setState(() {
                              todo.add(input);
                            });
                            Navigator.of(context).pop();
                          },
                          child: Text("Add",style: TextStyle(color: Colors.black),)
                      )
                    ],
                  );
                });

          },
        ),
        body: Padding (
          padding: EdgeInsets.all(5),
          child: ListView.builder(
              itemCount: todo.length,
              itemBuilder: (BuildContext context,int index){
                return Dismissible(
                    key: Key(todo[index]),
                    child: Card(
                      elevation: 4,
                      margin: EdgeInsets.all(8),
                      shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(16),

                      ),
                      child: ListTile(
                        title: Text(todo[index],
                          style: TextStyle(
                            color: Colors.black,
                          ),),
                        trailing: IconButton(
                          icon: Icon(Icons.delete_forever_rounded, color: Colors.red,),
                          onPressed: ()
                          {
                            setState(() {
                              todo.removeAt(index);
                            });
                          },
                        ),
                      ) ,
                    )
                );
              }
          ),
        ),
      ),
    );
  }
}

Wanted a simple notes application/page.

Tags:

3

Answers


  1. 0

    Try to specify the list type and it is recommended to initialize empty list with [] because initialize with List() is deprecated.

    List<String> todo = [];
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  2. 0

    You declared your array incorrectly, try this

    List<String> todo = [];
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  3. 0

    So the problem in your code is that you wanted to initialize a List for which you used this code:

    List todo = List();

    what you did was you constructed the class of list. In order to declare the list you just have to write :

    List todo = [];

    if you want to use the previous method you need to keep in mind that This constructor cannot be used in null-safe code. Use List.filled to create a non-empty list. This requires a fill value to initialize the list elements with. To create an empty list, use [] for a growable list or List.empty for a fixed length list (or where growability is determined at run-time).

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