No matter how many websites I visit and how many codes I copy, I still get a error in Android Studio when I am trying to create a basic Radio Button.

import 'package:flutter/material.dart';
void main() => runApp(MaterialApp(
  home: Home(),
));
class Home extends StatefulWidget {
  const Home({Key? key}) : super(key: key);
  @override
  State<Home> createState() => _HomeState();
}
class _HomeState extends State<Home> {
  @override
  int _value = 1;
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My Rent'),
      ),
      body: Column(
        children: [
          Radio(
            value: 1,
            groupValue: _value,
            onChanged: (value){
              setState(() {
                _value = value;
              });
            },
          ),
          Radio(
            value: 2,
            groupValue: _value,
            onChanged: (value){
              setState(() {
                _value = value;
              });
            },
          ),
          Radio(
            value: 3,
            groupValue: _value,
            onChanged: (value){
              setState(() {
                _value = value;
              });
            },
          ),
        ],
      ),
    );
  }
}

I don't know how to solve this, I have copied countless number of code in my compiler and nothing works related to Radio Buttons. Error is

lib/main.dart:43:26: Error: A value of type 'Object?' can't be assigned to a variable of type 'int'.
 - 'Object' is from 'dart:core'.
                _value = value;
                         ^

CodePudding user response：

You need to specify the type of Radio Button, here Radio widget as Radio<int> .

CodePudding user response：

The value parameter from onChanged is nullable. You can use bang operator if you are sure that value will never be null to make the compiler happy.

          Radio<int>(
            value: 2,
            groupValue: _value,
            onChanged: (value){
              setState(() {
                _value = value!;   // <--- use bang operator
              });
            },
          ),