Set Text Field value equal to double

I have a text field that inputs a number and want to set that value equal to a double, but whenever I try it does nothing and I am not sure why.

Below is how the textfield is implemented

TextField(
  keyboardType: TextInputType.number,
  controller: _incomeController,
  style: const TextStyle(
    color: Colors.black,
  ),
  decoration: const InputDecoration(
    filled: true,
    fillColor: Colors.white,
    hintText: 'Ba开发者_运维百科lance',
    hintStyle: TextStyle(color: Colors.grey),
    border: OutlineInputBorder(
      borderRadius: BorderRadius.all(
        Radius.circular(10.0),
      ),
      borderSide: BorderSide.none,
    ),
  ),
),

This is how I am trying to convert the text field to the double income.

income = _incomeController.text.trim() as double;

First seem like you are using wrong controller :

_balanceController instead of _incomeController

Second, you cannot cast string to double like that, instead try this:

income = double.tryParse(_balanceController.text.trim());

You must set TextField controller same. You are trying to get text from other TextEditingController. If you declared income nullable like that:

double? income;

You can convert to String like that:

income = double.tryParse(_balanceController.text.trim());
print(income is double);

And if text can't be converted to double then you get null, so print(income is double); will print false;

I created sample flutter application. Here you can see the whole code:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}
class MyWidget extends StatefulWidget {
  const MyWidget({Key? key});
  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  final _balanceController = TextEditingController();
  double? result;

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
      children: [
        Text("Result: $result"),
        TextField(
          keyboardType: TextInputType.number,
          controller: _balanceController,
          style: const TextStyle(
            color: Colors.black,
          ),
          decoration: const InputDecoration(
            filled: true,
            fillColor: Colors.white,
            hintText: 'Balance',
            hintStyle: TextStyle(color: Colors.grey),
            border: OutlineInputBorder(
              borderRadius: BorderRadius.all(
                Radius.circular(10.0),
              ),
              borderSide: BorderSide.none,
            ),
          ),
        ),
        OutlinedButton(
          onPressed: () {
            setState(() {
              result = double.tryParse(_balanceController.text.trim());
              print(result is double);
            });
          },
          child: const Text("Show result"),
        ),
      ],
    );
  }
}