Flutter Question posted in
The official Flutter documentation can be found here.

Flutter – Why Can't Display Double on Text Widget

I have been trying to display a double variable on a Text Widget but I keep getting this error message:

Error: Method invocation is not a constant expression. bid.toString()

I tried the toString() and even using the $bid yet it still didn’t work. What is the best way to display Int or Double on Text widgets

What could be the reason I can’t display a double or int on a text widget?
Here is my code:

import 'dart:math';
import 'package:flutter/material.dart';

class BuyXSO extends StatefulWidget {
 const BuyXSO({super.key});

 @override
 State<BuyXSO> createState() => _BuyXSOState();
}

class _BuyXSOState extends State<BuyXSO> {
 double bid = roundNumber(1.324, 2);
 double offer = roundNumber((2.75, 2);

 double roundNumber(double value, int places) {
  num val = pow(10.0, places);
  return ((value * val).round().toDouble() / val);
 }

@override
Widget build(BuildContext context) {
 return Column(
     children: [

      //XSO Ticker
      Padding(
        padding: const EdgeInsets.all(15.0),
        child: Container(
          padding: EdgeInsets.all(15.0),
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(5),
            border: Border.all(color: const Color.fromARGB(255, 218, 216, 216)),
          ),

          child: const SizedBox(
            height: 50,
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Row(
                  children: [
                    Text('XSocial',
                      style: TextStyle(fontSize: 18),
                    ),
                    Text(' XSO',
                      style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold,),
                    ),
                  ],
                ),
            
                VerticalDivider(
                  color: Color.fromARGB(255, 218, 216, 216),
                  thickness: 1,
                ),
            
                Column(
                  children: [
                    Text('BID',
                      style: TextStyle(fontSize: 12, color: Colors.black54),
                    ),
                    Text(
                      bid.toString(),
                      style: TextStyle(
                        fontSize: 18,
                        fontWeight: FontWeight.bold,
                        color: const Color.fromARGB(255, 2, 160, 68),
                      ),
                    ),
                  ],
                ),

                VerticalDivider(
                  color: Color.fromARGB(255, 218, 216, 216),
                  thickness: 1,
                ),
                
                Column(
                  children: [
                    Text('OFFER',
                      style: TextStyle(fontSize: 12, color: Colors.black54),
                    ),
                    Text(
                      offer.toString(),
                      style: TextStyle(
                        fontSize: 18,
                        fontWeight: FontWeight.bold,
                        color: const Color.fromARGB(255, 2, 160, 68),
                      ),
                    ),
                  ],
                ),
              ],
            ),
          ),
        ),
      ),


    ],

  );
 }
}
Tags:

2

Answers


  1. 0

    I think there are two problems. You have to declare the roundNumber method before you can use it, so you need to move your use of it into the _BuyXSOState.build override:

    ...
class _BuyXSOState extends State<BuyXSO> {

  double roundNumber(double value, int places) {
  num val = pow(10.0, places);
  return ((value * val).round().toDouble() / val);
 }

@override
Widget build(BuildContext context) {
  double  bid = roundNumber(1.324, 2),
          offer = roundNumber(2.75,2);

 return Column(
     children: [
...

    Then you might want to review this answer to get the dynamic content into the column, because it doesn’t appear that you can dynamically declare the text like you’re trying to do: How to add the widgets dynamically to column in Flutter?

    Does this help?

    Login or Signup to reply.
  2. 0

    Two problems are found here.

    1. You can’t call a method in the same scope while declaring it.
    2. You can’t define the parent widget as const while it contains non-const valued children. Ex. bid is not a const.

    Solution:

    1. Declare bid with a value.
    2. Call roundNumber() in initState() and assign value to bid
    3. Remove const from SizedBox

    Here is the updated code:

    import 'dart:math';
import 'package:flutter/material.dart';

class BuyXSO extends StatefulWidget {
  const BuyXSO({super.key});

  @override
  State<BuyXSO> createState() => _BuyXSOState();
}

class _BuyXSOState extends State<BuyXSO> {
  double bid = 0;
  double offer = 0;

  double roundNumber(double value, int places) {
    num val = pow(10.0, places);
    return ((value * val).round().toDouble() / val);
  }

  @override
  void initState() {
    bid = roundNumber(1.324, 2);
    offer = roundNumber(2.75, 2);

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        //XSO Ticker
        Padding(
          padding: const EdgeInsets.all(15.0),
          child: Container(
            padding: EdgeInsets.all(15.0),
            decoration: BoxDecoration(
              borderRadius: BorderRadius.circular(5),
              border: Border.all(color: const Color.fromARGB(255, 218, 216, 216)),
            ),

            //change here
            child: SizedBox(
              height: 50,
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: [
                  Row(
                    children: [
                      Text(
                        'XSocial',
                        style: TextStyle(fontSize: 18),
                      ),
                      Text(
                        ' XSO',
                        style: TextStyle(
                          fontSize: 18,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
                    ],
                  ),
                  VerticalDivider(
                    color: Color.fromARGB(255, 218, 216, 216),
                    thickness: 1,
                  ),
                  Column(
                    children: [
                      Text(
                        'BID',
                        style: TextStyle(fontSize: 12, color: Colors.black54),
                      ),
                      Text(
                        bid.toString(),
                        style: TextStyle(
                          fontSize: 18,
                          fontWeight: FontWeight.bold,
                          color: const Color.fromARGB(255, 2, 160, 68),
                        ),
                      ),
                    ],
                  ),
                  VerticalDivider(
                    color: Color.fromARGB(255, 218, 216, 216),
                    thickness: 1,
                  ),
                  Column(
                    children: [
                      Text(
                        'OFFER',
                        style: TextStyle(fontSize: 12, color: Colors.black54),
                      ),
                      Text(
                        offer.toString(),
                        style: TextStyle(
                          fontSize: 18,
                          fontWeight: FontWeight.bold,
                          color: const Color.fromARGB(255, 2, 160, 68),
                        ),
                      ),
                    ],
                  ),
                ],
              ),
            ),
          ),
        ),
      ],
    );
  }
}

    #Output
    enter image description here

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search