How do I use hexadecimal color strings in Flutter?

385

votes

How do I convert a hexadecimal color string like #b74093 to a Color in Flutter?

I want to use a HEX color code in Dart.

in google chrome devtools you can quickly get the decimal numbers for a hex-style color; just click on the tiny color rectangle in the styles sidebar; in the popup you can switch the representation between HSLA, RGBA, HEX by clicking the chevron. Then you can use Color.fromRGBO() – ccpizza

572

votes

In Flutter the Color class only accepts integers as parameters, or there is the possibility to use the named constructors fromARGB and fromRGBO.

So we only need to convert the string #b74093 to an integer value. Also we need to respect that opacity always needs to be specified.
255 (full) opacity is represented by the hexadecimal value FF. This already leaves us with 0xFF. Now, we just need to append our color string like this:

const color = const Color(0xffb74093); // Second `const` is optional in assignments.

The letters can by choice be capitalized or not:

const color = const Color(0xFFB74093);

Starting with Dart 2.6.0, you can create an extension for the Color class that lets you use hexadecimal color strings to create a Color object:

extension HexColor on Color {
  /// String is in the format "aabbcc" or "ffaabbcc" with an optional leading "#".
  static Color fromHex(String hexString) {
    final buffer = StringBuffer();
    if (hexString.length == 6 || hexString.length == 7) buffer.write('ff');
    buffer.write(hexString.replaceFirst('#', ''));
    return Color(int.parse(buffer.toString(), radix: 16));
  }

  /// Prefixes a hash sign if [leadingHashSign] is set to `true` (default is `true`).
  String toHex({bool leadingHashSign = true}) => '${leadingHashSign ? '#' : ''}'
      '${alpha.toRadixString(16).padLeft(2, '0')}'
      '${red.toRadixString(16).padLeft(2, '0')}'
      '${green.toRadixString(16).padLeft(2, '0')}'
      '${blue.toRadixString(16).padLeft(2, '0')}';
}

The fromHex method could also be declared in a mixin or class because the HexColor name needs to be explicitly specified in order to use it, but the extension is useful for the toHex method, which can be used implicitly. Here is an example:

void main() {
  final Color color = HexColor.fromHex('#aabbcc');

  print(color.toHex());
  print(const Color(0xffaabbcc).toHex());
}

Disadvantage of using hex strings

Many of the other answers here show how you can dynamically create a Color from a hex string, like I did above. However, doing this means that the color cannot be a const.
Ideally, you would assign your colors the way I explained in the first part of this answer, which is more efficient when instantiating colors a lot, which is usually the case for Flutter widgets.

208

votes

The Color class expects an ARGB integer. Since you try to use it with an RGB value, represent it as int and prefix it with 0xff.

Color mainColor = Color(0xffb74093);

If you get annoyed by this and still wish to use strings, you can extend Color and add a string constructor

class HexColor extends Color {
  static int _getColorFromHex(String hexColor) {
    hexColor = hexColor.toUpperCase().replaceAll("#", "");
    if (hexColor.length == 6) {
      hexColor = "FF" + hexColor;
    }
    return int.parse(hexColor, radix: 16);
  }

  HexColor(final String hexColor) : super(_getColorFromHex(hexColor));
}

Usage

Color color1 = HexColor("b74093");
Color color2 = HexColor("#b74093");
Color color3 = HexColor("#88b74093"); // If you wish to use ARGB format

60

votes

If you want to use the hexadecimal code of a color which is in the format #123456, then it is very easy to do. Create a variable of type Color and assign the following values to it.

Color myHexColor = Color(0xff123456)

// Here you notice I use the 0xff and that is the opacity or transparency
// of the color and you can also change these values.

Use myhexcolor and you are ready to go.

If you want to change the opacity of color direct from the hexadecimal code, then change the ff value in 0xff to the respective value from the table below.

Hexadecimal opacity values

100% — FF

95% — F2

90% — E6

85% — D9

80% — CC

75% — BF

70% — B3

65% — A6

60% — 99

55% — 8C

50% — 80

45% — 73

40% — 66

35% — 59

30% — 4D

25% — 40

20% — 33

15% — 26

10% — 1A

5% — 0D

0% — 00

30

votes

How to use a hexadecimal color code #B74093 in Flutter

Simply remove the # sign from the hexadecimal color code and add 0xFF with the color code inside the Color class:

#b74093 will become Color(0xffb74093) in Flutter

#B74093 will become Color(0xFFB74093) in Flutter

Tthe ff or FF in Color(0xFFB74093) defines the opacity.

Hexadecimal colors example with all opacity types in Dartpad

25

votes

Easy way:

String color = yourHexColor.replaceAll('#', '0xff');

Usage:

Container(
    color: Color(int.parse(color)),
)

22

votes

To convert from a hexadecimal string to integer, do:

int hexToInt(String hex)
{
  int val = 0;
  int len = hex.length;
  for (int i = 0; i < len; i++) {
    int hexDigit = hex.codeUnitAt(i);
    if (hexDigit >= 48 && hexDigit <= 57) {
      val += (hexDigit - 48) * (1 << (4 * (len - 1 - i)));
    } else if (hexDigit >= 65 && hexDigit <= 70) {
      // A..F
      val += (hexDigit - 55) * (1 << (4 * (len - 1 - i)));
    } else if (hexDigit >= 97 && hexDigit <= 102) {
      // a..f
      val += (hexDigit - 87) * (1 << (4 * (len - 1 - i)));
    } else {
      throw new FormatException("Invalid hexadecimal value");
    }
  }
  return val;
}

Call example:

Color color = new Color(hexToInt("FFB74093"));

21

votes

A simple function without using a class:

Color _colorFromHex(String hexColor) {
  final hexCode = hexColor.replaceAll('#', '');
  return Color(int.parse('FF$hexCode', radix: 16));
}

You can use it like this:

Color color1 = _colorFromHex("b74093");
Color color2 = _colorFromHex("#b74093");

17

votes

There is another solution. If you store your color as a normal hexadecimal string and don't want to add opacity to it (leading "FF"):

Convert your hexadecimal string to int To convert a hexadecimal string to an integer, do one of the following:
```
 var myInt = int.parse(hexString, radix: 16);
```
or
```
 var myInt = int.parse("0x$hexString");
```
as a prefix of 0x (or -0x) will make int.parse default to a radix of 16.

Add opacity to your color via code

 Color color = new Color(myInt).withOpacity(1.0);

15

votes

Thanks for asking this question, simples solution is as:

// Color to Hex String

colorToHexString(Color color) {
  return '#FF${color.value.toRadixString(16).substring(2, 8)}';
}

// Hex String to Color

hexStringToColor(String hexColor) {
  hexColor = hexColor.toUpperCase().replaceAll("#", "");
  if (hexColor.length == 6) {
    hexColor = "FF" + hexColor;
  }
  return Color(int.parse(hexColor, radix: 16));
}

// How to call function

String hexCode = colorToHexString(Colors.green);
Color bgColor = hexStringToColor(hexCode);
print("$hexCode = $bgColor");

Enjoy code and help others :)

14

votes

This was the solution for me:

String hexString = "45a3df";
Color(int.parse("0xff${hexString}"));

It was the only way that didn't require additional steps.

11

votes

Use hexcolor for bringing hexadecimal colors to the Dart hexcolorPlugin:

hexcolor: ^2.0.3

Sample usage

import 'package:hexcolor/hexcolor.dart';
Container(
    decoration: new BoxDecoration(
        color: Hexcolor('#34cc89'),
    ),
    child: Center(
        child: Text(
            'Running on: $_platformVersion\n',
            style: TextStyle(color: Hexcolor("#f2f2f2")),
        ),
    ),
),

10

votes

You can use this

Color getColorFromColorCode(String code){
  return Color(int.parse(code.substring(1, 7), radix: 16) + 0xFF000000);
}

9

votes

File utils.dart

///
/// Convert a color hex-string to a Color object.
///
Color getColorFromHex(String hexColor) {
  hexColor = hexColor.toUpperCase().replaceAll('#', '');

  if (hexColor.length == 6) {
    hexColor = 'FF' + hexColor;
  }

  return Color(int.parse(hexColor, radix: 16));
}

Example usage

Text(
  'Hello, World!',
  style: TextStyle(
    color: getColorFromHex('#aabbcc'),
    fontWeight: FontWeight.bold,
  )
)

8

votes

In Flutter, to create a color from RGB with alpha, use:

return new Container(
  color: new Color.fromRGBO(0, 0, 0, 0.5),
);

How to use hexadecimal color:

return new Container(
  color: new Color(0xFF4286f4),
);
// 0xFF -> the opacity (FF for opaque)
// 4286f4 -> the hexadecimal color

Hexadecimal color with opacity:

return new Container(
  color: new Color(0xFF4286f4).withOpacity(0.5),
);

// Or change the "FF" value

100% — FF
 95% — F2
 90% — E6
 85% — D9
 80% — CC
 75% — BF
 70% — B3
 65% — A6
 60% — 99
 55% — 8C
 50% — 80
 45% — 73
 40% — 66
 35% — 59
 30% — 4D
 25% — 40
 20% — 33
 15% — 26
 10% — 1A
 5% — 0D
 0% — 00

For more, see the official documentation page, Color class - dart:ui library - Dart API.

8

votes

There isn't any need to use functions.

For example, to give a color to a container using colorcode:

Container
(
    color:Color(0xff000000)
)

Here the 0xff is the format followed by color code

6

votes

Add this function in your file -


Color parseColor(String color) {
  String hex = color.replaceAll("#", "");
  if (hex.isEmpty) hex = "ffffff";
  if (hex.length == 3) {
    hex = '${hex.substring(0, 1)}${hex.substring(0, 1)}${hex.substring(1, 2)}${hex.substring(1, 2)}${hex.substring(2, 3)}${hex.substring(2, 3)}';
  }
  Color col = Color(int.parse(hex, radix: 16)).withOpacity(1.0);
  return col;
}

And use it like -

Container(
    color: parseColor("#b74093")
)

6

votes

The easiest way is to convert it into an integer. For example, #BCE6EB. You would add 0xFF and you would then remove the hashtag making it:

0XFFBCE6EB

Then let’s say you were to implement it by doing:

backgroundColor: Color(0xffbce6eb)

If you can only use a hexadecimal then I suggest using the Hexcolor package.

5

votes

For general reference. There is a simpler way using the library Supercharged. Although you can use extension methods with all solutions mentioned, you find practical user library toolkit.

"#ff00ff".toColor(); // Painless hex to color
"red".toColor(); // Supports all web color names

Easier, right?

Supercharged

4

votes

"#b74093"? OK...

To HEX Recipe

int getColorHexFromStr(String colorStr)
{
  colorStr = "FF" + colorStr;
  colorStr = colorStr.replaceAll("#", "");
  int val = 0;
  int len = colorStr.length;
  for (int i = 0; i < len; i++) {
    int hexDigit = colorStr.codeUnitAt(i);
    if (hexDigit >= 48 && hexDigit <= 57) {
      val += (hexDigit - 48) * (1 << (4 * (len - 1 - i)));
    } else if (hexDigit >= 65 && hexDigit <= 70) {
      // A..F
      val += (hexDigit - 55) * (1 << (4 * (len - 1 - i)));
    } else if (hexDigit >= 97 && hexDigit <= 102) {
      // a..f
      val += (hexDigit - 87) * (1 << (4 * (len - 1 - i)));
    } else {
      throw new FormatException("An error occurred when converting a color");
    }
  }
  return val;
}

4

votes

As the Color constructor does not support hexadecimal string, so we should find other alternatives.

There are several possibilities:

1- The first one is to create a small function that will allow you to convert a color hex-string to a Color object.

Code:

   Color colorFromHex(String hexColor) {
   final hexCode = hexColor.replaceAll('#', '');
   if (hexColor.length == 6) {
    hexColor = 'FF' + hexColor; // FF as the opacity value if you don't add it.
   }
  return Color(int.parse('FF$hexCode', radix: 16));
}

Usage:

 Container(
          color: colorFromHex('abcdff'),
          child: Text(
            'Never stop learning',
            style: TextStyle(color: colorFromHex('bbffffcc')),
          ),
        )

2- The second possibility is to use the supercharged package. Supercharged brings all the comfort features from languages like Kotlin to all Flutter developers.

Add the dependency supercharged: ^1.X.X (find recent version) to your project and start using Supercharged everywhere:

import 'package:supercharged/supercharged.dart';

Now ,transform any String to colors

Code :

"#ff00ff".toColor(); // Painless hex to color
"red".toColor(); // Supports all web color names

You can also use the hexcolor package which is also great.

4

votes

Use hexadecimal numbers with the fromRGB constructor:

Color.fromRGBO(0xb7, 0x40, 0x93, 1),

3

votes

import 'package:flutter/material.dart';
class HexToColor extends Color{
  static _hexToColor(String code) {
    return int.parse(code.substring(1, 7), radix: 16) + 0xFF000000;
  }
  HexToColor(final String code) : super(_hexToColor(code));
}

Import the new class and use it like this:

HexToColor('#F2A03D')

3

votes

Unfortunately, the Color class constructor in Flutter does not accept a simple hexadecimal string (like #bfeb91 in CSS).

Instead, it requires an integer like 0xFFBFEB91.

So here we convert a hexadecimal string to an integer.

A simple function

Give this function a hexadecimal string and it will return you a Color!

Color _getColorFromHex(String hexColor) {
  hexColor = hexColor.replaceAll("#", "");
  if (hexColor.length == 6) {
    hexColor = "FF" + hexColor;
  }
  if (hexColor.length == 8) {
    return Color(int.parse("0x$hexColor"));
  }
}

Use it like this

Text(
  'Hello, World!',
  style: TextStyle(backgroundColor: _getColorFromHex('ff00aa')), // Or 'bfeb91', or 'ffbfeb91'
),

As a String extension

Leveraging the power of Dart extensions, we can augment String with a function that returns a Color:

extension ColorExtension on String {
  toColor() {
    var hexColor = this.replaceAll("#", "");
    if (hexColor.length == 6) {
      hexColor = "FF" + hexColor;
    }
    if (hexColor.length == 8) {
      return Color(int.parse("0x$hexColor"));
    }
  }
}

Use it like this:

Text(
  'Hello, World!',
  style: TextStyle(backgroundColor: '#bfeb91'.toColor()), // Or 'bfeb91', or 'ffbfeb91'
),

2

votes

You can click on Color Widget and it tells you with much deeper information what those letters stand for.

You can also use the Color.fromARGB() method to create custom colors which is much easier to me. Use the Flutter Doctor Color Picker website to pick any color you want for your Flutter application.

1

votes

You can use the package from_css_color to get Color out of a hexadecimal string. It supports both three-digit and six-digit RGB hexadecimal notation.

Color color = fromCSSColor('#ff00aa')

For optimisation sake, create a Color instance once for each color and store it somewhere for later usage.

0

votes

If you need a hexadecimal color desperately in your application, there is one simple step you can follow:

Convert your hexadecimal color into RGB format simply from here.
Get your RGB values.
In Flutter, you have an simple option to use RGB color:

Color.fromRGBO(r_value, g_value, b_value, opacity) will do the job for you.
Go ahead and tweak O_value to get the color you want.

0

votes

I have created this Flutter extention function of String class.. kinda useful if you also hate 0xFFF 😎

extension on String {
  Color parse() {
    var hexColor = this.replaceAll("#", "");
    if (hexColor.length == 6) {
      hexColor = "FF" + hexColor;
    }
    if (hexColor.length == 8) {
      return Color(int.parse("0x$hexColor"));
    }
  }
}

you can use to any hexadecimal color code string as follows...

'#bdbdbd'.parse() // this will return Color class object which you use in widget...

How do I use hexadecimal color strings in Flutter?

27 Answers

Disadvantage of using hex strings

Hexadecimal opacity values

File utils.dart

Example usage

To HEX Recipe