How can i use random color in colors array(not in single color) in flutter-CodePudding

If we need a random color for single color, There are lot of methods like

 color: Color(Random().nextInt(0xffffffff)).withAlpha(0xff);
 color: Colors.primaries[Random().nextInt(Colors.primaries.length)],
 color: Colors.primaries[Random().nextInt(Colors.primaries.length)],

If i use the above color code in colors array it shows error,

but i want to use random color in colors array

like

              colors: <Color>[
                      randomColor,
                      randomColor,
                      randomColor,
                    ],

My full code

 Ink(
                decoration: const BoxDecoration(
                  gradient: LinearGradient(
                    colors: <Color>[
                      Colors.blue,
                      Colors.red,
                      Colors.green,
                    ],
                  ),
                  borderRadius: BorderRadius.all(Radius.circular(80.0)),
                ),
),

Please help someone. Thanks in advance.

CodePudding user response：

The colors you defined are not constant

 color: Color(Random().nextInt(0xffffffff)).withAlpha(0xff);
 color: Colors.primaries[Random().nextInt(Colors.primaries.length)],
 color: Colors.primaries[Random().nextInt(Colors.primaries.length)],

That's why you get the error in LinearGradient since you declared your BoxDecoration as constant.

Evaluation of this constant expression throws an exception

To fix your issue just omit the const right before BoxDecoration.

Ink(
          decoration: BoxDecoration(
            gradient: LinearGradient(
              colors: <Color>[
                randomColor,
                randomColor,
                randomColor,
              ],
            ),
            borderRadius: const BorderRadius.all(Radius.circular(80.0)),
          ),
        ),

CodePudding user response：

You can do as below

final List<Color> colorCollection = <Color>[];

@override
void initState() {
  super.initState();
  addColorToArray();
}



void addColorToArray() { //Here you can add color as your requirement and call it in initState
    colorCollection.add(Colors.green);
    colorCollection.add(Colors.black);
    colorCollection.add(Colors.green);
    colorCollection.add(Colors.black);
    colorCollection.add(Colors.green);
    colorCollection.add(Colors.black);
    colorCollection.add(Colors.green);
    colorCollection.add(Colors.black);
    colorCollection.add(Colors.green);
  }

Use it as below where you want to put random color

color: colorCollection[random.nextInt(9)]

Ink(
                decoration: const BoxDecoration(
                  gradient: LinearGradient(
                    colors: colorCollection[random.nextInt(9)],
                  ),
                  borderRadius: BorderRadius.all(Radius.circular(80.0)),
                ),
),

Hope it's work for you