SweepGradient class

A 2D sweep gradient.

This class is used by BoxDecoration to represent sweep gradients. This abstracts out the arguments to the ui.Gradient.sweep constructor from the dart:ui library.

A gradient has a center, a startAngle, and an endAngle. The startAngle corresponds to 0.0, and the endAngle corresponds to 1.0. These angles are expressed in radians.

The colors are described by a list of Color objects. There must be at least two colors. The stops list, if specified, must have the same length as colors. It specifies fractions of the vector from start to end, between 0.0 and 1.0, for each color. If it is null, a uniform distribution is assumed.

The region of the canvas before startAngle and after endAngle is colored according to tileMode.

Typically this class is used with BoxDecoration, which does the painting. To use a SweepGradient to paint on a canvas directly, see createShader.

Container(
  decoration: const BoxDecoration(
    gradient: SweepGradient(
      center: FractionalOffset.center,
      colors: <Color>[
        Color(0xFF4285F4), // blue
        Color(0xFF34A853), // green
        Color(0xFFFBBC05), // yellow
        Color(0xFFEA4335), // red
        Color(0xFF4285F4), // blue again to seamlessly transition to the start
      ],
      stops: <double>[0.0, 0.25, 0.5, 0.75, 1.0],
    ),
  )
)

Container(
  decoration: const BoxDecoration(
    gradient: SweepGradient(
      center: FractionalOffset.center,
      colors: <Color>[
        Color(0xFF4285F4), // blue
        Color(0xFF34A853), // green
        Color(0xFFFBBC05), // yellow
        Color(0xFFEA4335), // red
        Color(0xFF4285F4), // blue again to seamlessly transition to the start
      ],
      stops: <double>[0.0, 0.25, 0.5, 0.75, 1.0],
      transform: GradientRotation(math.pi/4),
    ),
  ),
)

See also:

• LinearGradient, which displays a gradient in parallel lines, and has an example which shows a different way to use Gradient objects.
• RadialGradient, which displays a gradient in concentric circles, and has an example which shows a different way to use Gradient objects.
• BoxDecoration, which can take a SweepGradient in its BoxDecoration.gradient property.