SweepGradient class Null safety

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.

link
This sample draws a different color in each quadrant. 
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],
    ),
  )
)

link
This sample takes the above gradient and rotates it by math.pi/4 radians, i.e. 45 degrees. 
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:

Inheritance

Constructors

SweepGradient({AlignmentGeometry center = Alignment.center, double startAngle = 0.0, double endAngle = math.pi * 2, required List<Color> colors, List<double>? stops, TileMode tileMode = TileMode.clamp, GradientTransform? transform})
Creates a sweep gradient.
const

Properties

center → AlignmentGeometry
The center of the gradient, as an offset into the (-1.0, -1.0) x (1.0, 1.0) square describing the gradient which will be mapped onto the paint box.
final
colors → List<Color>
The colors the gradient should obtain at each of the stops.
finalinherited
endAngle → double
The angle in radians at which stop 1.0 of the gradient is placed.
final
hashCode → int
The hash code for this object.
read-onlyoverride
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited
startAngle → double
The angle in radians at which stop 0.0 of the gradient is placed.
final
stops → List<double>?
A list of values from 0.0 to 1.0 that denote fractions along the gradient.
finalinherited
tileMode → TileMode
How this gradient should tile the plane beyond in the region before startAngle and after endAngle.
final
transform → GradientTransform?
The transform, if any, to apply to the gradient.
finalinherited

Methods

createShader(Rect rect, {TextDirection? textDirection}) → Shader
Creates a Shader for this gradient to fill the given rect.
override
lerpFrom(Gradient? a, double t) → Gradient?
Linearly interpolates from another Gradient to this.
override
lerpTo(Gradient? b, double t) → Gradient?
Linearly interpolates from this to another Gradient.
override
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed.
inherited
scale(double factor) → SweepGradient
Returns a new SweepGradient with its colors scaled by the given factor.
override
toString() → String
A string representation of this object.
override

Operators

operator ==(Object other) → bool
The equality operator.
override

Static Methods

lerp(SweepGradient? a, SweepGradient? b, double t) → SweepGradient?
Linearly interpolate between two SweepGradients.
override