1. override
void strokeGradient(GraphicsGradient gradient, double width, JointStyle jointStyle, CapsStyle capsStyle)

Source

@override
void strokeGradient(GraphicsGradient gradient, double width, JointStyle jointStyle, CapsStyle capsStyle) {
  // TODO: Currently strokeGradient is only supported in Canvas2D
  this.strokeColor(0xFFFF00FF, width, jointStyle, capsStyle);
}