lerp method Null safety

ShapeDecoration? lerp(
  1. ShapeDecoration? a,
  2. ShapeDecoration? b,
  3. double t

Linearly interpolate between two shapes.

Interpolates each parameter of the decoration separately.

If both values are null, this returns null. Otherwise, it returns a non-null value, with null arguments treated like a ShapeDecoration whose fields are all null (including the shape, which cannot normally be null).

The t argument represents position on the timeline, with 0.0 meaning that the interpolation has not started, returning a (or something equivalent to a), 1.0 meaning that the interpolation has finished, returning b (or something equivalent to b), and values in between meaning that the interpolation is at the relevant point on the timeline between a and b. The interpolation can be extrapolated beyond 0.0 and 1.0, so negative values and values greater than 1.0 are valid (and can easily be generated by curves such as Curves.elasticInOut).

Values for t are usually obtained from an Animation<double>, such as an AnimationController.

See also:


static ShapeDecoration? lerp(ShapeDecoration? a, ShapeDecoration? b, double t) {
  assert(t != null);
  if (a == null && b == null)
    return null;
  if (a != null && b != null) {
    if (t == 0.0)
      return a;
    if (t == 1.0)
      return b;
  return ShapeDecoration(
    color: Color.lerp(a?.color, b?.color, t),
    gradient: Gradient.lerp(a?.gradient, b?.gradient, t),
    image: t < 0.5 ? a!.image : b!.image, // TODO(ianh): cross-fade the image
    shadows: BoxShadow.lerpList(a?.shadows, b?.shadows, t),
    shape: ShapeBorder.lerp(a?.shape, b?.shape, t)!,