lerpTo method Null safety
- ShapeBorder? b,
- double t
Linearly interpolates from this
to another ShapeBorder (possibly of
another class).
This is called if b
's lerpTo did not know how to handle this class.
When implementing this method in subclasses, return null if this class
cannot interpolate from b
. In that case, lerp will apply a default
behavior instead. If b
is null, this must not return null.
The base class implementation handles the case of b
being null by
deferring to scale.
The t
argument represents position on the timeline, with 0.0 meaning
that the interpolation has not started, returning this
(or something
equivalent to this
), 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 this
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.
Instead of calling this directly, use ShapeBorder.lerp.
Implementation
@override
ShapeBorder? lerpTo(ShapeBorder? b, double t) {
if (t == 0) {
return this;
}
if (t == 1.0) {
return b;
}
if (b is StarBorder) {
return StarBorder(
side: BorderSide.lerp(side, b.side, t),
points: ui.lerpDouble(points, b.points, t)!,
rotation: ui.lerpDouble(_rotationRadians, b._rotationRadians, t)! * _kRadToDeg,
innerRadiusRatio: ui.lerpDouble(innerRadiusRatio, b.innerRadiusRatio, t)!,
pointRounding: ui.lerpDouble(pointRounding, b.pointRounding, t)!,
valleyRounding: ui.lerpDouble(valleyRounding, b.valleyRounding, t)!,
squash: ui.lerpDouble(squash, b.squash, t)!,
);
}
if (b is CircleBorder) {
// Have a slightly different lerp for two-pointed stars, since they get
// kind of squirrelly with near-zero innerRadiusRatios.
if (points >= 2.5) {
final double lerpedPoints = ui.lerpDouble(points, points.round(), t)!;
return StarBorder(
side: BorderSide.lerp(side, b.side, t),
points: lerpedPoints,
squash: ui.lerpDouble(squash, b.eccentricity, t)!,
rotation: rotation,
innerRadiusRatio: ui.lerpDouble(innerRadiusRatio, math.cos(math.pi / lerpedPoints), t)!,
pointRounding: ui.lerpDouble(pointRounding, 1.0, t)!,
valleyRounding: ui.lerpDouble(valleyRounding, 0.0, t)!,
);
} else {
final double lerpedPoints = ui.lerpDouble(points, 2, t)!;
return StarBorder(
side: BorderSide.lerp(side, b.side, t),
points: lerpedPoints,
squash: ui.lerpDouble(squash, b.eccentricity, t)!,
rotation: rotation,
innerRadiusRatio: ui.lerpDouble(innerRadiusRatio, 1, t)!,
pointRounding: ui.lerpDouble(pointRounding, 0.5, t)!,
valleyRounding: ui.lerpDouble(valleyRounding, 0.5, t)!,
);
}
}
if (b is StadiumBorder) {
// Lerp to a circle first, then to a stadium.
final BorderSide lerpedSide = BorderSide.lerp(side, b.side, t);
return _twoPhaseLerp(
t,
0.5,
(double t) => lerpTo(CircleBorder(side: lerpedSide), t),
(double t) => b.lerpFrom(CircleBorder(side: lerpedSide), t),
);
}
if (b is RoundedRectangleBorder) {
// Lerp to a circle, and then to a stadium, then to a rounded rect.
final BorderSide lerpedSide = BorderSide.lerp(side, b.side, t);
return _twoPhaseLerp(
t,
2 / 3,
(double t) {
return _twoPhaseLerp(
t,
0.5,
(double t) => lerpTo(CircleBorder(side: lerpedSide), t),
(double t) => StadiumBorder(side: lerpedSide).lerpFrom(CircleBorder(side: lerpedSide), t),
);
},
(double t) {
return StadiumBorder(side: lerpedSide).lerpTo(b, t);
},
);
}
return super.lerpTo(b, t);
}