public override Simulation createBallisticSimulation(ScrollMetrics position, double velocity)
{
Tolerance tolerance = this.tolerance;
if (position.outOfRange())
{
double?end = null;
if (position.pixels > position.maxScrollExtent)
{
end = position.maxScrollExtent;
}
if (position.pixels < position.minScrollExtent)
{
end = position.minScrollExtent;
}
D.assert(end != null);
return(new ScrollSpringSimulation(
this.spring,
position.pixels,
position.maxScrollExtent,
Math.Min(0.0, velocity),
tolerance: tolerance
));
}
if (velocity.abs() < tolerance.velocity)
{
return(null);
}
if (velocity > 0.0 && position.pixels >= position.maxScrollExtent)
{
return(null);
}
if (velocity < 0.0 && position.pixels <= position.minScrollExtent)
{
return(null);
}
return(new ClampingScrollSimulation(
position: position.pixels,
velocity: velocity,
tolerance: tolerance
));
}
public override Simulation createBallisticSimulation(ScrollMetrics position, float velocity)
{
Tolerance tolerance = this.tolerance;
if (velocity.abs() >= tolerance.velocity || position.outOfRange())
{
return(new BouncingScrollSimulation(
spring: this.spring,
position: position.pixels,
velocity: velocity * 0.91f,
leadingExtent: position.minScrollExtent,
trailingExtent: position.maxScrollExtent,
tolerance: tolerance
));
}
return(null);
}
public override double applyPhysicsToUserOffset(ScrollMetrics position, double offset)
{
D.assert(position.minScrollExtent <= position.maxScrollExtent);
if (!position.outOfRange())
{
return(offset);
}
double overscrollPastStart = Math.Max(position.minScrollExtent - position.pixels, 0.0);
double overscrollPastEnd = Math.Max(position.pixels - position.maxScrollExtent, 0.0);
double overscrollPast = Math.Max(overscrollPastStart, overscrollPastEnd);
bool easing = (overscrollPastStart > 0.0 && offset < 0.0) || (overscrollPastEnd > 0.0 && offset > 0.0);
double friction = easing
? this.frictionFactor((overscrollPast - offset.abs()) / position.viewportDimension)
: this.frictionFactor(overscrollPast / position.viewportDimension);
double direction = offset.sign();
return(direction * _applyFriction(overscrollPast, offset.abs(), friction));
}
public override float applyPhysicsToUserOffset(ScrollMetrics position, float offset)
{
D.assert(offset != 0.0);
D.assert(position.minScrollExtent <= position.maxScrollExtent);
if (!position.outOfRange())
{
return(offset);
}
var overScrollPastStart = Math.Max(position.minScrollExtent - position.pixels, 0.0f);
var overScrollPastEnd = Math.Max(position.pixels - position.maxScrollExtent, 0.0f);
var overScrollPast = Mathf.Max(overScrollPastStart, overScrollPastEnd);
bool easing = (overScrollPastStart > 0.0 && offset < 0.0) ||
(overScrollPastEnd > 0.0 && offset > 0.0);
var friction = easing
? frictionFactor(
(overScrollPast - offset.abs()) / position.viewportDimension)
: frictionFactor(overScrollPast / position.viewportDimension);
float direction = offset.sign();
return(direction * _applyFriction(overScrollPast, offset.abs(), friction));
}
