ListWheelViewport constructor

const ListWheelViewport({Key key, double diameterRatio: RenderListWheelViewport.defaultDiameterRatio, double perspective: RenderListWheelViewport.defaultPerspective, double offAxisFraction: 0.0, bool useMagnifier: false, double magnification: 1.0, @required double itemExtent, bool clipToSize: true, bool renderChildrenOutsideViewport: false, @required ViewportOffset offset, @required ListWheelChildDelegate childDelegate })

Creates a viewport where children are rendered onto a wheel.

The diameterRatio argument defaults to 2.0 and must not be null.

The perspective argument defaults to 0.003 and must not be null.

The itemExtent argument in pixels must be provided and must be positive.

The clipToSize argument defaults to true and must not be null.

The renderChildrenOutsideViewport argument defaults to false and must not be null.

The offset argument must be provided and must not be null.

Implementation 

const ListWheelViewport({
  Key key,
  this.diameterRatio = RenderListWheelViewport.defaultDiameterRatio,
  this.perspective = RenderListWheelViewport.defaultPerspective,
  this.offAxisFraction = 0.0,
  this.useMagnifier = false,
  this.magnification = 1.0,
  @required this.itemExtent,
  this.clipToSize = true,
  this.renderChildrenOutsideViewport = false,
  @required this.offset,
  @required this.childDelegate,
}) : assert(childDelegate != null),
     assert(offset != null),
     assert(diameterRatio != null),
     assert(diameterRatio > 0, RenderListWheelViewport.diameterRatioZeroMessage),
     assert(perspective != null),
     assert(perspective > 0),
     assert(perspective <= 0.01, RenderListWheelViewport.perspectiveTooHighMessage),
     assert(itemExtent != null),
     assert(itemExtent > 0),
     assert(clipToSize != null),
     assert(renderChildrenOutsideViewport != null),
     assert(
       !renderChildrenOutsideViewport || !clipToSize,
       RenderListWheelViewport.clipToSizeAndRenderChildrenOutsideViewportConflict,
     ),
     super(key: key);