public override void paint(PaintingContext context, Offset offset)
{
List <RenderBox> children = getChildrenAsList();
// Paint thumb if highlightedIndex is not null.
if (highlightedIndex != null)
{
if (_childAnimations == null)
{
_childAnimations = new Dictionary <RenderBox, _ChildAnimationManifest>();//<RenderBox, _ChildAnimationManifest> { };
for (int i = 0; i < childCount - 1; i += 1)
{
bool shouldFadeOut = i == highlightedIndex || i == highlightedIndex - 1;
RenderBox child = children[i];
_childAnimations[child] = new _ChildAnimationManifest(separatorOpacity: shouldFadeOut ? 0 : 1);
}
}
RenderBox selectedChild = children[highlightedIndex ?? 0];
_SlidingSegmentedControlContainerBoxParentData childParentData =
selectedChild.parentData as _SlidingSegmentedControlContainerBoxParentData;
Rect unscaledThumbTargetRect = CupertinoSlidingSegmentedControlsUtils._kThumbInsets.inflateRect(childParentData.offset & selectedChild.size);
// Update related Tweens before animation update phase.
if (_needsThumbAnimationUpdate)
{
// Needs to ensure _currentThumbRect is valid.
_currentThumbTween = new RectTween(begin: currentThumbRect ?? unscaledThumbTargetRect, end: unscaledThumbTargetRect);
for (int i = 0; i < childCount - 1; i += 1)
{
bool shouldFadeOut = i == highlightedIndex || i == highlightedIndex - 1;
RenderBox child = children[i];
_ChildAnimationManifest manifest = _childAnimations[child];
D.assert(manifest != null);
manifest.separatorTween = new FloatTween(
begin: manifest.separatorOpacity,
end: shouldFadeOut ? 0 : 1
);
}
_needsThumbAnimationUpdate = false;
}
else if (_currentThumbTween != null && unscaledThumbTargetRect != _currentThumbTween.begin)
{
_currentThumbTween = new RectTween(begin: _currentThumbTween.begin, end: unscaledThumbTargetRect);
}
for (int index = 0; index < childCount - 1; index += 1)
{
_paintSeparator(context, offset, children[index]);
}
currentThumbRect = _currentThumbTween?.evaluate(state.thumbController)
?? unscaledThumbTargetRect;
currentThumbScale = _thumbScaleTween.evaluate(state.thumbScaleController);
Rect thumbRect = Rect.fromCenter(
center: currentThumbRect.center,
width: currentThumbRect.width * currentThumbScale,
height: currentThumbRect.height * currentThumbScale
);
_paintThumb(context, offset, thumbRect);
}
else
{
// Reset all animations when there"s no thumb.
currentThumbRect = null;
_childAnimations = null;
for (int index = 0; index < childCount - 1; index += 1)
{
_paintSeparator(context, offset, children[index]);
}
}
for (int index = 0; index < children.Count; index++)
{
_paintChild(context, offset, children[index], index);
}
}