Widget _buildTabIndicator(
int tabIndex,
TabController tabController,
ColorTween selectedColorTween,
ColorTween previousColorTween)
{
Color background = null;
if (tabController.indexIsChanging)
{
float t = 1.0f - TabsUtils._indexChangeProgress(tabController);
if (tabController.index == tabIndex)
{
background = selectedColorTween.lerp(t);
}
else if (tabController.previousIndex == tabIndex)
{
background = previousColorTween.lerp(t);
}
else
{
background = selectedColorTween.begin;
}
}
else
{
float offset = tabController.offset;
if (tabController.index == tabIndex)
{
background = selectedColorTween.lerp(1.0f - offset.abs());
}
else if (tabController.index == tabIndex - 1 && offset > 0.0)
{
background = selectedColorTween.lerp(offset);
}
else if (tabController.index == tabIndex + 1 && offset < 0.0)
{
background = selectedColorTween.lerp(-offset);
}
else
{
background = selectedColorTween.begin;
}
}
return(new TabPageSelectorIndicator(
backgroundColor: background,
borderColor: selectedColorTween.end,
size: this.indicatorSize
));
}
public override void paint(Canvas canvas, Size size)
{
this._needsPaint = false;
this._painter = this._painter ?? this.indicator.createBoxPainter(this.markNeedsPaint);
if (this.controller.indexIsChanging)
{
Rect targetRect = this.indicatorRect(size, this.controller.index);
this._currentRect = Rect.lerp(targetRect, this._currentRect ?? targetRect,
TabsUtils._indexChangeProgress(this.controller));
}
else
{
int currentIndex = this.controller.index;
Rect previous = currentIndex > 0 ? this.indicatorRect(size, currentIndex - 1) : null;
Rect middle = this.indicatorRect(size, currentIndex);
Rect next = currentIndex < this.maxTabIndex ? this.indicatorRect(size, currentIndex + 1) : null;
float index = this.controller.index;
float value = this.controller.animation.value;
if (value == index - 1.0f)
{
this._currentRect = previous ?? middle;
}
else if (value == index + 1.0f)
{
this._currentRect = next ?? middle;
}
else if (value == index)
{
this._currentRect = middle;
}
else if (value < index)
{
this._currentRect = previous == null ? middle : Rect.lerp(middle, previous, index - value);
}
else
{
this._currentRect = next == null ? middle : Rect.lerp(middle, next, value - index);
}
}
D.assert(this._currentRect != null);
ImageConfiguration configuration = new ImageConfiguration(
size: this._currentRect.size
);
this._painter.paint(canvas, this._currentRect.topLeft, configuration);
}