UnderlineTabIndicator

在选中标签下方绘制一条水平线。

配合 indicator 使用，可自定义指示线的 内边距（insets）以及可选的边角圆角半径。

属性

名称	类型	默认值	说明
border_side	BorderSide	BorderSide(width=2.0()	The color and weight of the horizontal line drawn below the selected tab.
insets	PaddingValue	Padding.zero(()	Locates the selected tab's underline relative to the tab's boundary. The indicator_size property can be used to define the tab indicator's bounds in terms of its (centered) tab control with LABEL, or the entire tab with TAB.
border_radius	Optional[BorderRadiusValue]	None	The radius of the indicator's corners. If this value is not None, a rounded rectangular tab indicator is drawn, otherwise rectangular tab indicator is drawn.