labelStyle property

Customizes the data label text style.

Using the TextStyle, add style data labels.

Defaults to the TextStyle property with font size 12.0 and font family Roboto.

Also refer TextStyle.

@override
Widget build(BuildContext context) {
 return Scaffold(
   body: Center(
       child: SfSparkLineChart(
         labelStyle: TextStyle(fontStyle: FontStyle.italic)
      )
    ),
 );
}