trackOutlineWidth property
final
      The outline width of this Switch's track.
Resolved in the following states:
This example resolves the trackOutlineWidth based on the current
WidgetState of the Switch, providing a different outline width when it is
WidgetState.disabled.
  
    link
  
  Switch(
  value: true,
  onChanged: (bool value) { },
  trackOutlineWidth: WidgetStateProperty.resolveWith<double?>((Set<WidgetState> states) {
    if (states.contains(WidgetState.disabled)) {
      return 5.0;
    }
    return null; // Use the default width.
  }),
)
  Defaults to 2.0.
Implementation
final MaterialStateProperty<double?>? trackOutlineWidth;