titleTextStyle property Null safety
The default text style for the AppBar's title widget.
If this property is null, then AppBarTheme.titleTextStyle of ThemeData.appBarTheme is used. If that is also null, the default value is a copy of the overall theme's TextTheme.headline6 TextStyle, with color set to the app bar's foregroundColor.
This property is used to configure an AppBar.
final TextStyle? titleTextStyle;