tabBar property Null safety
The CupertinoTabBar.currentIndex is only used to initialize a CupertinoTabController when no controller is provided. Subsequently providing a different CupertinoTabBar.currentIndex does not affect the scaffold or the tab bar's active tab index. To programmatically change the active tab index, use a CupertinoTabController.
If CupertinoTabBar.onTap is provided, it will still be called.
CupertinoTabScaffold automatically also listen to the
onTap to change the controller's
and change the actively displayed tab in CupertinoTabScaffold's own
main content area.
If translucent, the main content may slide behind it. Otherwise, the main content's bottom margin will be offset by its height.
tabBar has its text scale factor set to 1.0 and does not
respond to text scale factor changes from the operating system, to match
the native iOS behavior. To override this behavior, wrap each of the
items inside a MediaQuery with the desired MediaQueryData.textScaleFactor
value. The text scale factor value from the operating system can be retrieved
int many ways, such as querying MediaQuery.textScaleFactorOf against
Must not be null.
final CupertinoTabBar tabBar;