I have found a solution for this issue. We can catch the on tap event using a GlobalKey.

1. Define the global key

   final GlobalKey convexAppBarKey = GlobalKey();

2. Use convexAppBarKey as key of the ConvexAppBAr

   ConvexAppBar( key: convexAppBarKey, onTap: (index) { // Handle tab changes }, ),

3. Call the onTap event any where you want.

   ElevatedButton( onPressed: () { convexAppBarKey.currentState?.tap(1); }, child: Text("Tap Here"), )