finalExample.dart

transitionBuilder: (Widget child, Animation<double> animation) {
            final inAnimation =
                Tween<Offset>(begin: Offset(1.0, 0.0), end: Offset(0.0, 0.0))
                    .animate(animation);
            final outAnimation =
                Tween<Offset>(begin: Offset(-1.0, 0.0), end: Offset(0.0, 0.0))
                    .animate(animation);

            if (child.key == ValueKey(elapsed)) {
              return ClipRect(
                child: SlideTransition(
                  position: inAnimation,
                  child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: child,
                  ),
                ),
              );
            } else {
              return ClipRect(
                child: SlideTransition(
                  position: outAnimation,
                  child: Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: child,
                  ),
                ),
              );
            }
          },