main.dart

AnimatedContainer(
                      duration: Duration(seconds: 1),
                      curve: Curves.fastOutSlowIn,
                      decoration: BoxDecoration(
                          borderRadius: BorderRadius.circular(15),
                          color: Colors.green),
                      width: (animationValue) * animationValue,
                      height: 50,
                      child: Center(
                        child: Text(
                          "Connected :)",
                          style: TextStyle(fontSize: 25, color: Colors.white),
                        ),
                      ),
                    ),