1. define obs variable

              final RxBool _profileInProgress = false.obs;
              

2. Show circularprogressindicator

                    SizedBox(
                        width: double.infinity,
                        child: Obx(() {
                          return _profileInProgress.value
                              ? const Center(
                            child: CircularProgressIndicator(),
                          )
                              : ElevatedButton(
                            onPressed: () {
                              updateProfile();
                            },
                            child: const Text('Update'),
                          );
                        }),
                      )
                      

Note Obx() . The obx() observe the variable _profileInProgress

3. show / hide loader

                        void updateProfile() async {
                            _profileInProgress.value = true;

                            .....
                            ......

                            _profileInProgress.value = false;

                        }