Show Snackbar above to showModalBottomSheet Flutter

我已经展示了MoalBottomSheet来获取动态口令代码，如果用户输入错误的代码，我想要显示Snackbar.所以，我用了这个方法，

showModalBottomSheet(
        isScrollControlled: true,
        isDismissible: false,
        context: context,
        builder: (context) {
          return SafeArea(
            child: Stack(
              alignment: Alignment.topCenter,
              clipBehavior: Clip.none,
              children: [
                Column(
                  children: [
                    Container(
                      padding: const EdgeInsets.symmetric(
                          horizontal: 30, vertical: 0),
                      child: Column(children: [
                        Padding(
                          padding:
                              const EdgeInsets.symmetric(horizontal: 50),
                          child: TextField(
                            controller: codeController,
                            keyboardType: TextInputType.number,
                          ),
                        ),
                        const SizedBox(
                          height: 5,
                        ),
                        Padding(
                          padding:
                              const EdgeInsets.symmetric(horizontal: 50),
                          child: CustomButton(
                              onTap: () async {
                                if (codeController.text.length == 6) {
                                  try {
                                    PhoneAuthCredential credential =
                                        PhoneAuthProvider.credential(
                                            verificationId: verificationId,
                                            smsCode:
                                                codeController.text.trim());
                                    await _auth
                                        .signInWithCredential(credential);
                                    Navigator.of(context)
                                        .pushNamedAndRemoveUntil(
                                            '/home',
                                            (Route<dynamic> route) =>
                                                false);
                                  } catch (e) {
                                  // ---------------------------------------------- 
                                  //this snackbar 
                                     showSnackBar(
                                           context,
                                           "Invalid verification code",
                                          "Please enter correct verification code");
                                    }
                                  }
                              },
                              text: "Continue",
                              height: 50),
                        )
                      ]),
                    )
                  ],
                )
              ],
            ),
          );
        });
  

显示在showMoalBottomSheet下面的Snackbar，所以我想显示上面的Snackbar以显示ModalBottomSheet，而不隐藏showMoalBottomSheet.