Snackbar is not showing up and pushes user to the next page - flutter

Question

I added a snackbar for the user which shows up when all fields aren't filled or when the sign up form is partially filled. Instead of displaying the snackbar, it takes the user to the next screen. I am wondering how it is managing to do that and getting past the if/else statement blocks. I'd appreciate if anyone could give tips or showcase what I am doing wrong.
final emailRegistered = signupEmailController.text.trim();
final usernameRegistered = signupNameController.text.trim();
final passwordRegistered = signupPasswordController.text.trim();
final retypePassRegistered = signupConfirmPasswordController.text.trim();
// final user = ParseUser.createUser()
// If form is valid then move forward
if (_formKey.currentState!.validate()) {
final user = ParseUser.createUser(usernameRegistered, passwordRegistered, emailRegistered);
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => const InterestsPage()),
);
// ScaffoldMessenger.of(context).showSnackBar(
// const SnackBar(content: Text('Processing Data')),);
} else {
// ScaffoldMessenger.of(context).showSnackBar(
// const SnackBar(content: Text('Field is unfilled', style: TextStyle(fontSize: 12),)),);
if (usernameRegistered.isEmpty == true &&
passwordRegistered.isEmpty == true &&
retypePassRegistered.isEmpty == true && emailRegistered.isEmpty == true) {
final materialBanner = MaterialBanner(
/// need to set following properties for best effect of awesome_snackbar_content
elevation: 0,
backgroundColor: Colors.transparent,
forceActionsBelow: true,
content: AwesomeSnackbarContent(
title: 'All fields are empty',
message:
'This is an example error message that will be shown in the body of materialBanner!',
/// change contentType to ContentType.success, ContentType.warning or ContentType.help for variants
contentType: ContentType.success,
// to configure for material banner
inMaterialBanner: true,
),
actions: const [SizedBox.shrink()],
);
ScaffoldMessenger.of(context)
..hideCurrentMaterialBanner()
..showMaterialBanner(materialBanner);
} else if (emailRegistered.isEmpty == true) {
final materialBanner = MaterialBanner(
/// need to set following properties for best effect of awesome_snackbar_content
elevation: 0,
backgroundColor: Colors.transparent,
forceActionsBelow: true,
content: AwesomeSnackbarContent(
title: 'Email is empty!',
message:
'This is an example error message that will be shown in the body of materialBanner!',
/// change contentType to ContentType.success, ContentType.warning or ContentType.help for variants
contentType: ContentType.success,
// to configure for material banner
inMaterialBanner: true,
),
actions: const [SizedBox.shrink()],
);
ScaffoldMessenger.of(context)
..hideCurrentMaterialBanner()
..showMaterialBanner(materialBanner);
} else if (passwordRegistered.isEmpty == true) {
const SnackBar(content: Text('Password is unfilled.'));
} else if (passwordRegistered != retypePassRegistered) {
const SnackBar(content: Text('Passwords do not match.'));
} else if (usernameRegistered.isEmpty == true) {
const SnackBar(content: Text('Username is unfilled'));
}
}

Answer 1

you forgot to call ScaffoldMessenger.of(context).showSnackBar method to create one snack bar variable then after showing snack bar.
For eg:
onPressed:(){
var snackBar;
if(){
//your other stuff
} else if (passwordRegistered.isEmpty == true) {
snackBar = SnackBar(content: Text('Password is unfilled.'));
} else if (passwordRegistered != retypePassRegistered) {
snackBar = SnackBar(content: Text('Passwords do not match.'));
} else if (usernameRegistered.isEmpty == true) {
snackBar = SnackBar(content: Text('Username is unfilled'));
}
ScaffoldMessenger.of(context).showSnackBar(snackBar);//important point
}//completion on pressed