main.dart

            child: TextFormField(
              controller: nameController,
              decoration: InputDecoration(
                labelText: "Enter Pet Name",
                enabledBorder: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(10.0),
                ),
              ),
              // The validator receives the text that the user has entered.
              validator: (value) {
                if (value.isEmpty) {
                  return 'Enter Pet Name';
                }
                return null;
              },
            ),