Input validation flutter

input-validation.dart

// Simplified version with focusOut validation
Obx(
  () => Focus(
    onFocusChange: (hasFocus) {
      if (!hasFocus) {
        controller.stateTaxIdController.refresh();
        GetUtils.isCnpj(stateTaxIdMask.getUnmaskedText());
      }
    },
    child: TextFormFieldOnPrimary(
      controller: controller.stateTaxIdController.value,
      keyboardType: TextInputType.number,
      mask: [stateTaxIdMask],
      hintText: '87.880.524/0001-00',
                        //
                        // onChanged: (value) => controller.verifyCnpjIsValid(stateTaxIdMask.getUnmaskedText()),
      errorText: GetUtils.isCnpj(stateTaxIdMask.getUnmaskedText()) || controller.stateTaxIdController.value.text.length == 0
      ? null
      : AppText.stateTaxIdInvalid,
      validator: (value) {
        if (GetUtils.isCnpj(value)) return null;
        return 'CNPJ inválido';
      },
    ),
  ),
)

// TextFormField
Obx(
  () => TextFormFieldOnPrimary(
    controller: controller.stateTaxIdController,
    keyboardType: TextInputType.number,
    mask: [stateTaxIdMask],
    hintText: '87.880.524/0001-00',
                      //
    onChanged: (value) => controller.verifyCnpj(stateTaxIdMask.getUnmaskedText()),
    errorText: controller.isCnpjValid.value ? null : AppText.cnpjInvalid,
    validator: (value) {
      if (GetUtils.isCnpj(value)) {
        return null;
      }
      return 'CNPJ inválido';
    },
  )
)

// Submit button 
ButtonBase(
  text: "próximo",
  onPressed: () {
    if (_formKey.currentState.validate()) {
      controller.pageController.nextPage(duration: Duration(milliseconds: 200), curve: Curves.fastOutSlowIn);
    } else {
      ShowSnackBar.error("Corrigir os campos em destaque");
    }
  },
  icon: Icons.arrow_forward,
)
 
// Controller
class SignupOperatorController extends GetxController {
  final CompanyRepository companyRepository;
  SignupOperatorController({@required this.companyRepository}) : assert(companyRepository != null);
  static SignupOperatorController get to => Get.find();

  // Controllers
  final TextEditingController stateTaxIdController = TextEditingController();

  // Getters
  String get stateTaxId => stateTaxIdController.text;

  // Verications
  final isCnpjValid = true.obs; // start valid
  verifyCnpj(String value) {
    stateTaxId == "" ? isCnpjValid.value = true : isCnpjValid.value = GetUtils.isCnpj(value);
  }

  @override
  void onInit() async {
    print("[SignupOperatorController] - onInit");
    pageController = new PageController();
  }

  @override
  Future<void> onClose() async {
    print("[SignupOperatorController] - onClose");
    clear();
    stateTaxIdController?.dispose();
    super.onClose();
  }

  void clear() {
    stateTaxIdController.clear();
  }

}