颤振步进器小部件 - 在各个步骤中验证字段

Question

我正在使用步进器小部件从用户那里收集信息并对其进行验证，我需要在每个步骤中调用 API，因此在每个继续按钮的步骤中验证每个字段...我正在使用表单状态和表单小部件但问题是它验证步进器中所有步骤中的整个字段......我如何仅验证步进器中的单个步骤？我浏览了 stepper.dart 中的 Stepper 和 State 类中的文档，但那里没有支持功能

下面是代码

class SubmitPayment extends StatefulWidget {


 SubmitPayment({Key key, this.identifier, this.amount, this.onResendPressed})
      : super(key: key);

  final String identifier;
  final String amount;
  final VoidCallback onResendPressed;

  @override
  State<StatefulWidget> createState() {
    return _SubmitPaymentState();
  }
}

class _SubmitPaymentState extends State<SubmitPayment> {
  final GlobalKey<FormState> _formKeyOtp = GlobalKey<FormState>();
  final FocusNode _otpFocusNode = FocusNode();
  final TextEditingController _otpController = TextEditingController();
  bool _isOTPRequired = false;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.only(top: 8.0),
      child: Form(
          key: _formKeyOtp,
          child: Column(children: <Widget>[
            Center(
                child: Padding(
                    padding:
                        EdgeInsets.symmetric(horizontal: 16.0, vertical: 5.0),
                    child: Text(
                      Translations.of(context).helpLabelOTP,
                      style: TextStyle(
                          color: Theme.of(context).primaryColor,
                          fontStyle: FontStyle.italic),
                    ))),
            CustomTextField(
              icon: Icons.vpn_key,
              focusNode: _otpFocusNode,
              hintText: Translations.of(context).otp,
              labelText: Translations.of(context).otp,
              controller: _otpController,
              keyboardType: TextInputType.number,
              hasError: _isOTPRequired,
              validator: (String t) => _validateOTP(t),
              maxLength: AppConstants.otpLength,
              obscureText: true,
            ),
            Center(
                child: ButtonBar(
              mainAxisSize: MainAxisSize.max,
              alignment: MainAxisAlignment.center,
              children: <Widget>[
                RaisedButton(
                  child: Text(Translations.of(context).resendOtpButton),
                  color: Colors.white,
                  textColor: Theme.of(context).primaryColor,
                  onPressed: widget.onResendPressed,
                ),
                RaisedButton(
                  child: Text(
                    Translations.of(context).payButton,
                  ),
                  onPressed: _doPullPayment,
                ),
              ],
            )),
          ])),
    );
  }

  String _validateOTP(String value) {
    if (value.isEmpty || value.length < AppConstants.otpLength) {
      setState(() => _isOTPRequired = true);
      return Translations.of(context).invalidOtp;
    }
    return "";
  }

  bool _validateOtpForm() {
    _formKeyOtp.currentState.save();
    return this._formKeyOtp.currentState.validate();
  }

  Future<void> _doPullPayment() async {
    setState(() {
      _isOTPRequired = false;
    });

    if (!_validateOtpForm()) return false;

    try {
      setState(() {
        _isOTPRequired = false;
      });
      showDialog(
        barrierDismissible: false,
        context: context,
        builder: (context) => AlertDialog(
              content: ListTile(
                leading: CircularProgressIndicator(),
                title: Text(Translations.of(context).processingPaymentDialog),
              ),
            ),
      );

      TransactionApi api =
          TransactionApi(httpDataSource, authenticator.sessionToken);
      String responseMessage = await api.doPullPayment(
          widget.identifier,
          widget.amount,
          _otpController.text,
          TransactionConstants.transactionCurrency);

      Navigator.of(context).pop();
      await showAlertDialog(
          context, Translations.of(context).pullPayment, '$responseMessage');
      Navigator.pop(context);
    } catch (exception) {
      await showAlertDialog(context, Translations.of(context).pullPayment,
          '${exception.message}');
      Navigator.of(context).pop();
    }
  }

Answer 1

为每个步骤使用单独的Form。使用GlobalKey<FormState> 的列表，您可以根据_currentStep 对其进行索引，然后在onStepContinue 中调用validate()：

List<GlobalKey<FormState>> _formKeys = [GlobalKey<FormState>(), GlobalKey<FormState>(), …];
…

Stepper(
  currentStep: _currentStep,
  onStepContinue: () {
    setState(() {
      if (_formKeys[_currentStep].currentState.validate()) {
        _currentStep++;
      }
    });
  },
  steps: 
  Step(
    child: Form(key: _formKeys[0], child: …),

显然，您需要检查最后一步和save，而不是最后的validate :)

Answer 2

所以我解决了这个问题：

问题是，如果我的逻辑有效，我将返回一个 *empty string ("") *，其中 validate 方法是 FormState 期望与 TextFormField 关联的每个验证器方法在验证通过时返回 null。

我改变了以下

 String _validateOTP(String value) {
    if (value.isEmpty || value.length < AppConstants.otpLength) {
      setState(() => _isOTPRequired = true);
      return Translations.of(context).invalidOtp;
    }
    return "";
  }

到

  String _validateOTP(String value) {
if (value.isEmpty || value.length < AppConstants.otpLength) {
  setState(() => _isOTPRequired = true);
  return Translations.of(context).invalidOtp;
}
return null;

}

然后一切正常。

详情请参考link "If there is an error with the information the user has provided, the validator function must return a String containing an error message. If there are no errors, the function should not return anything."