flutter - TextFormField 不显示验证错误

Question

如果在 TextFormField 中验证发现错误消息，我该如何显示？

我正在使用 Stepper 类来处理用户注册，当尝试使用 setState 实现基本验证时，当前正在验证的文本字段中没有显示错误消息

这是我的代码:

...
class _RegisterState extends State<RegisterPage> {
  static TextEditingController _inputController = TextEditingController();
  static bool _validate = false;
  static String _errorMessage;
  static int _currentStep = 0;
  static List<Step> _steps = [
    Step(
      // Title of the Step
      title: Text("Phone Number"),
      subtitle:
          Text('We need your 11 digit phone number to verify your identity!'),
      content: TextFormField(
        controller: _inputController,
        decoration: InputDecoration(
          icon: Icon(Icons.phone),
          labelText: '01XXXXXXXXX',
          errorText: _validate ? _errorMessage : null,
        ),
        maxLength: 11,
        keyboardType: TextInputType.number,
      ),
      state: _validate ? StepState.error : StepState.editing,
      isActive: true,
    ),
// Other steps ...
  ];

  @override
  Widget build(BuildContext context) {
    return CustomScaffold(
      title: 'Signup',
      body: Stepper(
        controlsBuilder: (BuildContext context,
            {VoidCallback onStepContinue, VoidCallback onStepCancel}) {
          return Row(
            mainAxisAlignment: MainAxisAlignment.start,
            children: <Widget>[
              RaisedButton(
                onPressed: onStepContinue,
                color: Theme.of(context).accentColor,
                child: const Text('Continue'),
              ),
              FlatButton(
                onPressed: onStepCancel,
                child: const Text('Cancel'),
              ),
            ],
          );
        },
        currentStep: _currentStep,
        type: StepperType.vertical,
        steps: _steps,
        // Actions
        onStepTapped: (step) {
          setState(() {
            _currentStep = step;
          });
        },
        onStepCancel: () {
          setState(() {
            if (_currentStep > 0) {
              _currentStep = _currentStep - 1;
            } else {
              App.router.pop(context);
            }
          });
        },
        onStepContinue: () => _validator(),
      ),
    );
  }

  void _validator() {
    if (_currentStep == 0) {
      // Validate number
      if (_inputController.text.length != 11) {
        setState(() {
          _validate = true;
          _errorMessage = "Phone number must be 11 digits";
        });
      } else if (!_matchInt()) {
        setState(() {
          _validate = true;
          _errorMessage = "Phone number must be correct";
        });
      }
    }
  }

  _matchInt() {
    RegExp re = RegExp(
      r'(\d{11})',
      multiLine: false,
    );
    return re.hasMatch(_inputController.text);
  }

  void _continue(int currentStep) {
    setState(() {
      if (_currentStep < _steps.length - 1) {
        _currentStep = _currentStep + 1;
      } else {
        // TODO: Validate data and register a new user
        return null;
      }
    });
  }
}

按 Continue 按钮没有显示任何错误!

Answer 1

与其在构建方法之外创建 Step，不如在构建方法内部创建它。

确保您在 StateFullWidget 中构建您的 TextField 小部件

您还可以使用 onChange 检查您的文本

                  TextField(
                    controller: textEditingController,
                    onChanged: (String string){
                      print(string);
                      print(_validate);
                      if (string.length < 3) {
                        setState(() {
                          _validate = true;
                        });
                      }else {
                        setState(() {
                          _validate = false;
                        });
                      }
                    },
                    keyboardType: TextInputType.number,
                    decoration: new InputDecoration(hintText: 'Enter the number',
                        errorText: _validate ? 'here' : 'change'),
                  )