如何根据另一个的值验证表单字段？

Question

我有2个表单域，我想验证第二个表单域以匹配第一个表单域的密码，我尝试了但没有成功..谢谢回答。

更新：我已经具有提交按钮及其功能，我想要第二个字段中的Validator来验证第一个字段文本以匹配第二个字段。

            new TextFormField(
          controller: _registerPassController,
          decoration: new InputDecoration(labelText: 'Password'),
          obscureText: true,
          validator: (value) =>
              value.isEmpty ? 'Password can\'t be empty' : null,
          onSaved: (value) => _password = value,
        ),
      ],
    ),
    new Stack(
      alignment: const Alignment(1.0, 1.0),
      children: <Widget>[
        new TextFormField(
          controller: _registerPassController2,
          decoration: new InputDecoration(labelText: 'Retype Password'),
          obscureText: true,
          validator: (value) {
            if (value.isEmpty) {
              return 'Please enter some text';
            }
          },),

Answer 1

我终于找到了答案，实际上它是如此简单。

        new TextFormField(
          controller: _registerPassController2,
          decoration: new InputDecoration(labelText: 'Retype Password'),
          obscureText: true,
          validator: (value) {
            if (value != _registerPassController.text) {
              return 'Password is not matching';
            }
          },
        ),

Answer 2

由于您使用的是formfield，因此使用键访问其他字段的值将是适当的。您可以这样声明全局密钥

var passKey = GlobalKey<FormFieldState>();

然后将其传递到密码字段以在验证过程中检索其值。

TextFormField(
  key: passKey,
  obscureText: true,
  decoration: InputDecoration(
      labelText: "Password"
  ),
  validator: (password){
    var result = password.length < 4 ? "Password should have at least 4 characters" : null;
    return result;
  },
);

然后，您可以像这样在确认验证器中使用密码

TextFormField(
  obscureText: true,
  decoration: InputDecoration(
      labelText: "Confirm Password"
  ),
  validator: (confirmation){
    var password = passKey.currentState.value;
    return equals(confirmation, password) ? null : "Confirm Password should match password";
  },
);

Answer 3

我这样做的方法是验证提交按钮，然后显示一条消息。

  String _password;
  Widget _passwordField() {
    return new TextFormField(
        autocorrect: false,
        obscureText: true,
        decoration: InputDecoration(labelText: 'Password'),
        validator: (value) =>
          value.isEmpty ? "Password can't be empty" : null,
        onSaved: (val) => _password = val;
  }

  String _passwordConfirm;
  Widget _passwordConfirmField() {
    return new TextFormField(
        autocorrect: false,
        obscureText: true,
        decoration: InputDecoration(labelText: 'Retype Password'),
        validator: (value) =>
          value.isEmpty ? "Password can't be empty" : null,
        onSaved: (val) => _passwordConfirm = val;
  }

  final formKey = new GlobalKey<FormState>();
  Widget _buildForm() {
     return new Form(
      autovalidate: true, 
      key: formKey, 
      child: new Column(children: <Widget>[
         _passwordField(),
         _passwordConfirmField(),
         new RaisedButton(
            child: Text('Sign Up'),
            onPressed: () => submit()
         )
      ]

  }

void submit() {
   final form = formKey.currentState;

   if (form.validate()) {
      form.save();  //this will cause the onSaved method to get called

      //you will need to do some additional validation here like matching passwords
      if(_password != _passwordConfirm) {
         showDialog(....)
      } else {
         //complete
      }
   } 

}

注意：这是一个StatefulWidget