title: How to reset error message in TextFormField?
body: <p>I know this is a simple question but i did not find how to do this. How can i reset error message in TextFormField when the user input something in the field. Something like onchange listener. I notice onChanged is available in TextField but not TextFormField. How can i do this?</p>
  
  <pre><code>final _email = Container(
    child: TextFormField(
      decoration: InputDecoration(labelText: email),
      keyboardType: TextInputType.emailAddress,
      controller: emailController,
      validator: _validateEmail,
      onSaved: (input) =&gt; _stringEmail = input.toLowerCase().trim(),
    ),
  );
  </code></pre>
  
  <p>UPDATE: I am using controller to add listener for user input. But i just want to reset the error message instead of validating the form again. Is this possible? How can i do this?</p>
  
  <pre><code>  _resetEmailErrorMessage() {
      print("Second text field: ${emailController.text}");
      //replace clear to something that can reset the validation error message
      emailController.clear();
    }
  
    @override
    void initState() {
      super.initState();
  
      //start listening to changes
      emailController.addListener(_resetEmailErrorMessage);
    }
  </code></pre>