title: Flutter email input formatter does not work
body: <p>I have a Flutter TextFormField for email with input formatter as below.</p>
  <pre class="lang-dart prettyprint-override"><code>var emailAddressFormatter = FilteringTextInputFormatter.allow(RegExp(
      r&quot;[a-zA-Z0-9.a-zA-Z0-9.!#$%&amp;'*+-/=?^_`{|}~]+@[a-zA-Z0-9]+\.[a-zA-Z]+&quot;));
  </code></pre>
  <p>The problem is, when trying to input any character in the field it does not allow. The regex looks fine to me. When the formatter is removed the field accepts any character with any format. What am I going wrong?</p>