title: Email validation not working in flutter display message even if email address is correct
body: <p>In this code, the empty-email validation works but email-type validation does not work. Email-type validation still displays the "Invalid Email" message if a valid email address is inserted.    </p>
  
  <pre><code>new TextFormField(
        decoration: new InputDecoration(
          labelText: 'Email'
        ),
        validator: (value){
          if (value.isEmpty) {
            return 'Email is required';
          }
          if(!value.contains(r'^(([^&lt;&gt;()[\]\\.,;:\s@\"]+(\.[^&lt;&gt;()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$')){
            return 'Invalid Email';
          }
          return null;
        },
      )
  </code></pre>
  
  <p>The line that is potentially erroneous is: </p>
  
  <pre><code>if(!value.contains(r'^(([^&lt;&gt;()[\]\\.,;:\s@\"]+(\.[^&lt;&gt;()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$'))
  </code></pre>