title: Flutter TextInputType.number is not forcing a number only keyboard
body: <p>I don't understand what I'm missing here. I put TextInputType to number, and can still type any letter, special character and even an emoji. I have also tried making the child a TextInputType.numberWithOptions() widget, and it opens the same keyboard. Is this just a bug on my phone? P20 Pro</p>
  
  <pre><code>      Row(
            children: &lt;Widget&gt;[
              Text('TextInputType.number:'),
              Flexible(
                  child: TextField(
                maxLength: 3,
                keyboardType: TextInputType.number,
              )),
            ],
          )
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/BwSkO.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/BwSkO.jpg" alt="Should be numbers only"></a></p>