title: How to display in TextField only double value
body: <p>I've got Text field which updateds a value variable to double format in onChange... I want the TextField only display the updated the value variable.. I don't want the textfield to display any string value or values which are not in double format by pressing wrong keyboard key. Even with numeric keyboard with decimal enabled we can press decimal key multiple times which I don't want to display in the TextField.</p>
  
  <pre><code>TextFormField(
          decoration: InputDecoration(labelText: 'Value'),
          onChanged: (s) {
            if (double.tryParse(s) != null)
              setState(() {
                value = double.parse(s);
              });
          },
        )
  </code></pre>
  
  <p>How can I display only parsed value in TextField? </p>