title: Updating a text widget using onchanged
body: <p>I am trying to update a text widget as the user types, its working but i don't see the input as I type</p>
  <pre><code>         TextFormField(
              autofocus: true,
              controller: amountController,
              keyboardType: TextInputType.number,
              cursorColor: Colors.amber,
              decoration: InputDecoration(
                  hintText: &quot;Enter Amount&quot;,
                  prefixIcon: Material(
                    elevation: 0,
                    borderRadius: BorderRadius.all(Radius.circular(30)),
                    child: Icon(
                      Icons.phone_outlined,
                      size: 15,
                      color: Color(0xff020529),
                    ),
                  ),
                  border: InputBorder.none,
                  contentPadding:
                      EdgeInsets.symmetric(horizontal: 25, vertical: 13)),
              onChanged: (value) {
                add(value);
              },
            ),
  </code></pre>
  <p>this is the widget</p>
  <pre><code>       Text( x.toString(),
        style: TextStyle(fontWeight: FontWeight.bold),
        ),
  </code></pre>
  <p>This is my method</p>
  <pre><code>  add(String value) {
     var ans = 36 * double.parse(value);
    print('ddd');
    setState(() {
     x = ans;
    });
  </code></pre>
  <p><a href="https://i.stack.imgur.com/eyFCE.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eyFCE.gif" alt="enter image description here" /></a></p>