title: Change value of text input in flutter
body: <p>I do the following to change the value of the input field. Regarding documentation this should work but it don't. Purpose is to open a google location search if location input is tapped and write the result value back to the text field. The following code is a simple version to show my problem:</p>
  
  <pre><code>            TextFormField(
               key: locationKey,
                  decoration:
                  InputDecoration(labelText: 'Location'),
               // onTap: openLocationSearch,
                onTap: () {
                  locationKey.currentState.didChange('test');
               },
            ),
  </code></pre>