title: Flutter - CupertinoPicker in an alert dialog
body: <p>I am stuck right now with the little app that I am trying to create.</p>
  <p>The user when he will tap on an icon is supposed to get an alert dialog with 2 buttons (OK and Cancel), and in the body of the alert box, a Cupertino Picker. Below you will find the code. I am getting this error message.</p>
  <blockquote>
  <p>Failed assertion: line 85 pos 15: 'children != null': is not true.</p>
  </blockquote>
  <pre><code>    class Engage extends StatefulWidget {
    Engage ({Key key}) : super(key:key);
    @override
    _EngageState createState() =&gt; _EngageState();
  }
  
  class _MyEngageState extends State&lt;MyEngage&gt; {
    @override
    Widget build(BuildContext context) {
      return Container(
        padding: const EdgeInsets.all(10.0),
        decoration: BoxDecoration(
            border: Border.all(color: Colors.grey[350])),
        child: Column(
         children: [
           Padding(
             padding: const EdgeInsets.all(3.0),
             child: Container(
                // margin: const EdgeInsets.all(30.0),
                 padding: const EdgeInsets.all(10.0),
                 decoration: BoxDecoration(
                     border: Border.all(color: Colors.grey[350])
                 ),
                child : Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    GestureDetector(
                      child: Column(
                        children: [
                          IconButton(
                           splashColor: Colors.lightGreenAccent,
                            icon : Image.asset('assets/icons/icon1',
                            height: iconHeighEngage,),
                             onPressed:(){
                                showDialog(
                                context: context,
                                builder: (BuildContext context) {
                                return AlertDialog(
                                   title: Text('TEST'),
                                     content: Container(
                                height: 350,
                                       child: Column(
                                children: &lt;Widget&gt;[
                                         CupertinoPicker(),
                                       FlatButton(
                                        child: Text(&quot;OK&quot;),
                                onPressed: () {
                                Navigator.pop(context);
                                },
                                )
                                ],
                                ),
                                ));
                                });
                                },
                                ),
                             Text('TEST')],
                      ),
                      ),
  </code></pre>