title: Icon not showing up in PopupMenuButton in Flutter
body: <p>I'm trying to create a PopupMenu in Flutter that comes down below the icon. However, the icon is not showing up. I am using the code suggested in this issue: <a href="https://stackoverflow.com/questions/54712976/is-it-possible-to-use-a-dropdownbutton-within-an-iconbutton-in-flutter">Is it possible to use a DropDownButton within an IconButton in Flutter?</a> but trying to adapt it to my widget tree.</p>
  
  <p>I have attached a sample of the code I tried.</p>
  
  <pre><code>@override
    Widget build(BuildContext context) {
      return new Container(
        height: MediaQuery.of(context).size.height,
        child: SingleChildScrollView(
          child: new Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisSize: MainAxisSize.max,
            children: &lt;Widget&gt;[
              new Container(
                height: 220.0,
                width: MediaQuery.of(context).size.width,
                child: new GestureDetector(
                  onTap: () {
                    FocusScope.of(context).requestFocus(new FocusNode());
                  },
                  child: Column(
                    children: &lt;Widget&gt;[
                      SizedBox(height: 40.0),
                      Row(
                        children: &lt;Widget&gt;[
                          Expanded(
                            child: Stack(
                              children: [
                                Center(
                                  child: Text(
                                    'Profile',
                                    textAlign: TextAlign.center,
                                    style: TextStyle(
                                      fontFamily: 'Lato',
                                      color: Colors.white,
                                      fontSize: 50.0,
                                      fontWeight: FontWeight.w700,
                                    ),
                                  ),
                                ),
                                Positioned(
                                  right: 8,
                                  child: Row(
                                    crossAxisAlignment: CrossAxisAlignment.center,
                                    mainAxisAlignment: MainAxisAlignment.center,
                                    children: &lt;Widget&gt;[
                                      Padding(padding: EdgeInsets.only(top: 400)),
                                      PopupMenuButton&lt;String&gt;(
                                        icon: Icon(
                                          Icons.settings,
                                          color: Colors.white,
                                          size: 30.0,
                                        ),
                                        onSelected: choiceAction,
                                        itemBuilder: (BuildContext context) {
                                          return Constants.choices.map((String choice) {
                                            return PopupMenuItem&lt;String&gt;(
                                              value: choice,
                                              child: Text(choice),
                                            );
                                          }).toList();
                                        },
                                      ),
                                    ],
                                  ),
                                ),
                              ],
                            ),
                          ),
                        ],
                      ),
  </code></pre>