title: how to set CupertinoSegmentedControl height?
body: <p>I am trying to use <code>CupertinoSegmentedControl</code> from the flutter <em>Cupertino library</em> in the <code>AppBar</code> using the bottom attribute to achieve the following design (height = 32)</p>
  
  <p><a href="https://i.imgur.com/CGQfXlw.jpg" rel="nofollow noreferrer"><img src="https://i.imgur.com/CGQfXlw.jpg" alt="cupertino segmented control"></a></p>
  
  <p>so I tried the following :</p>
  
  <pre><code>@override
      Widget build(BuildContext context) {
          return Scaffold(
                  appBar: AppBar(
                      elevation: 2,
                      backgroundColor: Colors.white,
                      centerTitle: true,
                      title: Text(this.widget.title, style: TextStyle(color: Colors.black)),
                      bottom: PreferredSize(
          child: Padding(
            padding: const  EdgeInsets.only(top: 8, bottom: 12),
            child: Row(
              children: &lt;Widget&gt;[
                SizedBox(width: 24),
                Expanded(
                  child: CupertinoSegmentedControl(
                    children: this.widget.tabs,
                    groupValue: this._selectedTab,
                    onValueChanged: (value) {
                      this.setState(() =&gt; this._selectedTab = value);
                      this._tabController.animateTo(value);
                    }
                  ),
                ),
                SizedBox(width: 24)
              ],
            ),
          ),
          preferredSize: Size(double.infinity, 48)
        )
                  ),
                  body: new TabBarView(
                      controller: this._tabController,
                      children: this.widget.views,
                  ));
      } 
  </code></pre>