title: Full width DropdownButton with adjust dropdown arrow icon in Flutter
body: <p>I needed to add DropdownButton with full width with adjust dropdown arrow icon in Flutter as well. But with many tried it in many ways but it doesn't expand its width full.</p>
  
  <p>This is my code for <code>DropdownButton</code>:</p>
  
  <pre><code>new Expanded(
      child: new Column(
      children: &lt;Widget&gt;[
          new DropdownButton(
              items: [
                  new DropdownMenuItem(child: new Text("Abc")),
                  new DropdownMenuItem(child: new Text("Xyz")),
              ],
              hint: new Text("Select City"),
              onChanged: null
            )
         ]
      ),
      flex: 1,
  )
  </code></pre>