title: Flutter: How to change the width of an AlertDialog?
body: <p>I wonder how to change the default width of an AlertDialog, I only succeeded to change the border radius :</p>
  
  <p>Here is my code :</p>
  
  <pre><code>showDialog(
         context: context,
         builder: (_) =&gt;
              new AlertDialog(
                 shape: RoundedRectangleBorder(
                     borderRadius: BorderRadius.all(Radius.circular(10.0))
                 ),
                 content: ProductPreviewScreen(),
              )
      );
  </code></pre>
  
  <p>Result expected :</p>
  
  <p><a href="https://i.stack.imgur.com/1fIJa.png" rel="noreferrer"><img src="https://i.stack.imgur.com/1fIJa.png" alt="enter image description here"></a>
  Any idea?</p>