title: flutter corner radius with transparent background
body: <p>Below is my code which I expect to render a round-corner container with a transparent background.  </p>
  
  <pre><code>return new Container(
                  //padding: const EdgeInsets.all(32.0),
                  height: 800.0,
                  //color: const Color(0xffDC1C17),
                  //color: const Color(0xffFFAB91),
                  decoration: new BoxDecoration(
                    color: Colors.green, //new Color.fromRGBO(255, 0, 0, 0.0),
                    borderRadius: new BorderRadius.only(
                      topLeft:  const  Radius.circular(40.0),
                      topRight: const  Radius.circular(40.0))
                  ),
                  child:  new Container(
                      decoration: new BoxDecoration(
                          color: Colors.blue,
                          borderRadius: new BorderRadius.only(
                              topLeft:  const  Radius.circular(40.0),
                              topRight: const  Radius.circular(40.0))
                      ),
                    child: new Center(
                      child: new Text("Hi modal sheet"),
                    )
  
                ),
  </code></pre>
  
  <p>However this is what it renders, it renders a white container (expected transparent) with a round corner radius. Any help? </p>
  
  <p><img src="https://i.stack.imgur.com/xTFCW.png" alt="screenshot"></p>