title: SingleChildScrollView height to max height with image background in flutter
body: <p>In the Login screen, there is a background image and all stuff will be scrollable but <code>SingleChildScrollView</code> is  not showing <code>macth_parent</code> height. My aim is to design like <a href="https://i.stack.imgur.com/NYupT.png" rel="noreferrer">here</a></p>
  
  <pre><code> class MyLoginOne extends StatelessWidget {
        @override
        Widget build(BuildContext context) {
          return new Scaffold(
           body: new Container(
             decoration: new BoxDecoration(
                 image: new DecorationImage(
                     fit: BoxFit.cover,
                     image:new NetworkImage('https://i.pinimg.com/originals/c2/47/e9/c247e913a0214313045a8a5c39f8522b.jpg')
                 )
             ),
             child: new BackdropFilter(
               filter:new ImageFilter.blur(sigmaX: 1.1,sigmaY:1.1),
               child: new Container(
                 decoration: new BoxDecoration(color: Colors.black45.withOpacity(0.5)),
                 child: new SingleChildScrollView(
                   child: new Container(
                     child: new Column(
                   children: &lt;Widget&gt;[
                   new Container(
                       height: 200.0,
                       child: new Stack(
                         children: &lt;Widget&gt;[
                           new Align(
                               alignment: AlignmentDirectional.center,
                               child:new Container(
                                 height: 120.0,
                                 width: 120.0,
                                 decoration: new BoxDecoration(
                                     shape: BoxShape.circle,
                                     color: Colors.white30
                                 ),
                               )
                           ),
                           new Align(
                             alignment: AlignmentDirectional.center,
                             child: new Container(
                               child: new Text("Farha",style: new TextStyle(
                                   color: Colors.white,
                                   fontSize: 14.0,
                                   fontFamily: "WorkSansLight"
                               ),),
                         ),),],))],),),)),), ));}}
  </code></pre>
  
  <p>my circle container height is about 200.0 but <code>SingleChildScrollView</code> is not showing full height.</p>
  
  <p><a href="https://i.stack.imgur.com/LRVkr.png" rel="noreferrer"><img src="https://i.stack.imgur.com/LRVkr.png" alt="enter image description here"></a></p>