title: how to distribute space between multiple items
body: <p>I am trying to add an image that covers the <strong>top 20%</strong> of the screen and the other <strong>80%</strong> should be a grid of cards. The image needs to be in the body and <strong>not on the Appbar</strong>. I made the grid of cards, and then I tried to put the image and the grid in a column. The implementation is the following.</p>
  
  <pre><code>  @override
    Widget build(BuildContext context) {
      return MaterialApp(
        home: Scaffold(
          primary: true,
          appBar: AppBar(
          elevation: 4.0,
          backgroundColor: Color(0xfff8f8f8),
          title: Center(child: titleLogo,),
          ),
    //------------ PROBLEM BELOW ----------------
          body: new Column(
            children: &lt;Widget&gt;[
              titleLogo,   //Image object
              TheGridView().build()  //Returns a GridView object
              ],
        ),
    ),
  );
  </code></pre>
  
  <p>}</p>
  
  <p>I am getting the following error</p>
  
  <pre><code>I/flutter (21751): The following assertion was thrown during performResize():
  I/flutter (21751): Vertical viewport was given unbounded height.
  I/flutter (21751): Viewports expand in the scrolling direction to fill their container.In this case, a vertical
  I/flutter (21751): viewport was given an unlimited amount of vertical space in which to expand. This situation
  I/flutter (21751): typically happens when a scrollable widget is nested inside another scrollable widget.
  I/flutter (21751): If this widget is always nested in a scrollable widget there is no need to use a viewport because
  I/flutter (21751): there will always be enough vertical space for the children. In this case, consider using a Column
  I/flutter (21751): instead. Otherwise, consider using the "shrinkWrap" property (or a ShrinkWrappingViewport) to size
  I/flutter (21751): the height of the viewport to the sum of the heights of its children.
  </code></pre>
  
  <p>Any suggestion is highly appreciated. Thank you in advance.</p>