how to distribute space between multiple items - dart

Question

I am trying to add an image that covers the top 20% of the screen and the other 80% should be a grid of cards. The image needs to be in the body and not on the Appbar. 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.
#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: <Widget>[
titleLogo, //Image object
TheGridView().build() //Returns a GridView object
],
),
),
);
}
I am getting the following error
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.
Any suggestion is highly appreciated. Thank you in advance.

Answer 1

for distributing space between multiple items you should use the Expanded widget like this:
return new Column(
children: <Widget>[
new Expanded(
flex: 2,
child: new Container(
color: Colors.red,
),
),
new Expanded(
flex: 8,
child: new Container(//use your Gridview instead
color: Colors.green,
)
)
],
);