How to draw widget on available height in flutter - flutter

Question

I have a widget that needs to draw on the remaining height where that widget needs to be drawn in between the top and bottom widget(Bottom widget drawn with bottom center attribute).
Ex:
Container() -- The First container almost take half screen
Container() -- The Second container draw on the bottom of the screen eg: Consider widget as Button
Container() -- The Third Container needs to be drawn in between two containers.

Answer 1

The Expanded widget would work for this scenario where we need to wrap middle widget with it.
Eg:
Expanded(
child: Container(
...
),
),

Answer 2

I know a better method using MediaQuery.of(), where you just put the percentage of the space available that a widget will cover:
final mediaQuery = MediaQuery.of(context);
const SizedBox(height: mediaQuery.size.heigh * [percentage of the screen]
But this way includes AppBar space too. So if you want to exclude it, you should do this:
Create appBar variable:
final PreferredSizeWidget appBar = AppBar(
title: const Text('Personal expensense'),
);
Subtract mediaQuery.size with appBar variable size:
final availableHeight = mediaQuery.size.height -
appBar.preferredSize.height -
mediaQuery.padding.top;
A full example:
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
final PreferredSizeWidget appBar = AppBar(
title: const Text('Personal expensense'),
);
final mediaQuery = MediaQuery.of(context);
final availableHeight = mediaQuery.size.height -
appBar.preferredSize.height -
mediaQuery.padding.top;
return Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: [
SizedBox(
height: availableHeight * 0.4,
child: Container(),
),
SizedBox(
height: availableHeight * 0.3,
child: Container(),
),
SizedBox(
height: availableHeight * 0.3,
child: Container(),
),
],
);
}
}
It happens to be really useful!

Answer 3

If you have something like a Column, you probably want to use the Expanded widget.
Try this code
Column(
children: [
Container(color: Colors.red, height: 100),
Expanded(
child: Container(color: Colors.yellow, height: 100),
),
Container(color: Colors.red, height: 100),
],
)
From the Expanded-class documentation:
A widget that expands a child of a Row, Column, or Flex so that the
child fills the available space.