Flutter - Drawing a rectangle in bottom - dart

Question

I'm trying to draw a rectangle at the bottom only the Rect object Rect.fromLTRB is not drawing.
I do not know if I'm interpreting the Rect object in the wrong way or I'm writing the drawRect object erroneously.
Could you help me draw a rectangle in the bottom?
import 'package:flutter/material.dart';
void main() {
runApp(new MaterialApp(home: new HomePage()));
}
class HomePage extends StatefulWidget {
#override
HomePageState createState() => new HomePageState();
}
class HomePageState extends State<HomePage> {
#override
Widget build(BuildContext context) {
return new Scaffold(
body: new Stack(
children: <Widget>[
new Positioned(
bottom: 0.0,
left: 0.0,
right: 0.0,
top: 0.0,
child: new CustomPaint(
painter: new Sky(),
)
),
]
)
);
}
}
class Sky extends CustomPainter {
#override
void paint(Canvas canvas, Size size) {
canvas.drawRect(
new Rect.fromLTRB(
0.0, 100.0, 0.0, 0.0
),
new Paint()..color = new Color(0xFF0099FF),
);
}
#override
bool shouldRepaint(Sky oldDelegate) {
return false;
}
}

Answer 1

Your left and right is the same (0.0) so it draws an empty rect. Also the coordinates start on top, so bottom should be > top; Try this
new Rect.fromLTRB(
0.0, 0.0, 20.0, 100.0
)

Answer 2

Follows the code in which the rectangle is in the bottom of screen:
import 'package:flutter/material.dart';
import 'dart:ui' as ui;
void main() {
runApp(new MaterialApp(home: new HomePage()));
}
class HomePage extends StatefulWidget {
#override
HomePageState createState() => new HomePageState();
}
class HomePageState extends State<HomePage> {
#override
Widget build(BuildContext context) {
final ui.Size logicalSize = MediaQuery.of(context).size;
final double _width = logicalSize.width;
final double _height = logicalSize.height;
double _rectHeight = 50.0;
return new Scaffold(
body: new Stack(
children: <Widget>[
new Positioned(
bottom: 0.0,
left: 0.0,
top: _height - _rectHeight,
right: 0.0,
child: new CustomPaint(
painter: new Sky(_width, _rectHeight),
child: new Text('$_width'),
)
),
]
)
);
}
}
class Sky extends CustomPainter {
final double _width;
final double _rectHeight;
Sky(this._width, this._rectHeight);
#override
void paint(Canvas canvas, Size size) {
canvas.drawRect(
new Rect.fromLTRB(
0.0, 0.0, this._width, _rectHeight
),
new Paint()..color = new Color(0xFF0099FF),
);
}
#override
bool shouldRepaint(Sky oldDelegate) {
return false;
}
}