Flutter: Remove space between widgets - flutter

Question

By using CustomPainter i have created a half circle.Now i have this widget tree:
return Scaffold(
body: Center(
child: SingleChildScrollView(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Container(
// card view
height: 100,
alignment: Alignment.center,
margin: EdgeInsets.only(
top: 20.0, bottom: 0.0, left: 50.0, right: 50.0),
decoration: BoxDecoration(
boxShadow: ([
BoxShadow(
color: color_transparent_black,
spreadRadius: 5,
blurRadius: 3.0,
offset: Offset(2, 3),
),
]),
borderRadius: BorderRadius.circular(14.0),
),),
MyArc(diameter: 200),
This is MyArc:
class MyArc extends StatelessWidget {
final double diameter;
const MyArc({Key key, this.diameter = 200}) : super(key: key);
#override
Widget build(BuildContext context) {
return CustomPaint(
painter: MyPainter(),
size: Size(diameter, diameter),
);
}
}
// This is the Painter class
class MyPainter extends CustomPainter {
#override
void paint(Canvas canvas, Size size) {
Paint paint = Paint()..color = Colors.blue;
canvas.drawArc(
Rect.fromCenter(
center: Offset(size.height / 2, 0),
height: size.height,
width: size.width,
),
6.4,
2.9,
false,
paint,
);
}
#override
bool shouldRepaint(CustomPainter oldDelegate) => false;
}
But i got this problem:
I don't want any space between gray and blue shape!!!

Answer 1

I finally figured it out...
import 'dart:math' as math;
//...
class MyPainter extends CustomPainter {
#override
void paint(Canvas canvas, Size size) {
Paint blue = Paint()..color = Colors.blue;
canvas.translate(0, -size.height / 2);
canvas.drawArc(
Offset.zero & size,
-math.pi,
-math.pi,
false,
blue,
);
}
#override
bool shouldRepaint(CustomPainter oldDelegate) => false;
}
If you want to make your canvas fit nicely also you can make it rectangular like so...
CustomPaint(
painter: MyPainter(),
size: Size(diamieter, diameter / 2),
)
Then have you custom painter as...
class MyPainter extends CustomPainter {
#override
void paint(Canvas canvas, Size size) {
Paint blue = Paint()..color = Colors.blue;
Paint red = Paint()..color = Colors.red;
canvas.drawRect(Offset.zero & size, red);
canvas.translate(0, -size.height);
canvas.drawArc(
Offset.zero & Size(size.width, size.height * 2),
-math.pi,
-math.pi,
false,
blue,
);
}
#override
bool shouldRepaint(CustomPainter oldDelegate) => false;
}
It'll fit snug this way...

Answer 2

try changing the spreadRadius to 3.0
Its possible that it's creating a boundary greater than the container's Blur Radius boundary.
BoxShadow(
color: color_transparent_black,
spreadRadius: 5,
blurRadius: 3.0,
offset: Offset(2, 3),
),