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import 'package:flutter/material.dart';
import 'dart:math' as math;
/// Your code should go into the DrawFractal class.
/// The fractal is drawn as an extension of the CustomPainter.
class DrawFractal extends CustomPainter {
var level = 10; // max level of fractal
// Constructor that initializes the level of the fractal
DrawFractal(value) {
level = value;
}
// Recursively draw the fractal
void fractal(Canvas canvas, int level) {
if (level >= this.level) {
return;
}
final paint = Paint()
..color = Colors.black
..strokeWidth = 1;
// Recursively draw the left branch
canvas.save();
canvas.rotate(math.pi / 6);
canvas.drawLine(Offset.zero, Offset(50 / level, 50 / level), paint);
canvas.translate(50 / level, 50 / level);
fractal(canvas, level + 1);
canvas.restore();
// As we go up the call stack, draw the right branch
canvas.rotate(-math.pi / 6);
canvas.drawLine(Offset.zero, Offset(50 / level, 50 / level), paint);
canvas.translate(50 / level, 50 / level);
fractal(canvas, level + 1);
}
/// Called when the canvas is (re)painted, perform the initial moving of the
/// fractal to the center and other actions here such as the initial call to fractal.
@override
void paint(Canvas canvas, Size size) {
fractal(canvas, 1);
}
/// Always repaint
@override
bool shouldRepaint(CustomPainter oldDelegate) {
return true;
}
}
// The code before here is to set up the flutter app and run it. You may not have to
// change this code.
/// Run the application
void main() => runApp(MyApp());
/// The application runs a streambuilder widget
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
// The title of my application
title: 'My flutter application',
home: StreamBuilderSetup(),
debugShowCheckedModeBanner: false,
);
}
}
/// Stream to generate numbers from 1 to 10
Stream<int> generateNumbers = (() async* {
await Future<void>.delayed(const Duration(seconds: 2));
for (int i = 1; i <= 10; i++) {
await Future<void>.delayed(const Duration(seconds: 1));
yield i;
}
})();
/// Setup a streambuild widget
class StreamBuilderSetup extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return _StreamBuilderSetupState();
}
}
/// The innards of the streambuilder widget
class _StreamBuilderSetupState extends State<StreamBuilderSetup> {
/// Boilerplate for initializing the state of the widget
@override
initState() {
super.initState();
}
/// Build the widget, it consists of a title and a SizedBox where the
/// drawing of the fractal (but could be anything takes place)
/// Most of this is boilerplate code.
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
// Title bar for the widget
title: const Text('Draw a Fractal in Flutter'),
),
// Box in which to draw the fractal
body: SizedBox(
width: double.infinity,
child: Center(
child: StreamBuilder<int>(
stream: generateNumbers,
initialData: 0,
builder: (
BuildContext context,
AsyncSnapshot<int> snapshot,
) {
if (snapshot.connectionState == ConnectionState.waiting) {
return Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.center,
children: [
const CircularProgressIndicator(),
Visibility(
visible: snapshot.hasData,
child: Text(
snapshot.data.toString(),
style:
const TextStyle(color: Colors.black, fontSize: 24),
),
),
],
);
} else if (snapshot.connectionState == ConnectionState.active ||
snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
return const Text('Error');
} else if (snapshot.hasData) {
return Center(
child: CustomPaint(
// Set up a canvas of size 500 by 5000
size: const Size(500, 500),
// Draw the fractal passing the level from the stream
painter: DrawFractal(snapshot.data)),
);
} else {
return const Text('Empty data');
}
} else {
return Text('State: ${snapshot.connectionState}');
}
},
),
),
),
);
}
}
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