Creare un custom painter in Flutter

Attraverso la classe CustomPainter possiamo facilmente creare un custom painter in Flutter.

In questo articolo vediamo coome crearne uno.

Cominciamo proprio dalla nostra classe:

import 'package:flutter/material.dart';

class MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.amber
      ..strokeWidth = 5.0
      ..style = PaintingStyle.fill;

    Rect rect = const Rect.fromLTWH(50, 50, 100, 100);
    canvas.drawRect(rect, paint);

    Offset offset = Offset(size.width / 2, size.height / 2);
    canvas.drawCircle(offset, 50, paint);
  }

  @override
  bool shouldRepaint(CustomPainter delegate) {
    return false;
  }
}

Per usarlo;

import 'package:flutter/material.dart';

import 'custom_painter.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Test',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(
          seedColor: Colors.deepPurple,
        ),
        useMaterial3: true,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: const Text('Flutter Test'),
      ),
      body: Center(
        child: CustomPaint(
          painter: MyPainter(),
        ),
      ),
    );
  }
}

Enjoy!