【 Flutter 】Flutter を 基礎 から 学習 ( ウィジェット編 ) part74 Painting and effects

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_app/mypainter.dart';

void main() {
  runApp(new MaterialApp(home: new MyApp()));
}

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _State();
  }
}

class _State extends State<MyApp> {
  int _index = 0;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      appBar: AppBar(
        title: Text('テスト中です。'),
      ),
      body: CustomPaint(
        painter: MyPainter(),
      ),
    ));
  }
}

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

class MyPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    // カスケード記法でしたかね！
    final paint = Paint()..color = Colors.blue;
    canvas.drawRect(Rect.fromLTWH(0, 0, 50, 50), paint);
    paint.color = Colors.grey;
    paint.strokeWidth = 5;
    canvas.drawLine(Offset(140, 10), Offset(140, 60), paint);
    paint.color = Colors.red;
    canvas.drawCircle(Offset(100, 35), 25, paint);
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return true;
  }
}