iroute/assets/draw/p03/s04.dart

import 'dart:math';
import 'dart:typed_data';
import 'dart:ui';

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

/// create by 张风捷特烈 on 2020-03-19
/// contact me by email 1981462002@qq.com
/// 说明: 纸

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

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: CustomPaint( // 使用CustomPaint
        painter: PaperPainter(),
      ),
    );
  }
}

class PaperPainter extends CustomPainter {
  late Paint _paint;

  late Paint _gridPint;
  final double step = 20;
  final double strokeWidth = 0.5;
  final Color color = Colors.blue;

  PaperPainter() {
    _paint = Paint()
      ..style = PaintingStyle.fill
      ..strokeWidth = strokeWidth
      ..color = color;
    _gridPint = Paint()
      ..style = PaintingStyle.stroke
      ..strokeWidth = strokeWidth
      ..color = Colors.grey;
  }

  @override
  void paint(Canvas canvas, Size size) {
    canvas.translate(size.width / 2, size.height / 2);
    _drawGrid(canvas, size);
    _drawAxis(canvas,size);

    _drawPointsWithPoints(canvas);
    // _drawPointsWithLines(canvas);
    _drawPointLineWithPolygon(canvas);
    _drawRawPoints(canvas);
  }

  final List<Offset> points = [
    Offset(-120, -20),
    Offset(-80, -80),
    Offset(-40, -40),
    Offset(0, -100),
    Offset(40, -140),
    Offset(80, -160),
    Offset(120, -100),
  ];

  void _drawPointsWithPoints(Canvas canvas) {
    _paint
      ..color = Colors.red
      ..style = PaintingStyle.stroke..strokeWidth=10
      ..strokeCap = StrokeCap.round;
    canvas.drawPoints(PointMode.points, points, _paint);
  }

  void _drawPointsWithLines(Canvas canvas) {
    _paint
      ..color = Colors.red
      ..style = PaintingStyle.stroke
      ..strokeWidth = 1
      ..strokeCap = StrokeCap.round;
    canvas.drawPoints(PointMode.lines, points, _paint);
  }

  void _drawPointLineWithPolygon(Canvas canvas) {
    _paint
      ..color = Colors.red
      ..style = PaintingStyle.stroke
      ..strokeWidth = 1
      ..strokeCap = StrokeCap.round;
    canvas.drawPoints(PointMode.polygon, points, _paint);
  }

  void _drawRawPoints(Canvas canvas) {
    Float32List pos = Float32List.fromList([
      -120, -20,-80, -80,-40,
      -40,0, -100,40, -140,
      80, -160,120, -100]);
    _paint
      ..color = Colors.red
      ..style = PaintingStyle.stroke
      ..strokeWidth = 10
      ..strokeCap = StrokeCap.round;
    canvas.drawRawPoints(PointMode.points, pos, _paint);
  }

  void _drawAxis(Canvas canvas, Size size) {
    _paint..color=Colors.blue..strokeWidth=1.5;
    canvas.drawLine(Offset(-size.width/2, 0) , Offset(size.width/2, 0),_paint);
    canvas.drawLine(Offset( 0,-size.height/2) , Offset( 0,size.height/2),_paint);
    canvas.drawLine(Offset( 0,size.height/2) , Offset( 0-7.0,size.height/2-10),_paint);
    canvas.drawLine(Offset( 0,size.height/2) , Offset( 0+7.0,size.height/2-10),_paint);
    canvas.drawLine(Offset(size.width/2, 0) , Offset(size.width/2-10, 7),_paint);
    canvas.drawLine(Offset(size.width/2, 0) , Offset(size.width/2-10, -7),_paint);
  }


  @override
  bool shouldRepaint(CustomPainter oldDelegate) => false;

  void _drawGrid(Canvas canvas, Size size) {
    _drawBottomRight(canvas, size);
    canvas.save();
    canvas.scale(1, -1); //沿x轴镜像
    _drawBottomRight(canvas, size);
    canvas.restore();

    canvas.save();
    canvas.scale(-1, 1); //沿y轴镜像
    _drawBottomRight(canvas, size);
    canvas.restore();

    canvas.save();
    canvas.scale(-1, -1); //沿原点镜像
    _drawBottomRight(canvas, size);
    canvas.restore();
  }

  void _drawBottomRight(Canvas canvas, Size size) {
    canvas.save();
    for (int i = 0; i < size.height / 2 / step; i++) {
      canvas.drawLine(Offset(0, 0), Offset(size.width / 2, 0), _gridPint);
      canvas.translate(0, step);
    }
    canvas.restore();

    canvas.save();
    for (int i = 0; i < size.width / 2 / step; i++) {
      canvas.drawLine(Offset(0, 0), Offset(0, size.height / 2), _gridPint);
      canvas.translate(step , 0);
    }
    canvas.restore();
  }


}