Flutter学习笔记 —— CustomPainter自定义画布绘制爱心

前言

最近在学习Flutter中 Canvas相关内容，今天尝试写了一个爱心Demo(程序员浪漫，表白神器！)，感兴趣可以学习一下，如果你有更好的方法欢迎评论

效果图

代码示例

包含注释，这里只提供自定义的CustomPainter类

import 'dart:math';
import "dart:ui" as ui;
import 'dart:ui';

import 'package:flutter/material.dart';

/**
 * @author Marinda
 * @date 2023/3/29 10:58
 * @desc 我的画板
 */
class MyCustomPainter extends CustomPainter{

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()..color = Colors.blue..strokeWidth = 20..isAntiAlias = true ..style = PaintingStyle.stroke ..strokeCap = StrokeCap.butt;
    double centerWidth = size.width / 2;
    double centerHeight = size.height / 2;
    Path path = Path();
    double width = size.width;
    double height = size.height;

    /*
     * 绘制心形逻辑
     * 1.绘制左半圆 addArc 默认从左到右进行绘制，并且抬笔重新画到右边
     * 2.ArcTo绘制右半圆，不抬笔连前左半圆结束点开始绘制
     * 3.接着从右半圆结束点绘制线段至中心结束点
     * 4.再从线段起始点绘制左半圆 ,这里还是使用arcTo绘制，因为使用addArc则视为抬笔，则从①结束点开始绘制，不链接
     * -100 是由于画圆会导致扩大，视觉差不居中
     */
    path.moveTo(centerWidth, centerHeight);
    path.addArc(Rect.fromLTWH(centerWidth-100, centerHeight, 100,100), 160 * (pi / 180), 200 * (pi / 180));
    path.arcTo(Rect.fromLTWH(centerWidth, centerHeight, 100,100), 180 * (pi / 180), 200 * (pi / 180),false);
    path.lineTo(centerWidth, centerHeight +200);
    path.arcTo(Rect.fromLTWH(centerWidth - 100, centerHeight, 100,100), 160 * (pi / 180), 200 * (pi / 180),false);
    canvas.drawPath(path, Paint()..color = Colors.red..strokeWidth = 4 ..style = PaintingStyle.stroke ..isAntiAlias = true);
    /*
     * @Author Marinda
     * @Description 绘制文字
     * @Date 15:18 2023/3/29
     **/
    ui.ParagraphBuilder paragraphBuilder = ui.ParagraphBuilder(ui.ParagraphStyle(fontSize: 20));
    ParagraphConstraints paragraphConstraints = ParagraphConstraints(width: 200);
    paragraphBuilder.pushStyle(ui.TextStyle(color: Colors.blue));
    paragraphBuilder.addText("XXX");
    Paragraph paragraph = paragraphBuilder.build()..layout(paragraphConstraints);
    canvas.drawParagraph(paragraph, Offset(centerWidth-20,centerHeight+70));

    /*
     * 绘制穿心路径
     */
    ui.Path linePath = Path();
    linePath.moveTo(centerWidth / 4, centerHeight+100);
    linePath.lineTo(centerWidth+220, centerHeight +100);
    //绘制当前线段向上箭头
    linePath.relativeLineTo(-20, -20);

    //绘制当前线段向下箭头
    canvas.drawLine(Offset(centerWidth + 220,centerHeight+100), Offset(centerWidth +200,centerHeight +125), Paint()..color = Colors.red..strokeWidth = 4 ..style = PaintingStyle.stroke ..isAntiAlias = true);

    canvas.drawPath(linePath, Paint()..color = Colors.red..strokeWidth = 4 ..style = PaintingStyle.stroke ..isAntiAlias = true..strokeMiterLimit = 3);
  }

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

}

温馨提示

请注意看注释，关于Canvas中绘制Path中对于addArc 和 arcTo的区别，一个是默认抬笔重新绘制 一个是可选抬笔状态！

结束语

关于 Flutter学习笔记 —— CustomPainter自定义画布绘制爱心 就写到这里，对你有帮助的话！

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谢谢你的观看！