android - Flutter:如何画星星

Question

我正在尝试自定义我的容器形状，使其看起来像这样:

我试着用 customPaint 来做，但我不太了解这个小部件，所以我需要帮助。

我怎样才能画出这样的形状？ customPaint 是正确的解决方案吗？

Answer 1

您可以在下面复制粘贴运行完整代码
包的修改代码 https://pub.dev/packages/flutter_custom_clippers的
StarClipper https://github.com/lohanidamodar/flutter_custom_clippers/blob/master/lib/src/star_clipper.dart

代码 fragment

class StarClipper extends CustomClipper<Path>
 @override
   Path getClip(Size size) {
     ...
     double radius = halfWidth / 1.3;
...
Container(
      height: 200,
      width: 200,
      child: ClipPath(
        clipper: StarClipper(14),
        child: Container(
          height: 150,
          color: Colors.green[500],
          child: Center(child: Text("+6", style: TextStyle(fontSize: 50),)),
        ),
      ),
    ),

工作演示

完整代码

import 'package:flutter/material.dart';
import 'dart:math' as math;

class StarClipper extends CustomClipper<Path> {
  StarClipper(this.numberOfPoints);

  /// The number of points of the star
  final int numberOfPoints;

  @override
  Path getClip(Size size) {
    double width = size.width;
    print(width);
    double halfWidth = width / 2;

    double bigRadius = halfWidth;

    double radius = halfWidth / 1.3;

    double degreesPerStep = _degToRad(360 / numberOfPoints);

    double halfDegreesPerStep = degreesPerStep / 2;

    var path = Path();

    double max = 2 * math.pi;

    path.moveTo(width, halfWidth);

    for (double step = 0; step < max; step += degreesPerStep) {
      path.lineTo(halfWidth + bigRadius * math.cos(step),
          halfWidth + bigRadius * math.sin(step));
      path.lineTo(halfWidth + radius * math.cos(step + halfDegreesPerStep),
          halfWidth + radius * math.sin(step + halfDegreesPerStep));
    }

    path.close();
    return path;
  }

  num _degToRad(num deg) => deg * (math.pi / 180.0);

  @override
  bool shouldReclip(CustomClipper<Path> oldClipper) {
    StarClipper oldie = oldClipper as StarClipper;
    return numberOfPoints != oldie.numberOfPoints;
  }
}


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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
              height: 200,
              width: 200,
              child: ClipPath(
                clipper: StarClipper(14),
                child: Container(
                  height: 150,
                  color: Colors.green[500],
                  child: Center(child: Text("+6", style: TextStyle(fontSize: 50),)),
                ),
              ),
            ),

          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}