在饼图切片中间绘制带三角形的饼图

Question

我想画一个饼图，饼图切片中间有一个三角形。此刻我在切片中间画了一个带有切片和三角形的piechat，但是三角形不在直角。我需要知道如何以正确的方式放置三角形。我的代码和结果：

import java.awt.*;
import java.awt.geom.Ellipse2D;
import javax.swing.*;

class Slice {

   double value;
   Color color;
   public Slice(double value, Color color) {  
      this.value = value;
      this.color = color;
   }
}

class PieChart extends JPanel {

    private Color a = Color.RED;
    private Color b = Color.BLUE;
    private Color c = Color.YELLOW;
    Slice[] slices = { 
               new Slice(60, a),
               new Slice(100, b),
               new Slice(200, c)
    };

    public PieChart(){

    }

    @Override
    protected void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        super.paintComponent(g2d);
        this.setBackground(new Color(255,255,255));

        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        double total = 0.0D;
        for (int i = 0; i < slices.length; i++) {
            total += slices[i].value;
        }

        double curValue = 90.0D;
        int startAngle = 0;

        for (int i = 0; i < slices.length; i++) {
            startAngle = (int) (curValue * 360 / total);
            int arcAngle = (int) (slices[i].value * 360 / total);
            g2d.setColor(slices[i].color);
            g2d.fillArc(20, 20, 200, 200, startAngle, arcAngle);

            g2d.setPaint(Color.BLACK);
            int x = (int)(110+100*Math.cos(((-(startAngle+(arcAngle/2)))*Math.PI)/180));
            int y = (int)(110+100*Math.sin(((-(startAngle+(arcAngle/2)))*Math.PI)/180));

            Polygon p = new Polygon(new int[] {x, x+14, x+7}, new int[] {y, y, y-14}, 3); // this values seems to be important
            g2d.draw(p);
            g2d.fill(p);

            curValue += slices[i].value;
        }
    }
}

编辑：应该是这样的：

Answer 1

这里我做了一个解决方案（稍微改变一下算法）：

public class Chart {
public static void main(String[] args) {
    JFrame frame= new JFrame();
    frame.add(new PieChart());
    frame.setSize(new Dimension(400, 400));
    frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
    EventQueue.invokeLater( () ->{
        frame.setVisible(true);
    });
}

public static class Slice {
    double value;
    Color color;

    public Slice(double value, Color color) {
        this.value = value;
        this.color = color;
    }
}

public static class  PieChart extends JPanel {

    private static final long serialVersionUID = 1L;
    private Color a = Color.RED;
    private Color b = Color.BLUE;
    private Color c = Color.YELLOW;
    Slice[] slices = { new Slice(60, a), new Slice(100, b),
            new Slice(200, c) };

    public PieChart() {

    }

    @Override
    protected void paintComponent(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        super.paintComponent(g2d);

        this.setBackground(Color.WHITE);
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

        int upperLeftX = 20;
        int upperLeftY = 20;
        int r = 100;
        int startAngle = 0;


        double curValue = 0.0;

        for (int i = 0; i < slices.length; i++) {
            startAngle = (int) curValue ;
            int arcAngle = (int) slices[i].value ;
            g2d.setColor(slices[i].color);
            g2d.fillArc(upperLeftX, upperLeftY, r*2, r*2, startAngle, arcAngle);

            g2d.setPaint(Color.BLACK);

            double qi = curValue+slices[i].value/2;

            int x = upperLeftX + r + (int)(Math.cos(qi*Math.PI/180)*r);
            int y = upperLeftY + r - (int)(Math.sin(qi*Math.PI/180)*r);
            //point touching the circle (x,y)->half point of the base               
            int x1 = x - (int)(7*Math.sin(qi*Math.PI/180));
            int y1 = y - (int)(7*Math.cos(qi*Math.PI/180));

            int x2 = x + (int)(7*Math.sin(qi*Math.PI/180));
            int y2 = y + (int)(7*Math.cos(qi*Math.PI/180));

            int x3 = upperLeftX + r + (int)(Math.cos(qi*Math.PI/180)*(r+12));
            int y3 = upperLeftY + r - (int)(Math.sin(qi*Math.PI/180)*(r+12));


            Polygon p = new Polygon(new int[] { x1, x2, x3  },
                    new int[] { y1, y2, y3 }, 3); // this values seems to
                                                    // be important

            g2d.draw(p);
            g2d.fill(p);

            curValue += slices[i].value;
        }
    }
}
}

Answer 2

我制作了从 0 点钟开始的第一个弧线（我想你是故意这样做的）。

由于您使用的 fillArc 需要 ints，向下舍入的 doubles 可能不会加起来等于全部数量，并且切片之间会有间隙：

相反，使用 Arc2D.Double 以获得更好的精度：

class Slice {

    double value;
    Color color;

    public Slice(double value, Color color) {

        this.value = value;
        this.color = color;
    }

    public Color getColor() {

        return color;
    }

    public double getValue() {

        return value;
    }
}

class PieChart extends JPanel {

    private final int SIZE = 500, START = 40, START_DEG = 90;
    private final int TRIG_HBASE = 66, TRIG_HEIGHT = 36;
    private final int x0 =(START + SIZE / 2), y0 = START;
    private final Polygon poly;

    private Color a = Color.RED;
    private Color b = Color.BLUE;
    private Color c = Color.YELLOW;
    Slice[] slices = {new Slice(65, a), new Slice(123, b), new Slice(212, c)};

    PieChart() {

        setBackground(Color.WHITE);

        int x1 = x0 + TRIG_HBASE,  y1 = y0;
        int x2 = x0 - TRIG_HBASE,  y2 = y0;
        int x3 = x0,               y3 = y0 - TRIG_HEIGHT;
        poly = new Polygon(new int[] {x1, x2, x3}, new int[] {y1, y2, y3}, 3);
    }

    @Override
    protected void paintComponent(Graphics g) {

        Graphics2D g2d = (Graphics2D) g;
        super.paintComponent(g2d);

        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        g2d.setColor(Color.LIGHT_GRAY);
        g2d.fillRect(START, START, SIZE, SIZE);

        double total = 0d;
        for (Slice slice : slices) {
            total += slice.getValue();
        }

        double startAngle = START_DEG;
        double arcAngle, centerAngle;
        double x, y;

        for (Slice slice : slices) {
            arcAngle = (slice.getValue() * 360 / total);
            g2d.setColor(slice.getColor());
            g2d.fill(new Arc2D.Double(START, START, SIZE, SIZE, startAngle, arcAngle, Arc2D.PIE));

            centerAngle = Math.toRadians(((startAngle - START_DEG) + arcAngle / 2));
            x = (START + SIZE / 2 * (1 - Math.sin(centerAngle)));
            y = (START + SIZE / 2 * (1 - Math.cos(centerAngle)));

            AffineTransform trans = AffineTransform.getTranslateInstance(x - x0, y - y0);
            AffineTransform rot = AffineTransform.getRotateInstance(-centerAngle, x, y);
            Shape s = trans.createTransformedShape(poly);
            s = rot.createTransformedShape(s);

            g2d.setColor(slice.getColor().darker());
            g2d.fill(s);

            startAngle += arcAngle;
        }
    }

    @Override
    public Dimension getPreferredSize() {

        return new Dimension(START * 2 + SIZE, START * 2 + SIZE);
    }
}

poly作为基本三角形，底面以0点为中心，面朝上。每条弧线平移和变换此多边形（的副本），使其底边以弧长的中心为中心并指向外。

备注：

不要在paintComponent里面调用setBackground，在外面调用。它会导致绘制机制在每次重绘时自动绘制背景。如果你把它放在里面，你只是在每次重绘时覆盖指令。或者，您可以使用 g.clearRect 将背景设置为白色（或 fillRect 设置不同的颜色）。
覆盖面板的 getPreferredSize 方法以与其内容兼容。
使用常量 (final) 而不是行内数字。这样你只需要在一个地方改变它们，所有的依赖都被考虑在内。
Slice 可以使用 getter 方法（通常优于直接字段访问），并且它还允许 for each 循环。
使用 doubles 并且只在最后一点转换为 int，否则你会失去精度（你将你的角度转换为 int 然后将它们用作 double 参数).
Math.toRadians和Math.toDegrees值得结识
我将三角形变宽以显示它们如何与圆弧相交，更改 TRIG 常量以适应它们的大小。我还给它们上色以知道哪个三角形属于哪个弧。
我为弧线添加了背景，以便更好地查看周长。

这是使用您的参数的结果（没有特殊着色）：

private final int SIZE = 200, START = 20, START_DEG = 90;
private final int TRIG_HBASE = 7, TRIG_HEIGHT = 14;

在饼图切片中间绘制带三角形的饼图

Draw PieChart with triangle in the middle of PieChart slice

java

swing

draw

pie-chart

paintcomponent