Java 示例 - 显示饼图

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  问题描述

  如何使用框架显示饼图？
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  解决方案

  以下示例显示了如何通过制作 Slices 类并根据切片创建弧来显示饼图。

  
  import java.awt.Color;
  import java.awt.Graphics;
  import java.awt.Graphics2D;
  import java.awt.Rectangle;
  import javax.swing.JComponent;
  import javax.swing.JFrame;
  class Slice {
     double value;
     Color color;
     public Slice(double value, Color color) {  
        this.value = value;
        this.color = color;
     }
  }
  class MyComponent extends JComponent {
     Slice[] slices = { 
        new Slice(5, Color.black), new Slice(33, Color.green), new Slice(20, Color.yellow), new Slice(15, Color.red) 
     };
     MyComponent() {}
     public void paint(Graphics g) {
        drawPie((Graphics2D) g, getBounds(), slices);
     }
     void drawPie(Graphics2D g, Rectangle area, Slice[] slices) {
        double total = 0.0D;
        
        for (int i = 0; i < slices.length; i++) {
           total += slices[i].value;
        }
        double curValue = 0.0D;
        int startAngle = 0;
        for (int i = 0; i < slices.length; i++) {
           startAngle = (int) (curValue * 360 / total);
           int arcAngle = (int) (slices[i].value * 360 / total);
           g.setColor(slices[i].color);
           g.fillArc(area.x, area.y, area.width, area.height, startAngle, arcAngle);
           curValue += slices[i].value;
        }
     }
  }
  public class Main {
     public static void main(String[] argv) {
        JFrame frame = new JFrame();
        frame.getContentPane().add(new MyComponent());
        frame.setSize(300, 200);
        frame.setVisible(true);
     }
  }
  

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  结果

  上面的代码示例将产生以下结果。

  
  Displays a piechart in a frame.
  

  以下是使用框架显示饼图的示例。

  
  import java.awt.Color;
  import java.awt.Graphics;
  import java.awt.Graphics2D;
  import java.awt.Rectangle;
  import javax.swing.JComponent;
  import javax.swing.JFrame;
  class Part {
     double value;
     Color color;
     
     public Part(double value, Color color) {
        this.value = value;
        this.color = color;
     }
  }
  class MyComponent extends JComponent {
     Part[] slices = { 
        new Part(15, Color.yellow), new Part(30, Color.white), new Part(25, Color.blue), new Part(30, Color.red) 
     }; 
     MyComponent() {
     }
     public void paint(Graphics g) {
        drawPie((Graphics2D) g, getBounds(), slices);
     } 
     void drawPie(Graphics2D g, Rectangle area, Part[] slices) {
        double total = 0.0D;
        for (int i = 0; i < slices.length; i++) {
           total += slices[i].value;
        } 
        double curValue = 0.0D;
        int startAngle = 0;
        for (int i = 0; i < slices.length; i++) {
           startAngle = (int) (curValue * 360 / total);
           int arcAngle = (int) (slices[i].value * 360 / total);
           
           g.setColor(slices[i].color);
           g.fillArc(area.x, area.y, area.width, area.height, startAngle, arcAngle);
           curValue += slices[i].value;
        } 
     }
  }
  public class Panel {
     public static void main(String[] argv) {
        JFrame frame = new JFrame();
        frame.getContentPane().add(new MyComponent());
        frame.setSize(300, 200);
        frame.setVisible(true);
     }
  }