java - 为什么条形图不执行？

Question

我不太确定我哪里出了问题。我正在创建一个程序，获取 4 个人当月的销售数据并将其放在条形图上。我在 public void windowClosing 的 maint 字符串中收到一个 @override 请求。当我编译时它说

Exception in thread "main" java.lang.IllegalArgumentException: adding a window to a container
    at java.awt.Container.checkNotAWindow(Container.java:488)
    at java.awt.Container.addImpl(Container.java:1089)
    at java.awt.Container.add(Container.java:415)
    at BarGraph.main(BarGraph.java:115)
Java Result: 1

感谢任何帮助。

import java.util.Scanner;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;


public class BarGraph extends JFrame

{   
    private final double[] sales;
    private final String[] salesAssociate;
    private final String title;

    public BarGraph(double[] sale, String[] saleAssoc, String t)
    {
       sales = sale;
       salesAssociate = saleAssoc;
       title = t;
    }

   public void paintComponent(Graphics graphics)
    {
       super.paintComponents(graphics);
       if (sales == null || sales.length == 0)
       return;
       double minSales = 0;
       double maxSales = 0;
       for (int i = 0; i < sales.length; i++)
       {
         if (minSales > sales[i])
             minSales = sales[i];
         if (maxSales < sales[i])
             maxSales = sales[i];
       }
       Dimension dim = getSize();
       int clientWidth = dim.width;
       int clientHeight = dim.height;
       int barWidth = clientWidth / sales.length;
       Font titleFont = new Font("Book Antiqua", Font.BOLD, 15);
       FontMetrics titleFontMetrics = graphics.getFontMetrics(titleFont);
       Font labelFont = new Font("Book Antiqua", Font.PLAIN, 10);
       FontMetrics labelFontMetrics = graphics.getFontMetrics(labelFont);
       int titleWidth = titleFontMetrics.stringWidth(title);
       int q = titleFontMetrics.getAscent();
       int p = (clientWidth - titleWidth) / 2;
       graphics.setFont(titleFont);
       graphics.drawString(title, p, q);
       int top = titleFontMetrics.getHeight();
       int bottom = labelFontMetrics.getHeight();
       if (maxSales == minSales)
           return;
       double scale = (clientHeight - top - bottom) / (maxSales - minSales);
       q = clientHeight - labelFontMetrics.getDescent();
       graphics.setFont(labelFont);
       for (int j = 0; j < sales.length; j++)
       {
           int salesP = j * barWidth + 1;
           int salesQ = top;
           int height = (int) ((sales[j]) * scale);
           if (sales[j] >= 0)
               salesQ += (int) (sales[j] * scale);
           else
           {
             salesQ += (int) (maxSales * scale);
             height = -height; 
           }


       graphics.setColor(Color.BLUE);
       graphics.fill3DRect(salesP, salesQ, barWidth - 2, height, true);
       graphics.setColor(Color.black);
       graphics.draw3DRect(salesP, salesQ, barWidth - 2, height, true);
       int labelWidth = labelFontMetrics.stringWidth(salesAssociate[j]);
       p = j * barWidth + (barWidth - labelWidth) / 2;
       graphics.drawString(salesAssociate[j], p, q);

    }  
}

  public static void main(String[] args) 
  {
      JFrame frame = new JFrame();
      frame.setSize(350, 300);
      double[] sales = new double[4];
      String[] salesAssociate = new String[4];
      double carsSold1;
      double carsSold2;
   double carsSold3;
   double carsSold4;  



      Scanner input = new Scanner(System.in);
      System.out.println("How many cars did Pam sell for the month?");
      carsSold1 = input.nextInt();        
      System.out.println("How many cars did Leo sell for the month?");
      carsSold2 = input.nextInt();
      System.out.println("How many cars did Kim sell for the month?");
      carsSold3 = input.nextInt();
      System.out.println("How many cars did Bob sell for the month?");
      carsSold4 = input.nextInt();

      sales[0] = carsSold1;
      salesAssociate[0] = "Pam";

      sales[1] = carsSold2;
      salesAssociate[1] = "Leo";

      sales[2] = carsSold3;
      salesAssociate[2] = "Kim";

      sales[3] = carsSold4;
      salesAssociate[3] = "Bob";

      frame.getContentPane().add(new BarGraph(sales, salesAssociate, "Friendly Hal's Auto"));
            WindowListener winListener = new WindowAdapter()
      {
          public void windowClosing(WindowEvent event)
          {
              System.exit(0);
          }
      };
      frame.addWindowListener(winListener);
      frame.setVisible(true);
  }

}

Answer 1

改变

public class BarGraph extends JFrame

至

public class BarGraph extends JPanel

按照您的方式，BarGraph 是一个 JFrame，并且您无法将 JFrame 添加到 JFrame。