为什么条形图不能执行？

Question

我不确定我要去哪里错。我正在创建一个程序，该程序需要4个月的销售数字并将其置于条形图上。我在public void windowClosing中获得了maint字符串中的@override请求。当我编译它说

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 

任何帮助表示赞赏。

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

变化

public class BarGraph extends JFrame 

到

public class BarGraph extends JPanel 

你有它的方式，BarGraph是JFrame，你不能添加JFrame到JFrame。