Question

我迷失了如何在用户点击计算按钮后使用用户输入来创建图表。我是编程新手，推动正确的方向非常好。

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

public class worksheet5 extends JApplet implements ActionListener {

   double E, B, N;
   JLabel title, firstBalance, lastBalance, userBalance1, userBalance2,
         userBalance3, userBalance4, rateInvested, rateOfReturn;

   JTextField begBalance, endBalance, balance1, balance2, balance3, balance4,
         userRate, userReturn;
   Button b;

   public void init() {
      setLayout(new BorderLayout());
      setUpTitle();
      setUpMiddle();
      setUpBottom();
   }

   public void setUpTitle() {
      title = new JLabel("Calculate your return rate", JLabel.CENTER);
      add(title, BorderLayout.NORTH);
   }

   public void setUpMiddle() {

      firstBalance = new JLabel("What was your starting balance?");
      begBalance = new JTextField("", 15);
      userBalance1 = new JLabel("What was your balance after year one?");
      balance1 = new JTextField("", 15);
      userBalance2 = new JLabel("What was your balance after year two?");
      balance2 = new JTextField("", 15);
      userBalance3 = new JLabel("What was your balance after year three?");
      balance3 = new JTextField("", 15);
      userBalance4 = new JLabel("What was your balance after year four?");
      balance4 = new JTextField("", 15);
      lastBalance = new JLabel("What was your ending balance year five?");
      endBalance = new JTextField("", 15);
      rateInvested = new JLabel("How many years did you invest?");
      userRate = new JTextField("", 15);

      JPanel pane1 = new JPanel(new FlowLayout());
      pane1.add(firstBalance);
      pane1.add(begBalance);
      JPanel pane2 = new JPanel(new FlowLayout());
      pane2.add(userBalance1);
      pane2.add(balance1);
      pane2.add(userBalance2);
      pane2.add(balance2);
      pane2.add(userBalance3);
      pane2.add(balance3);
      pane2.add(userBalance4);
      pane2.add(balance4);
      pane2.add(lastBalance);
      pane2.add(endBalance);
      JPanel pane3 = new JPanel(new FlowLayout());
      pane3.add(rateInvested);
      pane3.add(userRate);

      JPanel mainPane = new JPanel(new GridLayout(3, 1));
      mainPane.add(pane1);
      mainPane.add(pane2);
      mainPane.add(pane3);
      add(mainPane, BorderLayout.CENTER);
   }

   public void setUpBottom() {

      rateOfReturn = new JLabel("Your rate of return is :");
      userReturn = new JTextField("", 15);
      b = new Button("calculate");
      b.addActionListener(this);
      JPanel pane4 = new JPanel(new FlowLayout());
      pane4.add(rateOfReturn);
      pane4.add(userReturn);
      pane4.add(b);
      add(pane4, BorderLayout.SOUTH);
   }

   public void actionPerformed(ActionEvent ae) {
      if (ae.getSource() == b) {
         E = Double.parseDouble(endBalance.getText());
         B = Double.parseDouble(begBalance.getText());
         N = Double.parseDouble(userRate.getText());
         double R = Math.pow(E / B, 1.0 / N) - 1;

         userReturn.setText("" + R * 100 + "%");

      }
   }
}

class BarChart extends worksheet5 {
   int n;
   String year[];
   int value[];

   public void graph() {
      n = 5;
      year = new String[n];
      value = new int[n];

      year[0] = getParameter("year0");
      year[1] = getParameter("year1");
      year[2] = getParameter("year2");
      year[3] = getParameter("year3");
      year[4] = getParameter("year4");

      value[0] = Integer.parseInt(begBalance.getText());
      value[1] = Integer.parseInt(balance1.getText());
      value[2] = Integer.parseInt(balance2.getText());
      value[3] = Integer.parseInt(balance3.getText());
      value[4] = Integer.parseInt(balance4.getText());

   }

   public void paint(Graphics g) {
      Font font = new Font("Arial", Font.BOLD, 15);
      g.setFont(font);
      for (int i = 0; i < n; i++) {
         g.setColor(Color.BLUE);
         g.drawString(year[i], 20, i * 50 + 30);
         g.setColor(Color.RED);
         g.fillRect(70, i * 50 + 10, value[i], 40);
         g.drawString(String.valueOf(value[i]) + "%", 180, i * 50 + 35);
      }

      String msg = "Bar Chart from Year 2001 - 2005";
      g.setColor(Color.darkGray);

      font = new Font("Arial", Font.BOLD, 20);
      g.setFont(font);
      g.drawString(msg, 50, 300);
   }
}

Answer 1

建议：

您的工作表5类应重命名为WorkSheet5，以符合Java naming conventions。变量名都应以较低的字母开头，而类名以大写字母开头。此外，您应该避免使用简单的变量名称，例如b或s，除非它们被用于琐碎的目的，例如for循环的索引。而是使用具有某种含义的名称，以便您的代码成为自我评论。遵循这些建议以及遵循良好的代码格式化实践将允许其他人（例如我们！）更好地理解您的代码，更重要的是，将允许您的未来自我更好地理解您在6个月前撰写代码。
BarChart不应扩展工作表5，但应扩展JPanel。
您应该使用BarChart的paintComponent方法覆盖
并在此方法之前使用@Override注释，以确保它是有效的覆盖。
paintComponent(Graphics g)方法覆盖的第一行应该是对super的方法的调用，以允许Java清理任何脏像素：super.paintComponent(g);
您将从ActionListener中的文本字段中提取数据，而不是在BarChart中提取数据。然后，您将数据传递到BarChart实例。
为BarChart提供一个构造函数，该构造函数接收将用于创建图形的数字。
然后在paintComponent方法中使用这些数字来尝试绘制条形图。
然后在某个地方显示BarChart JPanel，可能在当前applet中使用CardLayout，可能在JOptionPane中。

我需要帮助在applet中显示来自用户输入的图表

1 个答案: