Question

我遇到以下代码的问题，我已经详细说明了我遇到的问题以及详细的问题，但以防这里的问题就在眼前。当我单击Show Table按钮时，它不会在表格中显示我的计算，但是如果我在If语句中的某些位置添加了一个writeline（“get working”），它就可以完美地运行。我只是不确定我需要做什么才能在桌子上显示计算。

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


/* 
 * Developer: 
 * Date: 2/8/2016
 * Purpose:Enter the Loan amount and number of years. Display on the table the Interest, Monthly Payment and total payment.
 *          in the number of years from a text field, and it should display the 
 *          monthly and total payment
 */
public class Exercise17_13 extends JFrame {

    // add Panes, Panels and Labels 
    JScrollPane jScrollPane1 = new JScrollPane();
    JPanel jPanel1 = new JPanel();
    JTextArea jta = new JTextArea();
    TitledBorder titledBorder;
    JLabel jlblNumberYears = new JLabel("Number of Years");
    JLabel jlbLoanAmount = new JLabel("Loan Amount");
    JTextField jtfNumberYears = new JTextField(3);
    JTextField jtfLoanAmount = new JTextField(8);

    ButtonGroup btg = new ButtonGroup();
    JButton jbtShowTable = new JButton();

    public Exercise17_13() {

        //sets a Border around the program
        titledBorder = new TitledBorder("");
        this.setSize(new Dimension(400, 300));
        jPanel1.setBorder(titledBorder);
        titledBorder.setTitle("");

        //add the actionListeners 
        jtfNumberYears.addActionListener(new java.awt.event.ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jtfNumberYears_actionPerformed(e);
            }
        });
            //set the ShowTable button to receive ActionListener
        jbtShowTable.setText("Show Table");
        jbtShowTable.addActionListener(new java.awt.event.ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jbtShowTable_actionPerformed(e);
            }
        });
            //set LoanAmount to receive ActionListener
        jtfLoanAmount.addActionListener(new java.awt.event.ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jtfLoanAmount_actionPerformed(e);
            }
        });
            //set each Panel to center using null
        add(jScrollPane1, BorderLayout.CENTER);
        jScrollPane1.getViewport().add(jta, null);
        add(jPanel1, BorderLayout.NORTH);
        jPanel1.add(jlbLoanAmount, null);
        jPanel1.add(jtfLoanAmount, null);
        jPanel1.add(jlblNumberYears, null);
        jPanel1.add(jtfNumberYears, null);
        jPanel1.add(jbtShowTable, null);
        btg.add(jbtShowTable);
    }
    //set the default frame of the program
    public static void main(String[] args) {
        Exercise17_13 frame = new Exercise17_13();
        frame.setTitle("Exercise 17_13");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 250);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
        //sets LoanAmount to an editable action field
    void jtfLoanAmount_actionPerformed(ActionEvent e) {
        jtfLoanAmount.setEditable(true);
    }
        //sets number of years to an editable action field
    void jtfNumberYears_actionPerformed(ActionEvent e) {
        jtfNumberYears.setEditable(true);
    }
        //sets the show table button  action performed variables
    void jbtShowTable_actionPerformed(ActionEvent e) {
        double number;
        double denomination;
        double x;
        double y;



        /* this part of the program is supposed to display the loanAmount and  loanYears calculation
         * but it currently does not display anything on the table. If I comment out the starting
         * if (jbtShowTable.isSelected()) then it displays the System.out.Println("working") just 
         * fine on the table but not the calculations. I am not sure where I went wrong with 
         * displaying the results on the table.
         */

        //this does calculations for the LoanAmount and Years and
        // if (jbtShowTable.isSelected()) {
        //System.out.println("working");
        if (e.getSource() == jtfLoanAmount) {
        double totalAmount = Double.parseDouble(jtfLoanAmount.getText().trim());
        jtfLoanAmount.setEditable(true);
        jtfNumberYears.setEditable(true);

            if (e.getSource() == jtfNumberYears) { //getSource returns the object on which the event initally occured
                double numOfYears = Double.parseDouble(jtfNumberYears.getText().trim());
                jtfLoanAmount.setEditable(false);
                jtfNumberYears.setEditable(false);
                for (double intRate = 5; intRate <= 8; intRate = Math.round((intRate + .125) * 1000.0) / 1000.0) {
                    number = intRate / 100.0 * totalAmount / 12;
                    x = -(12 * numOfYears);
                    y = (intRate / 100.0 / 12) + 1.0;
                    denomination = 1.0 - Math.pow(y, x);
                    jta.setText(new Double(intRate + " " + Math.round((number / denomination) * 100.0) / 100.0 + " "
                            + Math.round(((number / denomination) * 12 * numOfYears) * 100.0) / 100.0).toString());


                     }
                }
            }
        }

}

Answer 1

好吧，它有一些问题：

if (e.getSource() == ...)陈述的内容是什么？只有在按下按钮时才会调用该方法，无需检查事件的来源。此外，当源是两个不同的东西时，你只是执行真正的魔法。马上。
然后，您尝试从包含三个以空格分隔的数字的Double解析String。什么是甚至试图实现？
然后你也会为“foo”循环的每次迭代覆盖你的文本区域。 append（每行后可能附加换行符）效果更好。
至于jbtShowTable.isSelected：我不确定为什么认为这是必要的，因为您所使用的方法是由按钮注册的ActionListener调用的。如果调用此方法，则某人必须按下按钮。：）

我做了这些更改后，数字开始出现在“表格”中。如果它们是正确的我不知道，但至少你现在可以看到它们。：）

输入贷款金额和年数。在表格上显示利息，每月付款和总付款

1 个答案: