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我已经正确地重新编码了我的 GUI，其中用户输入了初始余额、年利率和年数。它计算并输出 15 年的数字。IE (10000, 2.5, 5) 正确生成 5 个数字。现在的问题是，用户决定用不同的输入数字再试一次，之前输出的原来的5个数字保留在计算器中，第二次重试输出新的数字。我不确定这是否是它的假设？还是我想清除 5 个原始数字？

这是代码：否则，我对编码很好，只需要澄清一下。

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import java.text.DecimalFormat;

public class SavingAccountFrame extends JFrame{
private static final int FRAME_WIDTH = 400;
private static final int FRAME_HEIGHT = 500;
private static final int AREA_ROWS = 10;
private static final int AREA_COLUMNS = 30;
private static final double DEFAULT_RATE = 5;
private static final double INITIAL_BALANCE = 1000;

private JLabel amountLabel1;
private JLabel amountLabel2;
private JLabel amountLabel3;
private JTextField amountField1;
private JTextField amountField2;
private JTextField amountField3;
private JButton button;
private JTextArea resultArea;
private JPanel panel;
//private BankAccount account;

public SavingAccountFrame(){
    //account = new BankAccount(INITIAL_BALANCE);
    resultArea = new JTextArea(AREA_ROWS, AREA_COLUMNS);
    resultArea.setEditable(false);
    createTextField();
    createButton();
    createPanel();
    setSize(FRAME_WIDTH, FRAME_HEIGHT);
}

private void createTextField(){
    final int FIELD_WIDTH = 10;
    amountLabel1 = new JLabel("Initial Balance: ");
    amountField1 = new JTextField(FIELD_WIDTH);
    amountField1.setText("" + 100000);
    amountLabel2 = new JLabel("Annual Rate: ");
    amountField2 = new JTextField(FIELD_WIDTH);
    amountField2.setText("" + 3.5);
    amountLabel3 = new JLabel("Number of Years: ");
    amountField3 = new JTextField(FIELD_WIDTH);
    amountField3.setText("" + 15);
}

private void createButton(){
    button = new JButton("Calculate");
    class AddInterestListener implements ActionListener{
        public void actionPerformed(ActionEvent event){
            DecimalFormat df = new DecimalFormat("0.00");
            double interest;
            double balance = Double.parseDouble(amountField1.getText());
            double rate = Double.parseDouble(amountField2.getText());
            double years = Double.parseDouble(amountField3.getText());
            for(int i = 0; i < years; i++){
                interest = balance * rate / 100;
                balance = balance + interest;
                resultArea.append("$" + df.format(balance) + "\n");
            }
        }
    }

    ActionListener listener = new AddInterestListener();
    button.addActionListener(listener);
}

private void createPanel(){
    panel = new JPanel();
    panel.add(amountLabel1);
    panel.add(amountLabel2);
    panel.add(amountLabel3);
    panel.add(amountField1);
    panel.add(amountField2);
    panel.add(amountField3);
    panel.add(button);
    JScrollPane scrollPane = new JScrollPane(resultArea);
    panel.add(scrollPane);
    add(panel);
}
}
4

1 回答 1

1

resultArea每次单击Calculate按钮时，您都将结果附加到

你有（至少）两个选择......

建立String输出值并使用resultArea.setText方法设置文本，这将清除该字段并将其替换为您提供的文本...

private void createButton(){
    button = new JButton("Calculate");
    class AddInterestListener implements ActionListener{
        public void actionPerformed(ActionEvent event){
            DecimalFormat df = new DecimalFormat("0.00");
            double interest;
            double balance = Double.parseDouble(amountField1.getText());
            double rate = Double.parseDouble(amountField2.getText());
            double years = Double.parseDouble(amountField3.getText());
            StringBuilder sb = new StringBuilder(128);
            for(int i = 0; i < years; i++){
                interest = balance * rate / 100;
                balance = balance + interest;
                sb.append("$" + df.format(balance) + "\n");
            }
            resultArea.setText(sb.toString());
        }
    }

    ActionListener listener = new AddInterestListener();
    button.addActionListener(listener);
}

或者在更新字段之前使用setText并传递它null或为空来清除它String

private void createButton(){
    button = new JButton("Calculate");
    class AddInterestListener implements ActionListener{
        public void actionPerformed(ActionEvent event){
            DecimalFormat df = new DecimalFormat("0.00");
            double interest;
            double balance = Double.parseDouble(amountField1.getText());
            double rate = Double.parseDouble(amountField2.getText());
            double years = Double.parseDouble(amountField3.getText());
            resultArea.setText(null);
            for(int i = 0; i < years; i++){
                interest = balance * rate / 100;
                balance = balance + interest;
                resultArea.append("$" + df.format(balance) + "\n");
            }
        }
    }

    ActionListener listener = new AddInterestListener();
    button.addActionListener(listener);
}
于 2013-11-06T02:43:52.097 回答