java - 我正在尝试在一个简单的银行系统上实现 'undo' JButton，它将撤消上次执行的操作

Question

我正在运行其余的代码，但我不确定在 ActionListener 中为撤消按钮做什么。我只有这个 Action 监听器

    private class UndoButtonHandler implements ActionListener{

    public void actionPerformed(ActionEvent e) {

    }

我将在下面发布 GUI 类的其余部分以供引用，因为这不是作业(它是，只是不在 GUI 中)，我感谢任何人可以给我的任何建议。

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


    public class BankGUI extends JFrame {
private JLabel checking;
private JLabel saving;
private JButton depChecking;
private JButton depSaving;
private JButton witChecking;
private JButton withSaving;
private JButton transferToSaving;
private JButton transferToChecking;
private JButton undo;
private JTextField checkingAmt;
private JTextField savingAmt;
private JTextField depositChk;
private JTextField depositSav;
private JTextField withChk;
private JTextField withSav;
private JTextField transChk;
private JTextField transSav;

public BankGUI() {
    super( "Bank Application" );
    setLayout(new FlowLayout() );

    checkingAmt = new JTextField(10);
    checkingAmt.setEditable(false);
    checkingAmt.setText("500.00");
    add( checkingAmt );

    savingAmt = new JTextField(10);
    savingAmt.setEditable(false);
    savingAmt.setText("0.00");
    add(savingAmt);

    checking = new JLabel( "                  Checking        ");
    add(checking);

    saving = new JLabel( "      Saving              " );
    add(saving);

    depChecking = new JButton( "  Deposit  " );
    add(depChecking);
    depChecking.addActionListener(new DepChkButtonHandler());

    depSaving = new JButton( "  Deposit  " );
    add(depSaving);
    depSaving.addActionListener(new DepSavButtonHandler());

    depositChk = new JTextField(10);
    depositChk.setEditable(true);
    add(depositChk);

    depositSav = new JTextField(10);
    depositSav.setEditable(true);
    add(depositSav);

    witChecking = new JButton( "  Withdraw  " );
    add(witChecking);
    witChecking.addActionListener(new WitChkButtonHandler());

    withSaving = new JButton( "  Withdraw  " );
    add(withSaving);
    withSaving.addActionListener(new WithSavButtonHandler());

    withChk = new JTextField(10);
    withChk.setEditable(true);
    add(withChk);

    withSav = new JTextField(10);
    withSav.setEditable(true);
    add(withSav);

    transferToSaving = new JButton( "  Transfer  " );
    add(transferToSaving);
    transferToSaving.addActionListener(new TranstoSavButtonHandler());

    transferToChecking = new JButton( "  Transfer  " );
    add(transferToChecking);
    transferToChecking.addActionListener(new TranstoChkButtonHandler());

    transSav = new JTextField(10);
    transSav.setEditable(true);
    add(transSav);

    transChk = new JTextField(10);
    transChk.setEditable(true);
    add(transChk);

    undo = new JButton( "  Undo  " );
    add(undo);
}

private class DepChkButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent arg0) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double depAmt = Double.parseDouble(depositChk.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt = deciFormat.format(depAmt + chkAmt);

        checkingAmt.setText(newAmt);

    }

}

private class DepSavButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double depAmt = Double.parseDouble(depositSav.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        String newAmt = deciFormat.format(depAmt + savAmt);

        savingAmt.setText(newAmt);

    }

}

private class WitChkButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent arg0) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double witAmt = Double.parseDouble(withChk.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt = deciFormat.format(chkAmt - witAmt);

        checkingAmt.setText(newAmt);

    }

}

private class WithSavButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double witAmt = Double.parseDouble(withSav.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        String newAmt = deciFormat.format(savAmt - witAmt);

        savingAmt.setText(newAmt);

    }

}

private class TranstoSavButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double transAmt = Double.parseDouble(transSav.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt1 = deciFormat.format(savAmt + transAmt);
        String newAmt2 = deciFormat.format(chkAmt - transAmt);
        savingAmt.setText(newAmt1);
        checkingAmt.setText(newAmt2);

    }

}

private class TranstoChkButtonHandler implements ActionListener{

    @Override
    public void actionPerformed(ActionEvent e) {
        DecimalFormat deciFormat = new DecimalFormat(); 
        deciFormat.setMaximumFractionDigits(2);
        double transAmt = Double.parseDouble(transChk.getText());
        double savAmt = Double.parseDouble(savingAmt.getText());
        double chkAmt = Double.parseDouble(checkingAmt.getText());
        String newAmt1 = deciFormat.format(savAmt - transAmt);
        String newAmt2 = deciFormat.format(chkAmt + transAmt);
        savingAmt.setText(newAmt1);
        checkingAmt.setText(newAmt2);

    }

}

private class UndoButtonHandler implements ActionListener{

    public void actionPerformed(ActionEvent e) {

    }
}

}

Answer 1

您需要决定撤消的深度。用户可以撤消最近 10 次操作，还是仅撤消最近一次操作？此决定将决定您是将最后一个操作存储为简单字段，还是存储为某种List 事务(某种Queue 也可以)。

您还应该将您的交易标准化为某种模型，该模型可以反射(reflect)您的应用程序支持的每种交易的详细信息。换句话说，您需要一个 Transaction 对象，其中包含诸如 amount、sourceAcct、destinationAcct 或您想要的字段去做吧。关键是这个 Transaction 对象需要能够表示用户可能想要在程序中执行(或撤消)的所有操作。

此 Transaction 对象将用于进行正常的记账(从帐户中添加或删除资金)，但在调整余额后，您将 Transaction 保存到您的 lastTransaction 字段或您的 transActions列表。

创建一个名为 undo 的方法并将其放入您的撤消处理程序中。当用户单击撤消按钮时，您的 undo 方法只会查看最近的事务并将其撤消。例如，如果交易是 100 美元的支票存款，当您撤消该交易时，您不会在支票中添加 100 美元，而是从支票中减去 100 美元。如果您正在处理交易列表，请确保在撤消交易后将其删除。