Java Can'；不要跨类更改JLabel

我有一个涉及一些基本JavaGUI的多类项目。我将使用10个类创建贷款计算器（其中6个是JPanel子类、一个计算类、一个CombinedPanels类、一个LoanCalculatorGUI类，该类创建CombinedPanels类和calculation类的实例，以及一个驱动程序）。我必须在一个JPanel子类（ActionButtons）中创建一个重置按钮，然后在另一个JPanel子类（PaymentInformation）中更改一个私有JLabel。下面是ActionButtons类：

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JPanel;


@SuppressWarnings("serial")
public class ActionButtons extends JPanel{
private JButton calc, reset, exit;
private JPanel actionButtons;
public ActionButtons(){
    PaymentInformation pi = new PaymentInformation();
    actionButtons = new JPanel(new GridLayout(1, 3, 20, 20));
    calc = new JButton("Calculate");
    reset = new JButton("Reset");
    exit = new JButton("Exit");
    actionButtons.add(calc);
    actionButtons.add(reset);
    actionButtons.add(exit);
    actionButtons.setBorder(BorderFactory.createTitledBorder("Action Buttons"));

    //Add ActionListeners
    calc.addActionListener(new ButtonListener());
    reset.addActionListener(new ButtonListener());
    exit.addActionListener(new ButtonListener());

}

public JPanel getGUI(){
    return actionButtons;
}



private class ButtonListener implements ActionListener{
    public void actionPerformed(ActionEvent e) {
        PaymentInformation pi = new PaymentInformation();
        if(e.getActionCommand().equals("Exit")){
            System.exit(0);
        }
        if(e.getActionCommand().equals("Reset")){
            pi.changeValues("0.0");
        }
        if(e.getActionCommand().equals("Calculate")){
            //TODO DO CALCULATIONS 
        }

    }

  }
}

以及PaymentInformation类：

import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.JLabel;
import javax.swing.JPanel;


 @SuppressWarnings("serial")
 public class PaymentInformation extends JPanel{
//Declare variables
private JPanel payInfo;
private JLabel loanAmt, monthPay, totalPay, loanVal, monthVal, totalVal;

public PaymentInformation(){
    //Give panel layout
    payInfo = new JPanel(new GridLayout(3, 2));
    //Give titles, set alignment
    loanAmt = new JLabel("Total Loan Amount:  $", JLabel.LEFT);
    monthPay = new JLabel("Monthly Payment:  $", JLabel.LEFT);
    totalPay = new JLabel("Total Payment:  $", JLabel.LEFT);
    loanVal = new JLabel("5.0", JLabel.RIGHT);
    monthVal = new JLabel("0.0", JLabel.RIGHT);
    totalVal = new JLabel("0.0", JLabel.RIGHT);
    //Add stuff to JPanel
    payInfo.add(loanAmt);
    payInfo.add(loanVal);
    payInfo.add(monthPay);
    payInfo.add(monthVal);
    payInfo.add(totalPay);
    payInfo.add(totalVal);
    //Set border
    payInfo.setBorder(BorderFactory.createTitledBorder("Payment Information"));
}
//Method to get the JPanel
public JPanel getGUI(){
    return payInfo;
}

public void changeValues(String val){
    loanVal.setText(val);
 }
}

我试图使用PaymentInformation中的setValue方法来更改JLabel的文本，但单击reset按钮时它保持不变（在“5.0”）。我不确定是否需要这样做，但CombinedPanels类（获取所有JLabel子类并将它们放入JFrame中）如下所示：

最后，这里是GUI的一个图像：

即使“5.0”JLabel应更改为“0.0”，当点击重置时，它仍保持不变。但是，“退出”按钮可以正常工作

很抱歉出现了文字墙，但这个问题快把我逼疯了。任何帮助或解释都将不胜感激。提前谢谢。

试试这个

public void changeValues(String val){
    loanVal=new JLabel(val, JLabel.RIGHT);
 }

---

您有3个不同的

PaymentInformation

实例。第一个在

组合面板

类中（显示的一个），一个在

操作按钮

类中，一个在

按钮列表器

类中。只更改最后一个（不可见）的值

因此，一种解决方案是将

组合面板

类的（可见的）

pi

传递给

ActionButtons

类，并在该实例上调用

changeValues（）

相关代码（已更改）：

---

不适合我。请注意，您可以在更改一点发布的代码后，先自己尝试一下。这很有效！我明白你的意思。谢谢你的帮助。

public void changeValues(String val){
    loanVal=new JLabel(val, JLabel.RIGHT);
 }

public CombinedPanels() {
    setTitle("Auto Loan Calculator");
    setSize(700, 500);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLayout(new BorderLayout());
    JPanel center = new JPanel(new GridLayout(2, 2, 20, 20));

    // Add other classes to this layout
    PaymentInformation pi = new PaymentInformation();
    ActionButtons ab = new ActionButtons(pi);
    add(ab.getGUI(), BorderLayout.SOUTH);
    // Add center JPanel to the center of BorderLayout
    add(center, BorderLayout.CENTER);
    // Continue with adding rest of classes to center JPanel
    center.add(pi.getGUI());
    setVisible(true);
}

public class ActionButtons extends JPanel {
    private JButton calc, reset, exit;
    private JPanel actionButtons;
    PaymentInformation pi;

    public ActionButtons(PaymentInformation pi) {
        this.pi = pi;
        actionButtons = new JPanel(new GridLayout(1, 3, 20, 20));
        calc = new JButton("Calculate");
        reset = new JButton("Reset");
        exit = new JButton("Exit");
        actionButtons.add(calc);
        actionButtons.add(reset);
        actionButtons.add(exit);
        actionButtons.setBorder(BorderFactory.createTitledBorder("Action Buttons"));

        // Add ActionListeners
        calc.addActionListener(new ButtonListener());
        reset.addActionListener(new ButtonListener());
        exit.addActionListener(new ButtonListener());

    }

    public JPanel getGUI() {
        return actionButtons;
    }

    private class ButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            if (e.getActionCommand().equals("Exit")) {
                System.exit(0);
            }
            if (e.getActionCommand().equals("Reset")) {
                pi.changeValues("0.0");
            }
            if (e.getActionCommand().equals("Calculate")) {
                // TODO DO CALCULATIONS
            }

        }

    }
}