Question

之前我问了一个类似的问题，但是我遇到了不同代码的问题。当我运行该程序时，会弹出窗口，但labels，textboxes和button未显示。将非常感谢帮助！我正在使用Eclipse IDE。

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


public class MonthlySalesTax extends JFrame {
    private JPanel panel;               // A panel to hold everything
    private JTextField totalSales;      // To get total sales
    private JButton calcButton;         // Calculates everything

    // Constants for tax rates
    private final double COUNTY_RATE = 0.02;
    private final double STATE_RATE = 0.04;

    // Constants for window size
    private final int WINDOW_WIDTH = 360;
    private final int WINDOW_HEIGHT = 100;

    /**
     * Constructor
     */

    public MonthlySalesTax() {
        // Set the title.
        setTitle("Monthly Sales Tax Reporter");

        // Specify what happens when the close button is clicked.
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Build the panel that contains the other components.
        buildPanel();

        // Size and display the window
        setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
        setVisible(true);
    }

    /**
     * The buildPanel method creates a panel containing other components.
     */

    private void buildPanel() {

        // Create a label prompting for the total sales.
        JLabel totalSalesMsg = new JLabel("Enter the total sales:");

        //Create a text field for total sales.
        totalSales = new JTextField(10);

        // Create a button to click.
        calcButton = new JButton("Calculate Sales Tax");

        // Add an action listener to the button.
        calcButton.addActionListener(new CalcButtonListener());

        // Create a panel.
        panel = new JPanel();

        // Add the label, text field, and button to the panel.
        panel.add(totalSalesMsg);
        panel.add(totalSales);
        panel.add(calcButton);
    }

    /**
     * CalcButtonListener is an action listener class for the calcbutton           component.
     */

    private class CalcButtonListener implements ActionListener {
        /**
         * actionPerformed method
         * @param e An ActionEvent object.
         */

        public void actionPerformed(ActionEvent e) {
            double totalSalesAmount,            // To hold the total sales     amount
                    countyTaxAmount,            // To hold the county tax
                    stateTaxAmount,             // To hold the state tax
                    totalTaxAmount;             // To hold the total tax

            // Create a DecimalFormat object to format output.
            DecimalFormat dollar = new DecimalFormat("#,##0.00");

            // Get the total sales.
            totalSalesAmount = Double.parseDouble(totalSales.getText());

            // Calculate the county tax.
            countyTaxAmount = totalSalesAmount * COUNTY_RATE;

            // Calculate the state tax.
            stateTaxAmount = totalSalesAmount * STATE_RATE;

            // Calculate the total sales.
            totalTaxAmount = countyTaxAmount + stateTaxAmount;

            // Display the result.
            JOptionPane.showMessageDialog(null, "County Sales Tax: $" +
                                        dollar.format(countyTaxAmount) +
                                        "\nState Sales Tax: $" +
                                        dollar.format(stateTaxAmount) +
                                        "\nTotal Sales Tax: $" +
                                        dollar.format(totalTaxAmount));
        }
    }

    /**
     * The main method creates an instance of the SalesTax class,
     * causing it to display its window.
     */

    public static void main(String[] args) {
        MonthlySalesTax stx = new MonthlySalesTax();
    }
}

Answer 1

啊，我忘了按照你们的建议将面板添加到JFrame中。

很简单：

add(panel);

谢谢大家！

我的Java程序没有在窗口中显示GUI

1 个答案: