为什么代码会创建两个JDialog对象？

Question

我在项目中创建了一个JFrame，它从JComboBox获取输入。我已将EventListener添加到组合框中。 I.E.当我选择＆＃34;其他＆＃34;来自ment的项目，它应该创建一个JDialog的实例。但它创造了两个实例。谁能告诉我为什么会这样？

主要

package app;

import java.awt.BorderLayout;

public class Main extends JFrame {

private JPanel contentPane;
private JTextField textField;
private JTextField textField_1;
private JTextField textField_2;
private JTextField textField_3;
private JLabel lblCallType;
private JComboBox calltypecombo;
private JPanel panel;
private JLabel lblCallMode;
private JComboBox callmodecombo;
private JLabel lblSource;
private JComboBox sourcecombo;
private JLabel lblItemName;
private JTextField textField_4;
private JLabel lblItemMag;
private JTextField textField_5;
private JLabel lblItemDetails;
private JLabel lblItemModel;
private JTextField textField_6;
private JLabel lblItemSrno;
private JTextField textField_7;
private JLabel lblBookingDescription;
private JSeparator separator_1;
private JLabel lblCustomerDetails;
private JLabel lblCustomerName;
private JTextField textField_9;
private JLabel lblAddress;
private JLabel lblContactNo;
private JTextField textField_11;
private JLabel lblEmailId;
private JTextField textField_12;
private JTextArea textArea_1;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Main frame = new Main();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the frame.
 */
public Main() {
    setTitle("F1 Services & Solutions");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(300, 300, 1000, 600);     
    contentPane = new JPanel();
    contentPane.setForeground(Color.RED);
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);

    JLabel lblSrno = new JLabel("Sr.No ");
    lblSrno.setBounds(10, 11, 49, 22);
    contentPane.add(lblSrno);

    textField = new JTextField();
    textField.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField.setBounds(91, 12, 106, 20);
    contentPane.add(textField);
    textField.setColumns(10);

    JLabel lblCallDate = new JLabel("Call Date");
    lblCallDate.setBounds(10, 45, 71, 14);
    contentPane.add(lblCallDate);

    textField_1 = new JTextField();
    textField_1.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_1.setBounds(91, 42, 106, 22);
    contentPane.add(textField_1);
    textField_1.setColumns(10);

    JLabel lblCallTime = new JLabel("Call Time");
    lblCallTime.setBounds(291, 45, 58, 14);
    contentPane.add(lblCallTime);

    textField_2 = new JTextField();
    textField_2.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_2.setBounds(359, 40, 97, 22);
    contentPane.add(textField_2);
    textField_2.setColumns(10);

    JLabel lblRmaNo = new JLabel("RMA No.");
    lblRmaNo.setBounds(738, 45, 75, 14);
    contentPane.add(lblRmaNo);

    textField_3 = new JTextField();
    textField_3.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_3.setBounds(805, 41, 86, 20);
    contentPane.add(textField_3);
    textField_3.setColumns(10);

    lblCallType = new JLabel("Call Type");
    lblCallType.setBounds(10, 438, 70, 14);
    contentPane.add(lblCallType);

    String[] type={"Within Warranty","Out Of Warranty"};
    calltypecombo = new JComboBox(type);
    calltypecombo.setBounds(91, 435, 129, 20);
    contentPane.add(calltypecombo);

    lblCallMode = new JLabel("Call Mode");
    lblCallMode.setBounds(302, 438, 58, 14);
    contentPane.add(lblCallMode);

    String[] mode={"On Site","Carry In"};
    callmodecombo = new JComboBox(mode);
    callmodecombo.setBounds(370, 435, 86, 20);
    contentPane.add(callmodecombo);

    lblSource = new JLabel("Source");
    lblSource.setBounds(501, 45, 58, 14);
    contentPane.add(lblSource);

    String[] source={"F1 Smart","Asus","Other"};
    sourcecombo = new JComboBox(source);
    sourcecombo.addItemListener(new ItemListener() {
        public void itemStateChanged(ItemEvent arg0) {
            String state=(String) sourcecombo.getSelectedItem();
            if(state.equals("F1 Smart") || state.equals("Asus"))
            {                   
                calltypecombo.setEnabled(true); 

            }
            else if(state.equals("Other"))
            {                   
                calltypecombo.setEnabled(false);
                OtherCharges.main(null);                    

            }
        }
    });
    sourcecombo.setBounds(600, 42, 86, 20);
    contentPane.add(sourcecombo);

    lblItemName = new JLabel("Item Name");
    lblItemName.setBounds(10, 156, 71, 14);
    contentPane.add(lblItemName);

    textField_4 = new JTextField();
    textField_4.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_4.setBounds(91, 153, 106, 20);
    contentPane.add(textField_4);
    textField_4.setColumns(10);

    lblItemMag = new JLabel("Item MAG");
    lblItemMag.setBounds(10, 191, 71, 14);
    contentPane.add(lblItemMag);

    textField_5 = new JTextField();
    textField_5.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_5.setBounds(91, 188, 106, 20);
    contentPane.add(textField_5);
    textField_5.setColumns(10);

    JSeparator separator = new JSeparator();
    separator.setBounds(10, 124, 964, 2);
    contentPane.add(separator);

    lblItemDetails = new JLabel("Item Details:");
    lblItemDetails.setForeground(Color.RED);
    lblItemDetails.setBounds(10, 128, 71, 14);
    contentPane.add(lblItemDetails);

    lblItemModel = new JLabel("Item Model");
    lblItemModel.setBounds(10, 236, 71, 14);
    contentPane.add(lblItemModel);

    textField_6 = new JTextField();
    textField_6.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_6.setBounds(91, 233, 106, 20);
    contentPane.add(textField_6);
    textField_6.setColumns(10);

    lblItemSrno = new JLabel("Item Sr.No.");
    lblItemSrno.setBounds(10, 277, 75, 14);
    contentPane.add(lblItemSrno);

    textField_7 = new JTextField();
    textField_7.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_7.setBounds(91, 274, 106, 20);
    contentPane.add(textField_7);
    textField_7.setColumns(10);

    lblBookingDescription = new JLabel("Booking Desc.");
    lblBookingDescription.setBounds(10, 315, 93, 14);
    contentPane.add(lblBookingDescription);

    lblCustomerDetails = new JLabel("Customer Details :");
    lblCustomerDetails.setForeground(Color.RED);
    lblCustomerDetails.setBounds(501, 128, 129, 14);
    contentPane.add(lblCustomerDetails);

    lblCustomerName = new JLabel("Customer Name");
    lblCustomerName.setBounds(501, 156, 93, 14);
    contentPane.add(lblCustomerName);

    textField_9 = new JTextField();
    textField_9.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_9.setBounds(602, 156, 166, 20);
    contentPane.add(textField_9);
    textField_9.setColumns(10);

    lblAddress = new JLabel("Address");
    lblAddress.setBounds(501, 191, 67, 14);
    contentPane.add(lblAddress);

    lblContactNo = new JLabel("Contact No.");
    lblContactNo.setBounds(501, 277, 71, 14);
    contentPane.add(lblContactNo);

    textField_11 = new JTextField();
    textField_11.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_11.setBounds(602, 273, 166, 20);
    contentPane.add(textField_11);
    textField_11.setColumns(10);

    lblEmailId = new JLabel("Email ID ");
    lblEmailId.setBounds(501, 315, 75, 14);
    contentPane.add(lblEmailId);

    textField_12 = new JTextField();
    textField_12.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 11));
    textField_12.setBounds(602, 311, 166, 20);
    contentPane.add(textField_12);
    textField_12.setColumns(10);

    JButton btnRegister = new JButton("Register");
    btnRegister.setBounds(413, 493, 89, 23);
    contentPane.add(btnRegister);

    JTextArea textArea = new JTextArea();
    textArea.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 13));
    textArea.setLineWrap(true);
    textArea.setBounds(602, 186, 166, 74);
    contentPane.add(textArea);

    textArea_1 = new JTextArea();
    textArea_1.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 13));
    textArea_1.setLineWrap(true);
    textArea_1.setBounds(91, 310, 206, 111);
    contentPane.add(textArea_1);


}
}

JDialog Class是：

package app;

import java.awt.BorderLayout;
import java.awt.FlowLayout;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;

import java.awt.Color;

import javax.swing.JLabel;

import java.awt.Font;
import java.awt.SystemColor;

import javax.swing.JComboBox;
import javax.swing.JTextField;

import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import java.awt.event.InputMethodListener;
import java.awt.event.InputMethodEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class OtherCharges extends JDialog {

private final JPanel contentPanel = new JPanel();
private JTextField from;
private JTextField to;
private JTextField distance;
private JTextField totalcost;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    try {
        OtherCharges dialog = new OtherCharges();
        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);          
    } catch (Exception e) {
        e.printStackTrace();
    }
}

/**
 * Create the dialog.
 */
public OtherCharges() {
    setVisible(true);
    setBounds(100, 100, 1000,700);
    getContentPane().setLayout(new BorderLayout());
    contentPanel.setBackground(Color.WHITE);
    contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
    getContentPane().add(contentPanel, BorderLayout.CENTER);
    contentPanel.setLayout(null);

    JLabel lblYouWillBe = new JLabel("You Will Be Charged As Per Taxes & LBT");
    lblYouWillBe.setForeground(Color.BLACK);
    lblYouWillBe.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 16));
    lblYouWillBe.setBounds(342, 11, 324, 22);
    contentPanel.add(lblYouWillBe);

    JLabel lblFillYourDetails = new JLabel("Fill Your Details Below ");
    lblFillYourDetails.setForeground(Color.RED);
    lblFillYourDetails.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 16));
    lblFillYourDetails.setBounds(409, 36, 164, 31);
    contentPanel.add(lblFillYourDetails);

    JLabel lblTravellingRequired = new JLabel("Travelling Required :");
    lblTravellingRequired.setBounds(47, 111, 123, 14);
    contentPanel.add(lblTravellingRequired);

    String[] travelling={"Yes","No"};
    final JComboBox travellingCombo = new JComboBox(travelling);
    travellingCombo.addItemListener(new ItemListener() {
        public void itemStateChanged(ItemEvent e) {
            String Travellingchoice=(String) travellingCombo.getSelectedItem();
            if(Travellingchoice.equals("Yes"))
            {                   
                from.setEditable(true);
                to.setEditable(true);
                distance.setEditable(true);             
            }
            else if(Travellingchoice.equals("No"))
            {                   
                from.setEditable(false);    
                to.setEditable(false);
                distance.setEditable(false);
            }
        }
    });
    travellingCombo.setBounds(174, 108, 66, 20);
    contentPanel.add(travellingCombo);

    JLabel lblFrom = new JLabel("From");
    lblFrom.setBounds(298, 111, 34, 14);
    contentPanel.add(lblFrom);

    from = new JTextField();
    from.setBounds(331, 108, 101, 20);
    contentPanel.add(from);
    from.setColumns(10);

    JLabel lblTo = new JLabel("To");
    lblTo.setBounds(472, 111, 34, 14);
    contentPanel.add(lblTo);

    to = new JTextField();
    to.setBounds(499, 108, 101, 20);
    contentPanel.add(to);
    to.setColumns(10);

    JLabel lblTotalEstimatedDistance = new JLabel("Total Estimated Distance");
    lblTotalEstimatedDistance.setBounds(626, 111, 143, 14);
    contentPanel.add(lblTotalEstimatedDistance);

    distance = new JTextField();        
    distance.setBounds(779, 108, 86, 20);
    contentPanel.add(distance);
    distance.setColumns(10);

    JLabel lblKilometers = new JLabel("Kilometers");
    lblKilometers.setBounds(875, 111, 75, 14);
    contentPanel.add(lblKilometers);

    JLabel lblTotalEstimatedCost = new JLabel("Total Estimated Cost");
    lblTotalEstimatedCost.setBounds(626, 166, 141, 14);
    contentPanel.add(lblTotalEstimatedCost);

    totalcost = new JTextField();
    totalcost.setBounds(779, 163, 86, 20);
    contentPanel.add(totalcost);
    totalcost.setColumns(10);

    JButton btnCalculateTravellingExpense = new JButton("Calculate Travelling Expense");
    btnCalculateTravellingExpense.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
         int cal=Integer.parseInt(distance.getText());
         double cost=cal*1.50;
         String total=String.valueOf(cost);
         totalcost.setText(total);
        }
    });
    btnCalculateTravellingExpense.setBounds(329, 162, 201, 23);
    contentPanel.add(btnCalculateTravellingExpense);

    JLabel lblRupees = new JLabel("Rupees");
    lblRupees.setBounds(875, 166, 46, 14);
    contentPanel.add(lblRupees);
    {
        JPanel buttonPane = new JPanel();
        buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
        getContentPane().add(buttonPane, BorderLayout.SOUTH);
    }
}
}

Answer 1

当您使用ItemListener时，您需要验证下一个事件状态：

    JComboBox<String> box = new JComboBox<>();
    box.addItemListener(new ItemListener() {

        @Override
        public void itemStateChanged(ItemEvent e) {
            if(e.getStateChange() == ItemEvent.SELECTED){
                // do something
            }
        }
    });

在tutorial中阅读更多内容。