从另一个 JFrame 获取变量信息时遇到问题 [英] trouble obtaining variable info from another JFrame

问题描述

I am trying to create something similar to a JOptionPane but will obtain more than one(3) variables from input. So I figured I would use a separate JFrame that had three textFields. I used access methods like Get and Set to get the variables from one class to another, but I am getting a null pointer excpetion. I figure I am going about getting the variables the wrong way, and am having a hard time trying to find a viable solution.

public class Instructor()
{
public void Insert(JPanel panel)
{
panel.removeAll();
panel.updateUI();
//ResultSet resultSet = null;
    String bNum = "";
String fName = "";  
String lName = "";


    InsertFrame insert = new InsertFrame();
    insert.setVisible(true);
    bNum = insert.getBNumber();
fName = insert.getFirstName();  
lName = insert.getLastName();

    /*
    String bNum = JOptionPane.showInputDialog("Enter BNumber");
    String fName = JOptionPane.showInputDialog("Enter First Name");
    String lName = JOptionPane.showInputDialog("Enter Last Name");*/
try
{
    connection = DriverManager.getConnection(URL);
    insertNewInstructor = connection.prepareStatement(
    "INSERT INTO Instructor" + "(BNumber, FirstName, LastName)" + "VALUES           (?,?,?)");
}catch(SQLException sqlException){
    sqlException.printStackTrace();
    System.exit(1);
}//end catch


try
{
    insertNewInstructor.setString(1, bNum);
    insertNewInstructor.setString(2, fName);
    insertNewInstructor.setString(3, lName);
    insertNewInstructor.executeUpdate();
}catch(SQLException sqlException){
        sqlException.printStackTrace();
}//end of catch
finally
{
    close();
}//end 

Display(panel);

 }//end of insert method
 }//end of class Instructor

class InsertFrame extends JFrame implements ActionListener
{

private JTextField bNumber;
private JLabel bNum;
private JTextField firstName;
private JLabel fName;
private JTextField lastName;
private JLabel lName;
private JButton ok;
private JPanel fieldPanel;
    private JPanel buttonPanel;
    private String bNumr = "";
    private String frName = "";
    private String lsName = "";

public InsertFrame()
{
bNumber = new JTextField(10);
bNum = new JLabel();
firstName = new JTextField(10);
fName = new JLabel();
lastName = new JTextField(10);
lName = new JLabel();

fieldPanel = new JPanel();
fieldPanel.setLayout(new GridLayout(3,2,4,4));
bNum.setText("B-Number:");
fieldPanel.add(bNum);
fieldPanel.add(bNumber);
fName.setText("First Name:");
fieldPanel.add(fName);
fieldPanel.add(firstName);
lName.setText("Last Name:");
fieldPanel.add(lName);
fieldPanel.add(lastName);
    ok = new JButton("Ok");
    ok.addActionListener(this);

this.add(fieldPanel, BorderLayout.CENTER);
this.add(buttonPanel,BorderLayout.SOUTH);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(310,300);
this.setResizable(false);
this.setVisible(false);
}//end of constructor
public void actionPerformed(ActionEvent e)
{
bNumr = bNumber.getText();
frName = firstName.getText();
lsName = lastName.getText();
}//end of method actionPerformed

public void setBNumber(String number)
{
bNumr = number;
}//end of setBNumber
public String getBNumber()
{
return bNumr;
}//end of getBNumber method
public void setFirstName(String firstN)
{
frName = firstN;
}//end of setFirstName
public String getFirstName()
{
return frName;
}//end of getFirstName method
public void setLastName(String lastN)
{
lsName = lastN;
}//end of setLastName method
public String getLastName()
{
return lsName;
}//end of getLastName method
}//end of InsertFrame

解决方案

Again, why not use a JOptionPane? Many people misunderstand these useful constructs, thinking that they can only be used for the most simple gui's when nothing could be further from the truth. The key in using these for maximal power is to understand that the second parameter in most JOptionPane methods is Object, and that this Object can be a very complex and even a large JPanel that holds other components including other JPanels, JTables, JComboBoxes, etc... I've used this to present complex modal input dialogs to the user, much like what you're trying to do. Then when the JOptionPane has been dealt with and program flow returns to your program, you query the properties of the complex GUI that was displayed in the JOptionPane and extract its information. Again, please check out my link here, to see exactly what I mean.

For instance, for your situation, if you wanted a JPanel that held 3 JTextFields to get your b-number, first Name, and last name information, simply create a JPanel that holds the JTextFields and their corresponding JLabels:

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.util.HashMap;
import java.util.Map;

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

class PlayerEditorPanel extends JPanel {
   enum FieldTitle {
      B_NUMBER("B Number"), FIRST_NAME("First Name"), LAST_NAME("Last Name");
      private String title;

      private FieldTitle(String title) {
         this.title = title;
      }

      public String getTitle() {
         return title;
      }
   };

   private static final Insets WEST_INSETS = new Insets(5, 0, 5, 5);
   private static final Insets EAST_INSETS = new Insets(5, 5, 5, 0);
   private Map<FieldTitle, JTextField> fieldMap = new HashMap<FieldTitle, JTextField>();

   public PlayerEditorPanel() {
      setLayout(new GridBagLayout());
      setBorder(BorderFactory.createCompoundBorder(
            BorderFactory.createTitledBorder("Player Editor"),
            BorderFactory.createEmptyBorder(5, 5, 5, 5)));
      GridBagConstraints gbc;
      for (int i = 0; i < FieldTitle.values().length; i++) {
         FieldTitle fieldTitle = FieldTitle.values()[i];
         gbc = createGbc(0, i);
         add(new JLabel(fieldTitle.getTitle() + ":", JLabel.LEFT), gbc);
         gbc = createGbc(1, i);
         JTextField textField = new JTextField(10);
         add(textField, gbc);

         fieldMap.put(fieldTitle, textField);
      }
   }

   private GridBagConstraints createGbc(int x, int y) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = x;
      gbc.gridy = y;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;

      gbc.anchor = (x == 0) ? GridBagConstraints.WEST : GridBagConstraints.EAST;
      gbc.fill = (x == 0) ? GridBagConstraints.BOTH
            : GridBagConstraints.HORIZONTAL;

      gbc.insets = (x == 0) ? WEST_INSETS : EAST_INSETS;
      gbc.weightx = (x == 0) ? 0.1 : 1.0;
      gbc.weighty = 1.0;
      return gbc;
   }

   public String getFieldText(FieldTitle fieldTitle) {
      return fieldMap.get(fieldTitle).getText();
   }

}

Then show it in a JOptionPane like so:

PlayerEditorPanel playerEditorPanel = new PlayerEditorPanel();


int result = JOptionPane.showConfirmDialog(null, playerEditorPanel,
    "Edit Player JOptionPane", JOptionPane.OK_CANCEL_OPTION,
    JOptionPane.PLAIN_MESSAGE);

and then extract the necessary information from the JPanel:

        if (result == JOptionPane.OK_OPTION) {
           for (PlayerEditorPanel.FieldTitle fieldTitle : PlayerEditorPanel.FieldTitle
                 .values()) {
              textArea.append(String.format("%10s: %s%n",
                    fieldTitle.getTitle(),
                    playerEditorPanel.getFieldText(fieldTitle)));
           }
        }

The main class could look like:

import java.awt.*;
import java.awt.event.*;
import java.util.HashMap;
import java.util.Map;

import javax.swing.*;

@SuppressWarnings("serial")
public class ComplexOptionPane extends JPanel {
   private PlayerEditorPanel playerEditorPanel = new PlayerEditorPanel();
   private JTextArea textArea = new JTextArea(12, 30);

   public ComplexOptionPane() {
      textArea.setEditable(false);
      textArea.setFocusable(false);
      textArea.setFont(new Font(Font.MONOSPACED, Font.PLAIN, 16));
      JPanel bottomPanel = new JPanel();
      bottomPanel.add(new JButton(new AbstractAction("Get Player Information") {

         @Override
         public void actionPerformed(ActionEvent arg0) {
            int result = JOptionPane.showConfirmDialog(null, playerEditorPanel,
                  "Edit Player JOptionPane", JOptionPane.OK_CANCEL_OPTION,
                  JOptionPane.PLAIN_MESSAGE);
            if (result == JOptionPane.OK_OPTION) {
               for (PlayerEditorPanel.FieldTitle fieldTitle : PlayerEditorPanel.FieldTitle
                     .values()) {
                  textArea.append(String.format("%10s: %s%n",
                        fieldTitle.getTitle(),
                        playerEditorPanel.getFieldText(fieldTitle)));
               }
            }
         }
      }));
      setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
      setLayout(new BorderLayout(5, 5));
      add(new JScrollPane(textArea), BorderLayout.CENTER);
      add(bottomPanel, BorderLayout.PAGE_END);
   }

   private static void createAndShowGui() {
      ComplexOptionPane mainPanel = new ComplexOptionPane();

      JFrame frame = new JFrame("ComplexOptionPane");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

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