无法从另一个JFrame获取变量信息
我正在尝试创建类似于JOptionPane的东西，但是会从输入中获得多个（3）个变量。 所以我想我会使用一个单独的JFrame，它有三个textFields。 我使用Get和Set等访问方法将变量从一个类获取到另一个类，但我得到一个空指针excpetion。 我想我会以错误的方式获取变量，并且很难找到可行的解决方案。
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 再次，为什么不使用JOptionPane？ 许多人误解了这些有用的结构，认为它们只能用于最简单的gui，当没有任何东西可以离真相更远时。 使用它们获得最大功率的关键是要理解大多数JOptionPane方法中的第二个参数是Object ，并且该Object可以是一个非常复杂的甚至是一个大型JPanel，它包含其他组件，包括其他JPanel，JTable，JComboBox等。 ..我用它来向用户呈现复杂的模态输入对话框，就像你想要做的那样。 然后，当处理了JOptionPane并且程序流返回到您的程序时，您将查询JOptionPane中显示的复杂GUI的属性并提取其信息。 再次，请在这里查看我的链接，看看我的意思。
例如，对于您的情况，如果您想要一个包含3个JTextField的JPanel来获取您的b-number，名字和姓氏信息，只需创建一个包含JTextField及其相应JLabel的JPanel：
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 fieldMap = new HashMap(); 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(); } }
然后在JOptionPane中显示它，如下所示：
PlayerEditorPanel playerEditorPanel = new PlayerEditorPanel(); int result = JOptionPane.showConfirmDialog(null, playerEditorPanel, "Edit Player JOptionPane", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
然后从JPanel中提取必要的信息：
if (result == JOptionPane.OK_OPTION) { for (PlayerEditorPanel.FieldTitle fieldTitle : PlayerEditorPanel.FieldTitle .values()) { textArea.append(String.format("%10s: %s%n", fieldTitle.getTitle(), playerEditorPanel.getFieldText(fieldTitle))); } }
主要类看起来像：
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(); } }); } }