我试图通过使用RowSorter的文本字段中的内容过滤JTable1。当我在字段中输入文本时，我收到这个错误消息:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javaapplication2.NewJFrame.newFilter(NewJFrame.java:221)
at javaapplication2.NewJFrame.access$000(NewJFrame.java:28)
at javaapplication2.NewJFrame$1.insertUpdate(NewJFrame.java:88)
不确定为什么我得到一个NullPointerException。
下面是我的代码:
package javaapplication2;
import java.util.Vector;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.Timer;
import javax.swing.Icon;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import org.jdesktop.beansbinding.AbstractBindingListener;
import org.jdesktop.beansbinding.Binding;
import org.jdesktop.beansbinding.PropertyStateEvent;
import javax.swing.*;
import javax.swing.table.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
public class NewJFrame extends javax.swing.JFrame {
private Vector<Vector<String>> data; //used for data from database
private Vector<String> header; //used to store data header
private Vector<Vector<String>> data2; //used for data from database
private Vector<String> header2; //used to store data header
public NewJFrame() throws Exception {
DbWork newDatabase = new DbWork();
//get data from database
data = newDatabase.getEmployee();
//create header for employee table
header = new Vector<String>();
header.add("EmployeeID");
header.add("FirstName");
header.add("LastName");
header.add("MI");
header.add("HomeAddress");
header.add("State");
header.add("Zip");
header.add("DateOfBirth");
header.add("HireDate");
header.add("TerminationDate");
header.add("LicenseDate");
header.add("Active");
header.add("ManagerID");
header.add("ModifiedID");
data2 = newDatabase.getTrucks();
//create header for truck table
header2 = new Vector<String>();
header2.add("TruckID");
header2.add("VinNumber");
header2.add("Make");
header2.add("Model");
header2.add("TruckYear");
header2.add("PriceAcquired");
header2.add("LicenseNumber");
header2.add("ModifiedID");
header2.add("DriverFirstName");
header2.add("DriverLastName");
header2.add("DriverMI");
initComponents();
new TableRowSorter<TableModel>(model1);
jTable1.setRowSorter(sorter);
txtFilter.getDocument().addDocumentListener(
new DocumentListener(){
public void changedUpdate(DocumentEvent e){
newFilter();
}
public void insertUpdate(DocumentEvent e){
newFilter();
}
public void removeUpdate(DocumentEvent e){
newFilter();
}
}
);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jTabbedPane1 = new javax.swing.JTabbedPane();
jScrollPane1 = new javax.swing.JScrollPane();
jTable1 = new javax.swing.JTable(model1);
jScrollPane2 = new javax.swing.JScrollPane();
jTable2 = new javax.swing.JTable();
jLabel1 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
jButton2 = new javax.swing.JButton();
txtFilter = new javax.swing.JTextField();
jMenuBar1 = new javax.swing.JMenuBar();
jMenu1 = new javax.swing.JMenu();
jMenu2 = new javax.swing.JMenu();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Tracking System - Prototype");
jTable1.setModel(new javax.swing.table.DefaultTableModel(
data, header
));
jTable1.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
jScrollPane1.setViewportView(jTable1);
jTabbedPane1.addTab("Employees", jScrollPane1);
jTable2.setModel(new javax.swing.table.DefaultTableModel(
data2, header2
));
jTable2.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
jScrollPane2.setViewportView(jTable2);
jTabbedPane1.addTab("Trucks", jScrollPane2);
jButton1.setText("Modify Record");
jButton2.setText("New Record");
jMenu1.setText("File");
jMenuBar1.add(jMenu1);
jMenu2.setText("Edit");
jMenuBar1.add(jMenu2);
setJMenuBar(jMenuBar1);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(0, 0, Short.MAX_VALUE)
.addComponent(jLabel1)
.addGap(307, 307, 307))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jTabbedPane1)
.addContainerGap())
.addGroup(layout.createSequentialGroup()
.addComponent(jButton1)
.addGap(18, 18, 18)
.addComponent(jButton2)
.addGap(104, 104, 104)
.addComponent(txtFilter, javax.swing.GroupLayout.PREFERRED_SIZE, 187, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(0, 351, Short.MAX_VALUE))))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap()
.addComponent(jTabbedPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 349, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 18, Short.MAX_VALUE)
.addComponent(jLabel1)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jButton1)
.addComponent(jButton2)
.addComponent(txtFilter, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(62, 62, 62))
);
pack();
}// </editor-fold>
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
try
{
new NewJFrame().setVisible(true);
}catch(Exception e){e.printStackTrace();}
}
});
}
private void newFilter() {
RowFilter<TableModel, Object> rf = null;
//If current expression doesn't parse, don't update.
try {
rf = RowFilter.regexFilter(txtFilter.getText(),0);
} catch (Exception e) {
return;
}
sorter.setRowFilter(rf);
}
TableModel model1 = new DefaultTableModel();
TableRowSorter<TableModel>sorter;
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JLabel jLabel1;
private javax.swing.JMenu jMenu1;
private javax.swing.JMenu jMenu2;
private javax.swing.JMenuBar jMenuBar1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JScrollPane jScrollPane2;
private javax.swing.JTabbedPane jTabbedPane1;
private javax.swing.JTable jTable1;
private javax.swing.JTable jTable2;
private javax.swing.JTextField txtFilter;
// End of variables declaration
}
问题是分类器是…null:-)这是因为您从未设置字段:
// creates a sorter which is nowhere used
new TableRowSorter<TableModel>(model1);
// declares a field that's not initialized
TableRowSorter<TableModel> sorter;
// you have to combine both to initialize the sorter field
sorter = new TableRowSorter<TableModel>(model1);
jTable1.setRowSorter(sorter);
无论如何，没有必要手动安装rowSorter，让表为您管理它，并在需要时抓取自动创建的排序器:
// configure the table to create a rowSorter as needed
jTable1.setAutoCreateRowSorter(true);
// access the auto-created sorter in newFilter
TableRowSorter sorter = (TableRowSorter) table.getRowSorter();
sorter.setRowFilter(rf);