NullPointerException JFrame

Hi guys,
I am getting this error:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
     at com.ankix.snapxplorer.gui.pane.explorer.events.MenuBarActionListenerImpl$1.run(MenuBarActionListenerImpl.java:134)
     at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
     at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
     at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)While on this:
public class MenuBarActionListenerImpl implements ActionListener
     //               CLASS MEMBERS
     private Component objRef;
     private ProcessPane objProcessPane;
     private UsersPane objUsersPane;
     //            CLASS CONSTRUCTOR
     public MenuBarActionListenerImpl(Component pComponent)     //pComponent instance of JMenuBar
          this.objRef = pComponent;
     //               CLASS METHODS
     public void actionPerformed(ActionEvent e)
          if(((JMenuItem)e.getSource()).getText() == "Logout")
               this.objProcessPane = null;
               this.objUsersPane = null;
               SwingUtilities.invokeLater(new Runnable()
                    public void run()
                         ((javax.swing.JFrame)objRef.getParent().getParent().getParent().getParent()).setContentPane(new LoginPane((javax.swing.JFrame)objRef.getParent().getParent().getParent().getParent()));
                         ((javax.swing.JFrame)objRef.getParent().getParent().getParent().getParent()).validate();
                         ((javax.swing.JFrame)objRef.getParent().getParent().getParent().getParent()).repaint();
}I know "objRef.getParent().getParent().getParent().getParent()" is the instance of the JFrame I am looking for so I can't figure out wthe problem.
Any ideas why this is happening?
Many Thanks,
MeTitus

Aehm, it might be easier to track down your problem by rewriting that actionPerformed:public void actionPerformed( ActionEvent e )
    if ("Logout".equals(((JMenuItem)e.getSource()).getText()))
        this.objProcessPane = null;
        this.objUsersPane = null;
        final Window w = SwingUtilities.getWindowAncestor(objRef);
        if (w instanceof JFrame)
            final JFrame frame = (JFrame)w;
            frame.setContentPane(new LoginPane(frame));
            frame.validate();
            frame.repaint();
}Less method invocations per line narrow down the possibilities for NPEs!
BTW - do not use == to compare Strings!

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MissLynda wrote:
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Some possibly helpful suggestions:
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Please run my coding first, and get some view from my coding.
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//switches to contain Strings. Starting with v 1.3,
//the table automatically converts value to an Integer,
//so you only need the code in the 'else' part of this
//'if' block.
try {
data[row][col] = new Integer(value.toString());
fireTableCellUpdated(row, col);
} catch (NumberFormatException e) {
JOptionPane.showMessageDialog(TableRenderDemo.this,
"The \"" + getColumnName(col)
+ "\" column accepts only integer values.");
} else {
data[row][col] = value;
fireTableCellUpdated(row, col);
if (DEBUG) {
System.out.println("New value of data:");
printDebugData();
private void printDebugData() {
int numRows = getRowCount();
int numCols = getColumnCount();
for (int i=0; i < numRows; i++) {
System.out.print(" row " + i + ":");
for (int j=0; j < numCols; j++) {
System.out.print(" " + data[i][j]);
System.out.println();
System.out.println("--------------------------");

http://forum.java.sun.com/faq.jsp#format

JApplet with JFrame fails to load in browser

I have been making a Java program that runs a JApplet the program operates perfectly in NetBeans (the Java development kit), but when I run it in the browser, it fails to load.
The code is...
import java.awt.*;
import javax.swing.*;
public class CalculatorMain extends javax.swing.JApplet {
private Difficulty difficulty = new Difficulty();
private Troop[] troop = new Troop[7];
private Army army = new Army(troop);
private Calculator calculator = new Calculator(difficulty, army);
private CalculatorListener listener;
public void init(){
JPanel supreme = new JPanel();
supreme.setLayout(new BorderLayout());
for (byte i = 0; i < 7; i++) {troop[i] = new Troop();}
DifficultyPanel diffpanel = new DifficultyPanel(difficulty);
ArmyPanel armypanel = new ArmyPanel(troop);
JButton calbut = new JButton("Calculate Experience");
JLabel xpDisplay = new JLabel(" ");
CalculatorPanel calpanel = new CalculatorPanel(calculator, calbut, xpDisplay);
JFrame frame = new JFrame();
listener = new CalculatorListener(xpDisplay, calculator, diffpanel, armypanel, calpanel);
calbut.addActionListener(listener);
supreme.add(diffpanel, BorderLayout.WEST);
supreme.add(armypanel, BorderLayout.CENTER);
supreme.add(calpanel, BorderLayout.SOUTH);
frame.add(supreme);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
As I said, it does not work in the web browser (which is Internet Explorer 6.0). In the information window I open, the message is...
Java Plug-in 1.5.0_06
Anv�nder JRE-version 1.5.0_06 Java HotSpot(TM) Client VM
java.security.AccessControlException: access denied (java.lang.RuntimePermission exitVM)
     at java.security.AccessControlContext.checkPermission(Unknown Source)
     at java.security.AccessController.checkPermission(Unknown Source)
     at java.lang.SecurityManager.checkPermission(Unknown Source)
     at java.lang.SecurityManager.checkExit(Unknown Source)
     at javax.swing.JFrame.setDefaultCloseOperation(Unknown Source)
     at CalculatorMain.init(CalculatorMain.java:31)
     at sun.applet.AppletPanel.run(Unknown Source)
     at java.lang.Thread.run(Unknown Source)
Exception in thread "thread applet-CalculatorMain.class" java.lang.NullPointerException
     at sun.plugin.util.GrayBoxPainter.showLoadingError(Unknown Source)
     at sun.plugin.AppletViewer.showAppletException(Unknown Source)
     at sun.applet.AppletPanel.run(Unknown Source)
     at java.lang.Thread.run(Unknown Source)
Any idea what might be wrong?

If you look at your error message you'll see...
java.security.AccessControlException: access deniedAh. Problem # 1 caused at
     at CalculatorMain.init(CalculatorMain.java:31)Problem #2
java.lang.NullPointerExceptionat
     at sun.applet.AppletPanel.run(Unknown Source)
     at java.lang.Thread.run(Unknown Source)So it says it can't display the init error message. That's ok this should go away when you fix bug #1

Multiple Components in a JFrame (simple question)

Hello everyone, I need to put two components in my JFrame, and I have been expieriencing some odd problems. I use this to add my components...
MyComponent mc=new MyComponent();
MyOtherComponent me = new MyOtherComponent();
When I try to access methods they work fine. I can use repaint() in a method and it works. BUT when I try to draw on the component using anything besides paintComponent() It gives me a java.lang.NullPointerException
here is what I tried.....
me.draw(getGraphics());
//later on in the component def..
draw(Graphics g) {
} // I get a java.lang.NullPointerException in main
whenever i use getGraphics() it does'nt work what am I doing wrong?

Yup I did that and repaint does jack all. When I run the code all I see the contents of the first component. I know that the methods of the second component are being executed, but the paintComponent method is simply not running. I put a System.out.println("hi"); in and it never showed in the console..
Anyone who can help me gets a duke, here's my second component code..
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
class MyOtherComponent extends JComponent {
public void paintComponent(Graphics gg) {
System.out.println("paintComponent executed!!!");
Graphics2D g2D = (Graphics2D)gg;
ImageIcon icon = null;
try {icon = new ImageIcon(new URL("http://images.neopets.com/m.gif")); }
catch(MalformedURLException e) {
System.out.println("no"); return;
resize(icon.getIconWidth(),icon.getIconHeight());
Image mark = icon.getImage();
g2D.drawImage(mark,0,0,this);
g2D.drawString("hello folk",40,40);
drawe(g2D);
public void drawe(Graphics2D g2D) {
g2D.drawLine(50,50,500,500);
g2D.fillRect(20,20,20,20);
repaint();
public void line() {
System.out.println("Hello, from MyOtherComponent");
public void re() {
repaint();
System.out.println("re");
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To use a static variable in another class,but report NullPointerException

when TableMain is running,I run testRecord so that let TableMain add a occur informatin and
happened time in a row in TableMain,but when I run testRecord,java report a NullPointerException and I dont know how to solve this problem,thanks for helping me to check my code;(error report info is in end)
import java.awt.event.*;
import javax.swing.table.*;
import java.io.*;
public class TableMain extends JFrame{
JTable table;
static OwnModel model;
String[] columnHeader={"occur","time"};
class OwnModel extends DefaultTableModel{
public OwnModel(Object[] columnNames,int numRows){
super(columnNames,numRows);
public boolean isCellEditable(int row,int column){
return false;
public TableMain(){
model=new OwnModel(columnHeader,0);
table=new JTable(model);
JScrollPane scroll=new JScrollPane(table);
JButton save=new JButton("save record");
JButton delete=new JButton("delete record");
JPanel buttons=new JPanel();
buttons.add(save);
buttons.add(delete);
JLabel sign=new JLabel("occur record");
Container cp=getContentPane();
cp.add(BorderLayout.NORTH,sign);
cp.add(BorderLayout.CENTER,scroll);
cp.add(BorderLayout.SOUTH,buttons);
this.setSize(300,500);
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
public static void main(String[] args){
new TableMain();
import java.util.Vector;
import java.util.Calendar;
import java.text.SimpleDateFormat;
public class testRecord{
public static void main(String[] args){
SimpleDateFormat simpledf=new SimpleDateFormat("yyyy/MM/dd hh:mm:ss");
String tableName="friends";
Calendar occurtime=Calendar.getInstance();
Vector record=new Vector();
record.add("send 'desc' sql, "+"operated table is :"+tableName);
record.add(simpledf.format(occurtime.getTime()));
System.out.println("model is "+Guide.model);
System.out.println("record is "+record);
Guide.model.addRow(record);
error report:
model is null
record is [send 'desc' sql,operated table is :friends, 2004/05/26 11:39:03]
Exception in thread "main" java.lang.NullPointerException
at testRecord.main(testRecord.java:14)

but I just use this constructor once,never use twice
with same jvm;I thinks my idea is not too very badIt's a public constructor (if I'm looking in the right
place) - it could be called from anywhere. To
intialize a static variable outside the declaration,
use a static initializer:private static String whatever;static {
whatever = "whatever";
}Or simply (in this case):private static String whatever = "whatever";

Java.lang.NullPointerException javax.xml.parsers.DocumentBuilder.parse

Hi all,
i have a problem by solving an error in my code. The Code is mainly from Ian Darwin.
The code i am running works with j2sdk1.4.2_04. But now i have to bring it to work with jdk1.6.0_13.
The code parses xml documents. With small xml documents the code works. With large xml documents i get the following error while running the produced class file.
Exception in thread "main" java.lang.NullPointerException
at com.sun.org.apache.xerces.internal.dom.DeferredDocumentImpl.setChunkIndex(DeferredDocumentImpl.java:1944)
at com.sun.org.apache.xerces.internal.dom.DeferredDocumentImpl.appendChild(DeferredDocumentImpl.java:644)
at com.sun.org.apache.xerces.internal.parsers.AbstractDOMParser.characters(AbstractDOMParser.java:1191)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.characters(XMLDTDValidator.java:862)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:463)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:225)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:283)
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:208)
at XParse.parse(XParse.java:38)
at XParse$JFileChooserrv.<init>(XParse.java:119)
at XParse.main(XParse.java:213)
I know what a java.lang.NullPointerException mens. But i don't know where i have to look for. Specially i don't know what or where "com.sun.org.apache...." is.
Is there a package that a have to add to the environment? Can some one tell my where i can find this package?
I wrote the code for some years ago, 2006 or so. With the knew jdk1.6.0_13 some thinks chance in the environment. Couldn't find what exactly.
The code has only 215 lines, but some how i can't add it to this Message, because Maximum allowed is only 7500.
Is there an other Forum, which may is better for my question?

Here is the code:
import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.xml.sax.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
import java.awt.Container;
import javax.swing.JTextArea;
* This code is mainly from @author Ian Darwin, [email protected]
public class XParse {
     /** Convert the file */
     public static void parse(File file, boolean validate) {
          try {
               System.err.println("");
               String fileName = file.getAbsolutePath();
               System.err.println("Parsing " + fileName + "...");
               // Make the document a URL so relative DTD works.
               //String uri = new File(fileName).getAbsolutePath();
               //System.err.println(uri);
               DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
               if (validate)
               f.setValidating(true);
               DocumentBuilder p = f.newDocumentBuilder();
               p.setErrorHandler(new MyErrorHandler(System.err));
               //XmlDocument doc = XmlDocument.createXMLDocument(file);
               boolean vaild = p.isValidating();
               if (vaild) {
                    System.out.println("yes parsing");
                    Document doc = p.parse(file); // <<<< ERROR
               System.out.println("Parsed OK");
          } catch (SAXParseException ex) {
               System.err.println("+================================+");
               System.err.println("|       *SAX Parse Error*        |");
               System.err.println("+================================+");
               System.err.println(ex.toString());
               System.err.println("At line " + ex.getLineNumber());
               System.err.println("+================================+");
          } /**catch (RuntimeException ex) {
               System.err.println("+================================+");
               System.err.println("|       *SAX Parse Error*        |");
               System.err.println("+================================+");
               System.err.println(ex.toString());
               //System.err.println("At line " + ex.getLineNumber());
               //System.err.println("At line " + ex.getMessage());
               System.err.println("+================================+");
          }**/ catch (SAXException ex) {
               System.err.println("+================================+");
               System.err.println("|          *SAX Error*           |");
               System.err.println("+================================+");
               System.err.println(ex.toString());
               System.err.println("+================================+");
          /*}} catch (SAXNotRecognizedException ex) {
               System.err.println(" no SAX");*/
          } catch (ParserConfigurationException ex) {
               System.err.println(" ???");
           } catch (IOException ex) {
               System.err.println("+================================+");
               System.err.println("|           *XML Error*          |");
               System.err.println("+================================+");
               System.err.println(ex.toString());
private static class JFileChooserrv {
     JFileChooserrv(JFrame f, boolean vverabreiten) {
          String openfile;
          String verror;
          boolean validate = true;
          final JFrame frame = f;
          String vFilename = "Z:\\Boorberg\\parsen_vista\\daten";
          //String vFilename = "C:\\";
          File vFile = new File(vFilename);
          final JFileChooser chooser = new JFileChooser(vFile);
          JFileFilter filter = new JFileFilter();
          filter.addType("xml");
          filter.addType("sgml");
          filter.addType("html");
          filter.addType("java");
          filter.setDescription("strukturfiles");
          chooser.addChoosableFileFilter(filter);
          boolean vjeas = true;
          chooser.setMultiSelectionEnabled(vjeas);
          int returnVal = chooser.showOpenDialog(frame);
          if (returnVal == JFileChooser.APPROVE_OPTION) {
               //Array filearry[] = chooser.getSelectedFiles();
               //if (vFile = chooser.getSelectedFiles()) {
               //File file[] = chooser.getSelectedFiles();
               File vfile[] = chooser.getSelectedFiles();
               //String openfile = new String();
               int vlenght = vfile.length;
               if (vlenght>1) {
                    int x=0;
                    while (x< vlenght) {
                              parse(vfile[x], validate);
                              x = x +1;
               if (vlenght<=1) {
                    File v2file = chooser.getSelectedFile();
                         parse(v2file, validate);
          } else {
               System.out.println("You did not choose a filesystem           object.");
     System.exit(0);
private static class JFileFilter extends javax.swing.filechooser.FileFilter {
     protected String description, vnew;
     protected ArrayList<String> exts = new ArrayList<String>();
     protected boolean vtrue;
     public void addType(String s) {
          exts.add(s);
     /** Return true if the given file is accepted by this filter. */
     public boolean accept(File f) {
          // Little trick: if you don't do this, only directory names
          // ending in one of the extentions appear in the window.
          if (f.isDirectory()) {
               return true;
          } else if (f.isFile()) {
               Iterator it = exts.iterator();
               while (it.hasNext()) {
                    if (f.getName().endsWith((String)it.next()))
                         return true;
          // A file that didn't match, or a weirdo (e.g. UNIX device file?).
          return false;
     /** Set the printable description of this filter. */
     public void setDescription(String s) {
          description = s;
     /** Return the printable description of this filter. */
     public String getDescription() {
          return description;
private static class MyErrorHandler implements ErrorHandler {
        // Error handler output goes here
        private PrintStream out;
        MyErrorHandler(PrintStream out) {
            this.out = out;
         * Returns a string describing parse exception details
        private String getParseExceptionInfo(SAXParseException spe) {
            String systemId = spe.getSystemId();
            if (systemId == null) {
                systemId = "null";
            String info = "URI=" + systemId +
                " Line=" + spe.getLineNumber() +
                ": " + spe.getMessage();
            return info;
        // The following methods are standard SAX ErrorHandler methods.
        // See SAX documentation for more info.
        public void warning(SAXParseException spe) throws SAXException {
               //System.exit(0);
            //out.println("Warning: " + getParseExceptionInfo(spe));
        public void error(SAXParseException spe) throws SAXException {
               //System.exit(0);
            String message = "Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
        public void fatalError(SAXParseException spe) throws SAXException {
               //System.exit(0);
            String message = "Fatal Error: " + getParseExceptionInfo(spe);
            throw new SAXException(message);
     public static void main(String[] av) {
          JFrame vframe = new JFrame("chose files to pars");
          boolean vverabreiten = true;
          boolean validate = true;
          JFileChooserrv vdateienwaehlen = new JFileChooserrv(vframe, vverabreiten);
}The Stack Trace i posted in the last Message. But i couldn't read it, i am not a programmer.

Problem about "Exception in thread "main" java.lang.NullPointerException"

This is t error message once i run the file
Exception in thread "main" java.lang.NullPointerException
at sendInterface.<init>(sendInterface.java:64)
at sendInterface.main(sendInterface.java:133)
* @(#)sendInterface.java
* @author
* @version 1.00 2008/7/18
import java.awt.BorderLayout;
import java.awt.Image;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultListModel;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.ListModel;
import javax.swing.UIManager;
import javax.swing.SwingConstants;
import java.io.*;
import java.sql.*;
import java.net.*;
public class sendInterface /*implements ActionListener*/{
     JFrame frame = new JFrame();
     private Panel topPanel;
     private Panel sendMessagePanel;
     private Panel sendFilePanel;
     private JLabel senderID;
     private JLabel receiverID;
     private JLabel senderDisplay;
     private DefaultListModel receiverListModel = new DefaultListModel();
     private JList receiverID_lst = new JList(receiverListModel);
     private JRadioButton sendType;
     String userName;
     String[] userList = null ;
     int i=0;
     Connection con;
    public sendInterface() {
         String ListName;
             try
               JFrame.setDefaultLookAndFeelDecorated( true );
          catch (Exception e)
           System.err.println( "Look and feel not set." );
       frame.setTitle( "Send Interface" );
         topPanel.setLayout( new GridLayout( 2 , 1 ) );                          //line 64*************************
         senderID = new JLabel( "Sender:", SwingConstants.LEFT );
         senderDisplay = new JLabel( "'+...+'", SwingConstants.LEFT );
         receiverID = new JLabel( "Receiver:", SwingConstants.LEFT);
//         receiverID_lst = new JList( ListName );
          frame.add(senderID);
         frame.add(senderDisplay);
         frame.add(receiverID);
//         frame.add(receiverListModel);
         frame.add(new JScrollPane(receiverID_lst), BorderLayout.CENTER);
         frame.setLocation(200, 200);
         frame.setSize(250, 90);
         frame.setVisible(true);
    public void setListName(String user)
         try{
              userName = user;
              Class.forName("com.mysql.jdbc.Driver");
               String url = "jdbc:mysql://localhost:3306/thesis";
               con = DriverManager.getConnection(url, "root", "");
               Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
               ResultSet rs = stmt.executeQuery("select * from user where User_ID!= '" + userName + "'");
               System.out.println("Display all results:");
               while(rs.next()){
                  String user_id = rs.getString("User_ID");
                  System.out.println("\tuser_id= " + user_id );
     //             receiverListModel.addElement(user_id);
                    userList=user_id;
                    i++;
          }//end while loop
          receiverListModel.addElement(userList);
     catch(Exception ex)
ex.printStackTrace();
     finally
if (con != null)
try
con.close ();
System.out.println ("Database connection terminated");
catch (Exception e) { /* ignore close errors */ }
public String getUserName()
     return userName;
public String[] getUserList()
     return userList;
public static void main(String[] args) {
new sendInterface(); //line 133******************************************
thank ur reply:D
Edited by: ocibala on Aug 3, 2008 9:54 AM

And where do you instantiate topPanel before you invoke setLayout?
db

Java.lang.NullPointerException when writing to a textfield..help please?

Hi guys,
I'm getting a java.lang.NullPointerException (with no other details of error) when i try to write to a textfield on my GUI. the line: TF1.setText("F"); is where the problem is occurring. that line is within a loop ->
               if(freq >87 && freq < 100)
                                   System.out.println("Note =F" +freq);
                                   TF1.setText("F");
the textfield has been constructed and initialised and given an initial value. what i need to happen is the string in the textfield to be constantly updated (overwritten) with the new string.
the initial value from      TextField TF1= new TextField("", 10);
TF1.setText("blank");
works fine, but one the loop above is entered, the current frequency is printed to the command line and then "java.lang.NullPointerException" is thrown.
I'm struggling with this, and have a deadline to meet so I would much appreciate some help.

The Gui class is this:
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.TextField;
import javax.swing.JFrame;
import javax.swing.*;
public class Gui extends JFrame{
public static void main(String args[])
Project project = new Project();
project.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
     project.setSize( 250, 200 ); // set frame size
project.setVisible( true ); // display frame
// new Project(){//constructor
     Panel p, p1;
p = new Panel();
          p.setLayout (new FlowLayout(FlowLayout.LEFT,5,5));
          project.add(p, BorderLayout.NORTH);
     p1 = new Panel();
     p1.setLayout (new FlowLayout(FlowLayout.LEFT,5,5));
p1.setLayout (new GridLayout(4,1));
project.setTitle("Guitar Tuner Prototype");
     TextField TF1= new TextField("", 10);
TF1.setText("blank");
     p1.add(TF1);
     TF1.setVisible(true);
     p1.setVisible(true);
     p.add(p1);
//Capture input data from the microphone
project.captureAudio();
project.captureThread();
}//end constructor
//end main
The project.java class has the "private TextField TF1; at the top. the project.java class also contains the loop thats writing to the texfield as specified in th original post..

Java.lang.NullPointerException when scrolling in JComboBox

Hi everybody,
I use a JComboBox in my application. If I scroll it a NullPointerException is thrown:
java.lang.NullPointerException
     at javax.swing.BufferStrategyPaintManager.flushAccumulatedRegion(BufferStrategyPaintManager.java:406)
     at javax.swing.BufferStrategyPaintManager.copyArea(BufferStrategyPaintManager.java:334)
     at javax.swing.RepaintManager.copyArea(RepaintManager.java:1143)
     at javax.swing.JViewport.blitDoubleBuffered(JViewport.java:1604)
     at javax.swing.JViewport.windowBlitPaint(JViewport.java:1573)
     at javax.swing.JViewport.setViewPosition(JViewport.java:1118)
     at javax.swing.plaf.basic.BasicScrollPaneUI$Handler.vsbStateChanged(BasicScrollPaneUI.java:1027)
     at javax.swing.plaf.basic.BasicScrollPaneUI$Handler.stateChanged(BasicScrollPaneUI.java:1016)
     at javax.swing.DefaultBoundedRangeModel.fireStateChanged(DefaultBoundedRangeModel.java:348)
     at javax.swing.DefaultBoundedRangeModel.setRangeProperties(DefaultBoundedRangeModel.java:285)
     at javax.swing.DefaultBoundedRangeModel.setValue(DefaultBoundedRangeModel.java:151)
     at javax.swing.JScrollBar.setValue(JScrollBar.java:446)
     at javax.swing.plaf.basic.BasicScrollPaneUI$Handler.mouseWheelMoved(BasicScrollPaneUI.java:962)
     at java.awt.Component.processMouseWheelEvent(Component.java:6126)
     at java.awt.Component.processEvent(Component.java:5810)
     at java.awt.Container.processEvent(Container.java:2058)
     at java.awt.Component.dispatchEventImpl(Component.java:4410)
     at java.awt.Container.dispatchEventImpl(Container.java:2116)
     at java.awt.Component.dispatchMouseWheelToAncestor(Component.java:4555)
     at java.awt.Component.dispatchEventImpl(Component.java:4296)
     at java.awt.Container.dispatchEventImpl(Container.java:2116)
     at java.awt.Component.dispatchEvent(Component.java:4240)
     at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
     at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4015)
     at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
     at java.awt.Container.dispatchEventImpl(Container.java:2102)
     at java.awt.Window.dispatchEventImpl(Window.java:2429)
     at java.awt.Component.dispatchEvent(Component.java:4240)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
     at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
     at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)This is the code I execute:
   public static void test()
      Object[] items = new Object[10];
      items[0] = 0;
      items[1] = 1;
      items[2] = 2;
      items[3] = 3;
      items[4] = 4;
      items[5] = 5;
      items[6] = 6;
      items[7] = 7;
      items[8] = 8;
      items[9] = 9;
      JFrame frame = new JFrame("Test frame");
      JPanel panel = new JPanel();
      panel.add(new JLabel("Combobox:"));
      panel.add(new JComboBox(items));
      frame.add(panel);
      frame.pack();
      frame.setVisible(true);
   }The weird thing is that if I execute this piece of code outside my program, in a test class, everything goes fine. I am not sure how this is possible.
Best regards,
Jethro Borsje

You not assign any ActionListener to your ComboBox ?Well, in my real-life implementation I plan to do so, however in the test() method I do not. And the problem is still there in the test method, so to answer your question: no I do not add an ActionListener to the JComoBox in my test case.
A little bit more info: when I scroll in the JComboBox the scrollwheel of my mouse, the scrollbar on the right side does not move, however the contents of the JComboBox does move.

NullPointerException JFrame

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