Problems with JMenu
Hi,
i have a problem with the JMenu in a project.
The JMenu starts with a normal behaviour.
After a time an error occurs:
One JMenuitem is selected, and every move in the JMenu changes the selection only for a short time.
Then the selection jumps back to the former
selection.
Anyone who knows this problem?
Thanks
Guido
I now know when the trouble starts. When i start a DragnDrop action and then moves above the JMenu the odd behaviour starts. With the same trick this behaviour ends.
I'm now searching for a way to avoid this trouble.
The JMenu is not a Droptarget.
Any suggestions?
Guido
Similar Messages
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ActionPerformed problem with jmenu
hi i am trying to get the action performed for 'exit' in a JMenu but
i cant seem to find the problem the program will run be nothing hapens when i click exit on the menu. any help would be greatly welcomed
markimport java.awt.*;
import java.awt.event.*;
import java.sql.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;
class MyFrame2 extends JFrame implements ActionListener{
private JMenuBar bar = new JMenuBar();//create menubar
private JMenu j1 = new JMenu();
private JMenu j2 = new JMenu();
private JMenu j3 = new JMenu();
private JMenu j4 = new JMenu();
private JMenu j5 = new JMenu();
private JMenuItem jm1 = new JMenuItem();
private JMenuItem jm2 = new JMenuItem();
Container content;
public MyFrame2(String str)
{ super(str);
content= this.getContentPane();
content.setLayout(new FlowLayout());
setSize(220,250);
bar.add(j1);
bar.add(j2);
bar.add(j3);
bar.add(j4);
bar.add(j5);
j1.setText("Register");
j2.setText("Not Connected");
j3.setText("New DB");
j4.setText("Admin");
j5.setText("Exit");
j5.addActionListener(this);
jm1.setText("Server Info");
jm2.setText("User Admin");
j4.add(jm1);
j4.add(jm2);
setJMenuBar(bar);
setVisible(true); }
public void actionPerformed(ActionEvent e){
Object target=e.getSource();
if (target== j5){System.exit(0);}
public class Db4
public static void main(String args[]) {
MyFrame2 fr= new MyFrame2("Account Example");The problem is that your "j5" is a JMenu not a JMenuItem. JMenu objects respond to mouseclicks by displaying a popup menu not by calling an actionlistener. I changed "j5" to be a JMenuItem and it worked fine, although I won't advice placing JMenuItems directly on a menubar.
-
Problem with JMENU / JTEXTAREA
Hello All,
I have the following problem:
I want to create a little text editor. I just have a window containing
a menu bar and a text area. The basic functions work fine. I can open a
file and read it into the text area.
The problem I have is, that my menu is affected by the file chooser window. When I close the file chooser parts of the selected file or the
file chooser will be painted in my menu. In the worst case it deletes menu items.
Does anybody knows help?
Thank you in advance.
RalfIt sounds like your program is busy doing something else after the filechooser closes, which is causing your GUI not to repaint. I assume you are performing some io on the file after the user click the OK button, that is probably whats causing it to not redisplay your menus. Or you could be getting an exception opening your file which usually causes the GUI to hang. If you not getting an exception and your sure your io code isn't infinite looping, then your best option to fix this is to run the io code in a separate thread.
-
I have a JMenu and When I click on a JItem a JPanel is displayed but while it is being charged (some seconds... ) a gray rectangle remains instead the JMenu ...
do you know how to avoid this?Try putting the panel showing method/action in a SwingUtilities.invokeLater call
ICE -
Problems with disappearing JTextArea when activating JMenu
Im having trouble with using JTextArea in conjunction with JMenu and JInternalFrame. I have a program that uses JInternalFrames for navigation, when the navigation been used I set the JInternalFrame to setVisible(false) and display a JMenuBar with several components and a JTextArea. The JTextArea gets displayed as it should and so is the JMenuBar but when a JMenuItem has been activated the JTextArea becomes invisible or partly invisible. Anyone have any suggestions?
//Function that removes the JInternalFrame and adds the JMenuBar and JTextArea to the program
public void ordBehandlare()
ramnav.setVisible(false); //ramnav == JInternalFrame
Container cont = getContentPane();
cont.add(ordbehandlarArea); //ordbehandlarArea == JTextArea
setJMenuBar(ordBehandBar); //ordBehandBar == JMenuBar
Grateful for any answers...From the 5 lines of code you posted I have no idea whats wrong, but I'm sure you can create a 20 line program that we can compile and execute that demonstrates your problem. Chances are while your creating this simple program you will find your error.
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Focus Problem with JTree and Menus
Hi all,
I have a problem with focus when editing a JTree and selecting a menu. The problem occurs when the user single clicks on a node, invoking the countdown to edit. If the user quickly clicks on a menu item, the focus will go to the menu item, but then when the countdown finishes, the node now has keyboard focus.
Below is code to reproduce the problem. Click on the node, hover for a little bit, then quickly click on the menu item.
How would I go about fixing the problem? Thanks!
import java.awt.Container;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
public class MyTree extends JTree {
public MyTree(DefaultTreeModel treemodel) {
setModel(treemodel);
setRootVisible(true);
public static void main(String[] args) {
JFrame frame = new JFrame();
JMenuBar bar = new JMenuBar();
JMenu menu = new JMenu("Test");
JMenuItem item = new JMenuItem("Item");
menu.add(item);
bar.add(menu);
frame.setJMenuBar(bar);
Container contentPane = frame.getContentPane();
contentPane.setLayout(new GridLayout(1, 2));
DefaultMutableTreeNode root1 = new DefaultMutableTreeNode("Root");
root1.add(new DefaultMutableTreeNode("Root2"));
DefaultTreeModel model = new DefaultTreeModel(root1);
MyTree tree1 = new MyTree(model);
tree1.setEditable(true);
tree1.setCellEditor(
new ComponentTreeCellEditor(
tree1,
new ComponentTreeCellRenderer()));
tree1.setRowHeight(0);
contentPane.add(tree1);
frame.pack();
frame.show();
import java.awt.FlowLayout;
import java.util.EventObject;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.JTree;
import javax.swing.tree.DefaultTreeCellEditor;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeCellEditor;
import javax.swing.tree.TreeCellRenderer;
public class ComponentTreeCellEditor
extends DefaultTreeCellEditor
implements TreeCellEditor {
private String m_oldValue;
private TreeCellRenderer m_renderer = null;
private DefaultTreeModel m_model = null;
private JPanel m_display = null;
private JTextField m_field = null;
private JTree m_tree = null;
public ComponentTreeCellEditor(
JTree tree,
DefaultTreeCellRenderer renderer) {
super(tree, renderer);
m_renderer = renderer;
m_model = (DefaultTreeModel) tree.getModel();
m_tree = tree;
m_display = new JPanel(new FlowLayout(FlowLayout.LEFT));
m_field = new JTextField();
m_display.add(new JLabel("My Label "));
m_display.add(m_field);
public java.awt.Component getTreeCellEditorComponent(
JTree tree,
Object value,
boolean isSelected,
boolean expanded,
boolean leaf,
int row) {
m_field.setText(value.toString());
return m_display;
public Object getCellEditorValue() {
return m_field.getText();
* The edited cell should always be selected.
* @param anEvent the event that fired this function.
* @return true, always.
public boolean shouldSelectCell(EventObject anEvent) {
return true;
* Only edit immediately if the event is null.
* @param event the event being studied
* @return true if event is null, false otherwise.
protected boolean canEditImmediately(EventObject event) {
return (event == null);
}You can provide a cell renderer to the JTree to paint the checkBox.
The following code checks or unchecks the box with each click also:
_tree.setCellRenderer(new DefaultTreeCellRenderer()
private JCheckBox checkBox = null;
public Component getTreeCellRendererComponent(JTree tree,
Object value,
boolean selected,
boolean expanded,
boolean leaf,
int row,
boolean hasFocus)
// Each node will be drawn as a check box
if (checkBox == null)
checkBox = new JCheckBox();
checkBox .setBackground(tree.getBackground());
DefaultMutableTreeNode node = (DefaultMutableTreeNode)value;
checkBox.setText(node.getUserObject().toString());
checkBox.setSelected(selected);
return checkBox;
}); -
Problem with JMenus that Persist - Is this a Java bug?
I am having a problem with JMenus that persist. By this I mean
that my drop down menus persist on the screen even after they have
been selected.
I've checked the Java bug database, and the following seems
to come closest to my problem:
Bug ID: 4235188
JPopupMenus and JMenus persist when their JFrame becomes visible
State: Closed, not a bug
http://developer.java.sun.com/developer/bugParade/bugs/4235188.html
This page says that the matter is closed and is not a bug. The
resolution of this matter printed at the bottom of the page
is completely abstruse to me and I would appreciate any
comments to understand what they are talking about.
The code at the end of my message illustrates my problem.
1. Why should paintComponent() make any difference to
Menu behavior?
2. Is this a bug?
3. What's the workaround if I have to paint() or repaint()?
Thanks
Tony Lin
// Example of Menu Persistence Problem
// Try running this with line 41, paintComponent(), and without line 41
// Menus behave normally if line 41 is commented out
// If line 41 exists, menus will persist after they have been selected
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class P2 extends JPanel {
JMenuItem[] mi;
public P2() {
JFrame thisFrame = new JFrame();
thisFrame.getContentPane().add(this);
JMenu menu = new JMenu("My Menu");
JMenuBar mb = new JMenuBar();
mi = new JMenuItem[4];
for (int i=0; i<mi.length; i++) {
mi[i] = new JMenuItem("Menu Item " + String.valueOf(i));
menu.add(mi);
mb.add(menu);
thisFrame.setJMenuBar(mb);
thisFrame.setSize(400,200);
thisFrame.setLocation(150,200);
thisFrame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent we) {
System.exit(0);
thisFrame.setVisible(true);
public void paintComponent(Graphics g) {} //Affects menu behavior!
public static void main(String[] args) {
new P2();Well, my understanding of the way painting works is that a component doesn't UNPAINT itself. Instead a message is sent to the component under the coordinates of the menu to REPAINT itself.
In your demo program the JFrame is the component under the JMenu. The paintComponent() method of JFrame is empty, so nothing gets repainted.
I added super.paintComponent(g); to the method and everything works fine. -
Hi all...
I have a Menu called ActionEvents which has a JMenu called mouseEvents. What I want is to add a submenu to this (mouseEvents), I tried the following:
mouseEvents.add(new JMenuItem("New Item"));This compiles fine but doesnt show up on the application. However if I add another JMenu to ActionEvents e.g submenu as below, it adds the submenuItem to submenu.
JMenu submenu = new JMenu("submenu");
eventsMenu.add(submenu);
submenu.add(new JMenuItem("submenuItem"));Works fine for submenu but not mouseEvents.
Does any one have any ideas?
Thanks for any assiatance...Maybe I should take this to the bug report forum, but I was wondering if it might not be me. I'm pretty sure it isn't, but it is such a big problem I can't believe it would have not been caught and fixed before.
BTW, there is no problem with implementing submenus in AWT. -
i have problem with my program i implement saveing method
but when i open file( game.txt) it does not update my board it return same postion every time i same game
chess class Jframe(Jfilechooser)(call an board array)---->
Gui Japplet class( call and board array------------>
Board(class Jpanel have board array)
it does not update borad array
it just call it once in start and return the same value every time
classChess(){
ChessPlayer java = new ChessPlayer();
public void saveData()
File file = null;
JFileChooser fc = new JFileChooser();
fc.setCurrentDirectory(new File("."));
fc.setDialogTitle("Save Text As...");
int returnVal = fc.showSaveDialog(this);
if (returnVal == JFileChooser.APPROVE_OPTION)
{ file = fc.getSelectedFile();
try
{ PrintWriter out =
new PrintWriter(
new BufferedWriter(
new FileWriter(file)));
//while for all the moves in the array>
for (int i=0;i<120;i++)
out.println( java.saveDAta(i));
out.println("\n");
out.close();
catch (IOException e) {
// Some error has occured while trying to read the file.
// Show an error message.
JOptionPane.showMessageDialog(this,
"Sorry, some error occurred:\n" + e.getMessage());}
public static void main(String[] args) {
JPopupMenu.setDefaultLightWeightPopupEnabled(false);
JFrame frame = new ChessMan();
Container content = frame.getContentPane();
ChessMan f = new ChessMan();
//japplet
ChessPlayer javaAppletication = new ChessPlayer();
javaAppletication.init();
javaAppletication.start();
}Gui
[Gui]
class Gui{
int [] board = new int [120];
int [] boardcolor = new int [120];
Board check = new Board(this,false);
{public void init()
{ // Create new Border
contentPane = getContentPane();
bboard = new Board(this,false);
public String saveDAta(int i)
String l=check. save(i);
return (l);
and finally board Jpanel
class Board extends JPanel
{public Board (JApplet useapplet,boolean bool) {
setup();
{ public String save(int i)
{ String l;
if (color==1)
{System.out.println("notpossible");}
l = board[i]+"$"+boardColor;
return l;
thanks guysMy Jframe
public class ChessMan extends JFrame implements ActionListener, WindowListener {
JMenuItem saveItem, loadItem, copyItem, pasteItem;
JMenu fileMenu, editMenu;
JMenuBar bar;
ChessPlayer java = new ChessPlayer();
public ChessMan() { setTitle("CHESS PLAYER GAME" );
setSize(200,300);
System.out.println("\n"); }
addWindowListener(new java.awt.event.WindowAdapter()
{ public void windowClosing(java.awt.event.WindowEvent e)
{ System.exit(0); } });
JMenu fileMenu = new JMenu("File");
saveItem = new JMenuItem("Save");
saveItem.setActionCommand("save");
saveItem.setAccelerator( KeyStroke.getKeyStroke("ctrl S"));
saveItem.addActionListener(this);
fileMenu.add(saveItem);
loadItem = new JMenuItem("Load");
loadItem.setActionCommand("load");
loadItem.setAccelerator( KeyStroke.getKeyStroke("ctrl L"));
loadItem.addActionListener(this);
fileMenu.add(loadItem);
JMenu editMenu = new JMenu("About");
copyItem = new JMenuItem("Help");
copyItem.setActionCommand("Help");
copyItem.setAccelerator( KeyStroke.getKeyStroke("ctrl H"));
copyItem.addActionListener(this);
editMenu.add(copyItem);
pasteItem = new JMenuItem("Exit");
pasteItem.setActionCommand("Exit");
pasteItem.setAccelerator( KeyStroke.getKeyStroke("ctrl E"));
pasteItem.addActionListener(this);
editMenu.add(pasteItem);
JMenuBar bar = new JMenuBar();
bar.add(fileMenu);
bar.add(editMenu);
setJMenuBar(bar);
setVisible(true);
setLocation(0,0);
public void actionPerformed(ActionEvent e) {
JMenuItem item = (JMenuItem)e.getSource();
String ac = item.getActionCommand();
System.out.println("ac = "+ ac);
// you can use action commands to track menu item events
if(ac.equals("save"))
{System.out.println("ac.equals(\"save\") = "+ ac.equals("save"));
saveData();}
if(ac.equals("load"))
{System.out.println("ac.equals(\"load\") = "+ ac.equals("load"));
loadingData();}
if(ac.equals("Help"))
{System.out.println("ac.equals(\"load\") = "+ ac.equals("Help"));
if(ac.equals("Exit"))
{System.out.println("ac.equals(\"load\") = "+ ac.equals("Exit"));
Exit();}
// the event origin
if(item == saveItem)
System.out.println("item = "+ item.toString().substring
(item.toString().indexOf("text=") + 5, item.toString().lastIndexOf("]")));
if(item == loadItem)
System.out.println("item = "+ item);
// System.out.print( java.saveDAta());
public void saveData()
File file = null;
JFileChooser fc = new JFileChooser();
fc.setCurrentDirectory(new File("."));
fc.setDialogTitle("Save Text As...");
int returnVal = fc.showSaveDialog(this);
if (returnVal == JFileChooser.APPROVE_OPTION)
{ file = fc.getSelectedFile();
try
{ PrintWriter out =
new PrintWriter(
new BufferedWriter(
new FileWriter(file)));
//while for all the moves in the array>
for (int i=0;i<120;i++)
out.println( java.saveDAta(i));
out.println("\n");
out.close();
catch (IOException e) {
// Some error has occured while trying to read the file.
// Show an error message.
JOptionPane.showMessageDialog(this,
"Sorry, some error occurred:\n" + e.getMessage());}
public void loadingData()
File loadfile = null;
JFileChooser fc = new JFileChooser();
fc.setDialogTitle("OpenFile...");
fc.setCurrentDirectory(new File("."));
int returnVal = fc.showOpenDialog(this);
if (returnVal == JFileChooser.APPROVE_OPTION)
{ loadfile = fc.getSelectedFile();
try
{ PrintWriter out =
new PrintWriter(
new BufferedWriter(
new FileWriter(loadfile)));
//while for all the moves in the array>
out.println("�����������������");
out.println("\n");
out.close();
catch (IOException e) {
// Some error has occured while trying to read the file.
// Show an error message.
JOptionPane.showMessageDialog(this,
"Sorry, some error occurred:\n" + e.getMessage());}
public void Exit()
System.exit(0);
public static void main(String[] args) {
JPopupMenu.setDefaultLightWeightPopupEnabled(false);
JFrame frame = new ChessMan();
Container content = frame.getContentPane();
ChessMan f = new ChessMan();
f.setLocation(300,300);
f.show();
ImageIcon customImageIcon = new ImageIcon("ac516.gif");
Image customImage = customImageIcon.getImage();
frame.setIconImage(customImage);
//japplet
ChessPlayer javaAppletication = new ChessPlayer();
// i could not put my constructor here <Static>
javaAppletication.init();
javaAppletication.start();
// for(int i=0; i < .length(); i++)
content.add(javaAppletication, BorderLayout.CENTER);
frame.getContentPane();
javaAppletication.setBackground (Color.black);
frame.setVisible(true);
frame.show();
frame.pack(); // invokes getPreferredSize()
// invokes paint();
public void windowOpened(WindowEvent e) {
fileMenu.doClick();
public void windowClosing(WindowEvent e) {}
public void windowClosed(WindowEvent e) {}
public void windowIconified(WindowEvent e) {}
public void windowDeiconified(WindowEvent e) {}
public void windowActivated(WindowEvent e) {}
public void windowDeactivated(WindowEvent e) {}
My Japplet Class
class ChessPlayer extends JApplet
implements ActionListener,MouseListener
int c;
//Reference for new Board
Board bboard;
//Reference for Button
JButton newgame,undo,onePlayer,TwoPlayer,NormalPieceSet,
FuunyPieceSet,startButton,stopButton;
//Reference for Label
JLabel message;
//Reference for new Panel
JPanel buttonpanel2,buttonpanel,messagepanel,buttonpane;
//Initilize the Applet
DemoAnimation Demo;
Container contentPane;
Board check = new Board(this,false);
int [] board = new int [120];
int [] boardcolor = new int [120];
public void init()
// Create new Border
contentPane = getContentPane();
check = new Board(this,false);
bboard = new Board(this,false);
bboard.setPreferredSize(new Dimension(500,400));
bboard.setBorder(BorderFactory.createLineBorder( Color.red ) );
contentPane.add(bboard);
final ImageIcon image = new ImageIcon("ac516.gif");
bboard.addMouseListener(this);
bboard.setBackground (Color.black);
BorderLayout text=new BorderLayout();
Demo = new DemoAnimation( this );
Demo.setPreferredSize(new Dimension(160, 500));
contentPane.add(Demo);
// Set Background Black
contentPane.setBackground (Color.black);
contentPane.setLayout (new BorderLayout (50,50));
// set new Font "TimesRoman"
Font Text= new Font("TimesRoman", Font.BOLD,15);
//panel to keep buttons together
buttonpanel=new JPanel();
buttonpanel.setLayout(new GridLayout(1,2,6,0));
buttonpanel.add(newgame=new JButton("new game",image));
newgame.addActionListener(this);
buttonpanel.add(undo=new JButton("undo"));
undo.addActionListener(this);
// Create new Choice Panel
buttonpanel2 = new JPanel();
buttonpanel2.setLayout(new GridLayout(6,1,0,10));
buttonpanel2.add(onePlayer=new JButton("Change Colour"));
onePlayer.addActionListener(this);
buttonpanel2.add(TwoPlayer=new JButton("Statistic"));
TwoPlayer.addActionListener(this);
buttonpanel2.add(NormalPieceSet=new JButton("Quit"));
NormalPieceSet.addActionListener(this);
buttonpanel2.add(FuunyPieceSet=new JButton("Change Piece"));
FuunyPieceSet.addActionListener(this);
buttonpanel2.add(startButton = new JButton("Start Animation"));
startButton.addActionListener(this);
buttonpanel2.add(stopButton = new JButton("Stop Animation"));
stopButton.addActionListener(this);
contentPane.add(BorderLayout.WEST, demopanel);
// Set Font For Text Message
setFont(Text);
messagepanel=new JPanel();
messagepanel.setBorder(BorderFactory.createLineBorder( Color.red ) );
messagepanel.setBackground(Color.black);
// essagepanel.setLayout(new GridLayout(1,1));
// Create new Label
messagepanel.add(message = new JLabel());
setMessage("Welcome");
// Postion panels in Layout
contentPane.add("North",buttonpanel);
contentPane.add("East",buttonpanel2);
contentPane.add ("South",messagepanel);
contentPane.add ("Center",bboard);
contentPane.add("West",Demo);
public void mouseReleased(java.awt.event.MouseEvent e)
{ statuseChange();}
public void mouseClicked(java.awt.event.MouseEvent e)
public void mouseEntered(java.awt.event.MouseEvent e) {
public void mouseExited(java.awt.event.MouseEvent e) {
public void mouseMoved(java.awt.event.MouseEvent e) {
statuseChange();
public void mousePressed(java.awt.event.MouseEvent e)
{statuseChange();
public void actionPerformed(ActionEvent e)
Object source=e.getSource();
if (source == newgame)
{ bboard.newgame();
yellow();
setMessage("try again");
pause(100);
c=add(c);
else if (source==undo)
yellow();
bboard.undo();
setMessage("Undo");
else if (source== TwoPlayer )
//bboard.setup();
yellow();
setMessage("Starting new Game");
setMessage("Change Color");
else if(source == FuunyPieceSet)
{yellow();
setMessage("game played::" +c);
bboard.PieceChange();
else if(source == NormalPieceSet)
{yellow();
setMessage("GOODBYE");
destroy();
else if(source == startButton)
{yellow();
setMessage("Start Animation");
Demo.start();
else if(source == stopButton)
{yellow();
setMessage("Stop Animation");
Demo.stop();
else if(source == onePlayer)
{setMessage("");
bboard.changePiece();
setMessage("Change Color");
public void statuseChange()
switch (bboard.gameStatus())
case 1:
red();
setMessage("White won");
break;
case 2:
red();
setMessage("Black won");
break;
case 3:
red();
setMessage("DRAW");
Demo.changeAnimation(2);
break;
case 4:
white();
setMessage("White Turn");
Demo.changeAnimation(1);
break;
case 5:
green();
setMessage("Black turn");
Demo.changeAnimation(3);
break;
case 6:
red();
setMessage(" Check");
Demo.changeAnimation(4);
break;
case 7:
red();
setMessage("Check");
Demo.changeAnimation(4);
break;
case 8:
yellow();
setMessage("I Hope you enjoyed it");
public String saveDAta(int i)
String l=check.save(i);
return (l);
public void LoadData(String load)
public void setMessage(String s)
/*The string s will be shown to the user.*/
Font Text= new Font("Courier", Font.BOLD,30);
message.setText(s);
message.setFont(Text);
public void white()
{ message.setForeground(Color.white);}
public void green()
message.setForeground(Color.green);
public void red()
message.setForeground(Color.red);
public void yellow()
message.setForeground(Color.yellow);
// pause method
void pause(int time)
try {Thread.sleep(time);
} catch (InterruptedException e)
// Create new inset Object
public Insets getInsets()
return new Insets(50,220,150,200);
public void destroy()
contentPane.remove(buttonpanel2);
contentPane.remove(buttonpanel);
contentPane.remove(bboard);
contentPane.repaint();
Demo.start();
public int add(int x)
{ int b=x+1;
return b;
}tanx man i dont the other two because they are to long
my is when i open jframe
i think Japplet and Jframe can not commuinicate to each other -
I am trying to implement some kind of a server listening for requests. The listener part of the app, is a daemon thread that listens for connections and instantiates a handling daemon thread once it gets some. However, my problem is that i must be able to kill the listening thread at the user's will (say via a sto button). I have done this via the Sun's proposed way, by testing a boolean flag in the loop, which is set to false when i wish to kill the thread. The problem with this thing is the following...
Once the thread starts excecuting, it will test the flag, find it true and enter the loop. At some point it will LOCK on the server socket waiting for connection. Unless some client actually connects, it will keep on listening indefinatelly whithought ever bothering to check for the flag again (no matter how many times you set the damn thing to false).
My question is this: Is there any real, non-theoretical, applied way to stop thread in java safely?
Thank you in advance,
LeftyThis was one solution from the socket programming forum, have you tried this??
public Thread MyThread extends Thread{
boolean active = true;
public void run(){
ss.setSoTimeout(90);
while (active){
try{
serverSocket = ss.accept();
catch (SocketTimeoutException ste){
// do nothing
// interrupt thread
public void deactivate(){
active = false;
// you gotta sleep for a time longer than the
// accept() timeout to make sure that timeout is finished.
try{
sleep(91);
}catch (InterruptedException ie){
interrupt();
} -
Problem with Threads and a static variable
I have a problem with the code below. I am yet to make sure that I understand the problem. Correct me if I am wrong please.
Code functionality:
A timer calls SetState every second. It sets the state and sets boolean variable "changed" to true. Then notifies a main process thread to check if the state changed to send a message.
The problem as far I understand is:
Assume the timer Thread calls SetState twice before the main process Thread runs. As a result, "changed" is set to true twice. However, since the main process is blocked twice during the two calls to SetState, when it runs it would have the two SetState timer threads blocked on its synchronized body. It will pass the first one, send the message and set "changed" to false since it was true. Now, it will pass the second thread, but here is the problem, "changed" is already set to false. As a result, it won't send the message even though it is supposed to.
Would you please let me know if my understanding is correct? If so, what would you propose to resolve the problem? Should I call wait some other or should I notify in a different way?
Thanks,
B.D.
Code:
private static volatile boolean bChanged = false;
private static Thread objMainProcess;
protected static void Init(){
objMainProcess = new Thread() {
public void run() {
while( objMainProcess == Thread.currentThread() ) {
GetState();
objMainProcess.setDaemon( true );
objMainProcess.start();
public static void initStatusTimer(){
if(objTimer == null)
objTimer = new javax.swing.Timer( 1000, new java.awt.event.ActionListener(){
public void actionPerformed( java.awt.event.ActionEvent evt){
SetState();
private static void SetState(){
if( objMainProcess == null ) return;
synchronized( objMainProcess ) {
bChanged = true;
try{
objMainProcess.notify();
}catch( IllegalMonitorStateException e ) {}
private static boolean GetState() {
if( objMainProcess == null ) return false;
synchronized( objMainProcess ) {
if( bChanged) {
SendMessage();
bChanged = false;
return true;
try {
objMainProcess.wait();
}catch( InterruptedException e ) {}
return false;
}Thanks DrClap for your reply. Everything you said is right. It is not easy to make them alternate since SetState() could be called from different places where the state could be anything else but a status message. Like a GREETING message for example. It is a handshaking message but not a status message.
Again as you said, There is a reason I can't call sendMessage() inside setState().
The only way I was able to do it is by having a counter of the number of notifies that have been called. Every time notify() is called a counter is incremented. Now instead of just checking if "changed" flag is true, I also check if notify counter is greater than zero. If both true, I send the message. If "changed" flag is false, I check again if the notify counter is greater than zero, I send the message. This way it works, but it is kind of a patch than a good design fix. I am yet to find a good solution.
Thanks,
B.D. -
Problem with threads running javaw
Hi,
Having a problem with multi thread programming using client server sockets. The program works find when starting the the application in a console using java muti.java , but when using javaw multi.java the program doesnt die and have to kill it in the task manager. The program doesnt display any of my gui error messages either when the server disconnect the client. all works find in a console. any advice on this as I havent been able to understand why this is happening? any comment would be appreciated.
troy.troy,
Try and post a minimum code sample of your app which
does not work.
When using javaw, make sure you redirect the standard
error and standard output streams to file.
Graeme.Hi Graeme,
I dont understand what you mean by redirection to file? some of my code below.
The code works fine under a console, code is supposed to exit when the client (the other server )disconnects. the problem is that but the clientworker side of the code still works. which under console it doesnt.
public class Server{
ServerSocket aServerSocket;
Socket dianosticsSocket;
Socket nPortExpress;
ClientListener aClientListener;
LinkedList queue = new LinkedList();
int port = 0;
int clientPort = 0;
String clientName = null;
boolean serverAlive = true;
* Server constructor generates a server
* Socket and then starts a client threads.
* @param aPort socket port of local machine.
public Server(int aPort, String aClientName, int aClientPort){
port = aPort;
clientName = aClientName;
clientPort = aClientPort;
try{
// create a new thread
aServerSocket = new ServerSocket(port) ;
// connect to the nPortExpress
aClientListener = new ClientListener(InetAddress.getByName(clientName), clientPort, queue,this);
// aClientListener.setDaemon(true);
aClientListener.start();
// start a dianostic port
DiagnosticsServer aDiagnosticsServer = new DiagnosticsServer(port,queue,aClientListener);
// System.out.println("Server is running on port " + port + "...");
// System.out.println("Connect to nPort");
catch(Exception e)
// System.out.println("ERROR: Server port " + port + " not available");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Server port " + port + " not available", JOptionPane.ERROR_MESSAGE);
serverAlive = false;
System.exit(1);
while(serverAlive&&aClientListener.hostSocket.isConnected()){
try{
// connect the client
Socket aClient = aServerSocket.accept();
//System.out.println("open client connection");
//System.out.println("client local: "+ aClient.getLocalAddress().toString());
// System.out.println("client localport: "+ aClient.getLocalPort());
// System.out.println("client : "+ aClient.getInetAddress().toString());
// System.out.println("client port: "+ aClient.getLocalPort());
// make a new client thread
ClientWorker clientThread = new ClientWorker(aClient, queue, aClientListener, false);
// start thread
clientThread.start();
catch(Exception e)
//System.out.println("ERROR: Client connection failure");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Client connection failure", JOptionPane.ERROR_MESSAGE);
}// end while
} // end constructor Server
void serverExit(){
JOptionPane.showMessageDialog(null, "Server ","ERROR: nPort Failure", JOptionPane.ERROR_MESSAGE);
System.exit(1);
}// end class Server
*** connect to another server
public class ClientListener extends Thread{
InetAddress hostName;
int hostPort;
Socket hostSocket;
BufferedReader in;
PrintWriter out;
boolean loggedIn;
LinkedList queue; // reference to Server queue
Server serverRef; // reference to main server
* ClientListener connects to the host server.
* @param aHostName is the name of the host eg server name or IP address.
* @param aHostPort is a port number of the host.
* @param aLoginName is the users login name.
public ClientListener(InetAddress aHostName, int aHostPort,LinkedList aQueue,Server aServer) // reference to Server queue)
hostName = aHostName;
hostPort = aHostPort;
queue = aQueue;
serverRef = aServer;
// connect to the server
try{
hostSocket = new Socket(hostName, hostPort);
catch(IOException e){
//System.out.println("ERROR: Connection Host Failed");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Connection to nPort Failed", JOptionPane.ERROR_MESSAGE);
System.exit(0);
} // end constructor ClientListener
** multi client connection server
ClientWorker(Socket aSocket,LinkedList aQueue, ClientListener aClientListener, boolean diagnostics){
queue = aQueue;
addToQueue(this);
client = aSocket;
clientRef = aClientListener;
aDiagnostic = diagnostics;
} // end constructor ClientWorker
* run method is the main loop of the server program
* in change of handle new client connection as well
* as handle all messages and errors.
public void run(){
boolean alive = true;
String aSubString = "";
in = null;
out = null;
loginName = "";
loggedIn = false;
while (alive && client.isConnected()&& clientRef.hostSocket.isConnected()){
try{
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(client.getOutputStream()));
if(aDiagnostic){
out.println("WELCOME to diagnostics");
broadCastDia("Connect : diagnostics "+client.getInetAddress().toString());
out.flush();
else {
out.println("WELCOME to Troy's Server");
broadCastDia("Connect : client "+client.getInetAddress().toString());
out.flush();
String line;
while(((line = in.readLine())!= null)){
StringTokenizer aStringToken = new StringTokenizer(line, " ");
if(!aDiagnostic){
broadCastDia(line);
clientRef.sendMessage(line); // send mesage out to netExpress
out.println(line);
out.flush();
else{
if(line.equals("GETIPS"))
getIPs();
else{
clientRef.sendMessage(line); // send mesage out to netExpress
out.println(line);
out.flush();
} // end while
catch(Exception e){
// System.out.println("ERROR:Client Connection reset");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR:Client Connection reset", JOptionPane.ERROR_MESSAGE);
try{
if(aDiagnostic){
broadCastDia("Disconnect : diagnostics "+client.getInetAddress().toString());
out.flush();
else {
broadCastDia("Disconnect : client "+client.getInetAddress().toString());
out.flush();
// close the buffers and connection;
in.close();
out.close();
client.close();
// System.out.println("out");
// remove from list
removeThreadQueue(this);
alive = false;
catch(Exception e){
// System.out.println("ERROR: Client Connection reset failure");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Client Connection reset failure", JOptionPane.ERROR_MESSAGE);
}// end while
} // end method run
* method run - Generates io stream for communicating with the server and
* starts the client gui. Run also parses the input commands from the server.
public void run(){
boolean alive = true;
try{
// begin to life the gui
// aGuiClient = new ClientGui(hostName.getHostName(), hostPort, loginName, this);
// aGuiClient.show();
in = new BufferedReader(new InputStreamReader(hostSocket.getInputStream()));
out = new PrintWriter(new OutputStreamWriter(hostSocket.getOutputStream()));
while (alive && hostSocket.isConnected()){
String line;
while(((line = in.readLine())!= null)){
System.out.println(line);
broadCast(line);
} // end while
} // end while
catch(Exception e){
// System.out.println("ERRORa Connection to host reset");
JOptionPane.showMessageDialog(null, (e.toString()),"ERROR: Connection to nPort reset", JOptionPane.ERROR_MESSAGE);
try{
hostSocket.close();
}catch(Exception a){
JOptionPane.showMessageDialog(null, (a.toString()),"ERROR: Exception", JOptionPane.ERROR_MESSAGE);
alive = false;
System.exit(1);
} // end method run -
Problem with threads and camera.
Hi everybody!
I've a problem with taking snapshot.
I would like to display a loading screen after it take snapshot ( sometimes i
have to wait few seconds after i took snapshot. Propably photo is being taken in time where i have to wait).
I was trying to use threads but i didn't succeed.
I made this code:
display.setCurrent(perform);
new Thread(new Runnable(){
public void run() {
while((!performing.isShown()) && (backgroundCamera.isShown())){
Thread.yield();
notifyAll();
}).start();
new Thread(new Runnable(){
public void run() {
try {
this.wait();
} catch(Exception e) {
exceptionHandler(e);
photo = camera.snapshot();
display.setCurrent(displayPhoto);
}).start();This code is sometimes showing performing screen but sometimes no.
I don't know why. In my opinion performing.isShown() method isn't working correctly.
Does anyone have some idea how to use threads here?Hi,
I've finally managed to work this fine.
The code:
Object o = new Object();
display.setCurrent(perform);
new Thread(new Runnable(){
public void run() {
while(!performing.isShown()){
Thread.yield();
synchronized(o) {
o.notify();
}).start();
new Thread(new Runnable(){
public void run() {
try {
synchronized(o) {
o.wait(1);
} catch(Exception e) {
exceptionHandler(e);
photo = camera.snapshot();
display.setCurrent(displayPhoto);
}).start(); -
We have a problem where our application stops responding after a few days of usage. Things will for fine for a day or two, and then pretty quickly threads will start getting hung up, usually in places where they are allocating memory
We are running WebLogic 8.1 SP2 on Sun JDK 1.4.2_04 on Solaris 8 using the alternate threading model and the -server hotspot vm. We are running pretty much the same code that we had no problems with under WebLogic 6.1 SP4 and Sun JDK 1.3.1.
A thread dump usually shows that some or all of our execute threads are in the state "waiting for monitor entry" even though they are not currently waiting on any java locks. Here is a sample thread from the thread dump (we have ~120 threads so I don't want to post the full dump).
=============================================================================================
"ExecuteThread: '8' for queue: 'itgCrmWarExecutionQueue'" daemon prio=5 tid=0x005941d0 nid=0x2c waiting for monitor entry [c807f000..c807fc28]
at java.lang.String.substring(String.java:1446)
at java.lang.String.substring(String.java:1411)
at weblogic.servlet.internal.ServletRequestImpl.getRelativeUri(ServletRequestImpl.java:1872)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3492)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2585)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:197)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:170)
=============================================================================================
String.java line 1446 for this jdk allocates a new String object, and all the other threads in this state also are creating new objects or arrays, etc.
We've done a pstack on this process when it's in this state, and the threads that are in the "waiting for monitor entry" that look like they're allocating memory are all waiting on the same lwp_mutex_lock with some allocation method that's calling into the native TwoGenerationCollectorPolicy.mem_allocate_work (see pstack output below for the same thread as in the thread dump above)
=============================================================================================
----------------- lwp# 44 / thread# 44 --------------------
ff31f364 lwp_mutex_lock (e3d70)
fee92384 __1cNObjectMonitorGenter26MpnGThread__v_ (5000, 525c, 5000, 50dc, 4800, 4af0) + 2d8
fee324d4 __1cSObjectSynchronizerKfast_enter6FnGHandle_pnJBasicLock_pnGThread__v_ (c807f65c, c807f7d4, 5941d0, 0, 35d654, fee328ec) + 68
fee32954 __1cQinstanceRefKlassZacquire_pending_list_lock6FpnJBasicLock__v_ (c807f7d4, ff170000, d4680000, 4491d4, fee1bc2c,
0) + 78
fee3167c __1cPVM_GC_OperationNdoit_prologue6M_i_ (c807f7bc, 4400, ff170000, 2d2b8, 4a6268, c807fa18) + 38
fee2e0b0 __1cIVMThreadHexecute6FpnMVM_Operation__v_ (c807f7bc, 963a8, 0, 0, 1, 0) + 90
fed2c2a4 __1cbCTwoGenerationCollectorPolicyRmem_allocate_work6MIii_pnIHeapWord__ (962c0, ff1c29ec, ff1c297c, ff131a26, 4800, 4998) + 160
fed22940 __1cNinstanceKlassRallocate_instance6MpnGThread__pnPinstanceOopDesc__ (ee009020, 5941d0, 15ca581, 3647f0, 4a6268, c807f8c8) + 180
fed34928 __1cLOptoRuntimeFnew_C6FpnMklassOopDesc_pnKJavaThread__v_ (ee009018, 5941d0, 0, 0, 0, 0) + 28
fa435a58 ???????? (ee009018, e86de, 15ca4de, 50dc, 5941d0, c807f9c8)
fb36f9a4 ???????? (0, d412ccd8, ee046c28, ff170000, 0, 0)
fad8b278 ???????? (ee046c28, d6000c90, ee046530, 8, db8e8450, c807f9e8)
fad62abc ???????? (d412ccd8, ee046530, d6000c90, ee3bfa38, 8, c807fa18)
fa4b3c38 ???????? (c807fb9c, 0, f2134700, fa415e50, 8, c807faa8)
fa40010c ???????? (c807fc28, c807fe90, a, ee9e1e20, 4, c807fb40)
fed5d48c __1cJJavaCallsLcall_helper6FpnJJavaValue_pnMmethodHandle_pnRJavaCallArguments_pnGThread__v_ (c807fe88, c807fcf0, c807fda8, 5941d0, 5941d0, c807fd00) + 27c
fee4b784 __1cJJavaCallsMcall_virtual6FpnJJavaValue_nLKlassHandle_nMsymbolHandle_4pnRJavaCallArguments_pnGThread__v_ (ff170000, 594778, c807fd9c, c807fd98, c807fda8, 5941d0) + 164
fee5e8dc __1cJJavaCallsMcall_virtual6FpnJJavaValue_nGHandle_nLKlassHandle_nMsymbolHandle_5pnGThread__v_ (c807fe88, c807fe84, c807fe7c, c807fe74, c807fe6c, 5941d0) + 6c
fee6fc74 __1cMthread_entry6FpnKJavaThread_pnGThread__v_ (5941d0, 5941d0, 838588, 594778, 306d10, fee69254) + 128
fee6927c __1cKJavaThreadDrun6M_v_ (5941d0, 2c, 40, 0, 40, 0) + 284
fee6575c _start (5941d0, fa1a1600, 0, 0, 0, 0) + 134
ff3758c0 lwpstart (0, 0, 0, 0, 0, 0)
=============================================================================================
Also when it's having this problem, the "VM Thread" is always using a lot of processor time. We did a couple of pstacks today while it was having this problem, and this thread was stuck in the ONMethodSweeper.sweep for over 15 minutes when we finally killed the server.
From the thread dump:
"VM Thread" prio=5 tid=0x000e2d20 nid=0x2 runnable
From the first pstack:
=============================================================================================
----------------- lwp# 2 / thread# 2 --------------------
fed40c04 __1cXvirtual_call_RelocationIparse_ic6FrpnICodeBlob_rpC5rppnHoopDesc_pi_nNRelocIterator__ (42a2f4, fa5fa46d, ffffffff, fc4ffcb8, 42a2f4, 42a324) + 124
fed46318 __1cKCompiledIC2t5B6MpnKRelocation__v_ (42a2f0, fc4ffd24, fc4ffd4c, e802, 0, 6) + 38
fed90c38 __1cHnmethodVcleanup_inline_caches6M_v_ (fa5f7f88, fa608940, 1, 0, fa400000, 6) + 1ac
fede18b4 __1cONMethodSweeperFsweep6F_v_ (2cf38, 0, ffffffff, ff1cf1fc, ff1c66e8, fede1d44) + 1b0
fede1e6c __1cUSafepointSynchronizeFbegin6F_v_ (2cf38, ff1ba138, 5000, 50dc, 5000, 525c) + 248
feef1fd4 __1cIVMThreadEloop6M_v_ (4400, 4000, 4324, 4000, 42b0, 3800) + 3d4
feef1ae4 __1cIVMThreadDrun6M_v_ (e2d20, 2, 40, 0, 40, 0) + 8c
fee6575c _start (e2d20, ff270200, 0, 0, 0, 0) + 134
ff3758c0 lwpstart (0, 0, 0, 0, 0, 0)
=============================================================================================
Second pstack
=============================================================================================
----------------- lwp# 2 / thread# 2 --------------------
fed41180 __1cXvirtual_call_RelocationIparse_ic6FrpnICodeBlob_rpC5rppnHoopDesc_pi_nNRelocIterator__ (0, ff1b9664, ffffffff, fc4ffcb8, a6f2cc, fc4ffbd0) + 6a0
fed46318 __1cKCompiledIC2t5B6MpnKRelocation__v_ (a6f2c8, fc4ffd24, fc4ffd4c, e802, 0, 6) + 38
fed90c38 __1cHnmethodVcleanup_inline_caches6M_v_ (faded4c8, fadf2c80, 1, 0, fa400000, 6) + 1ac
fede18b4 __1cONMethodSweeperFsweep6F_v_ (2cf38, 0, ffffffff, ff1cf1fc, ff1c66e8, fede1d44) + 1b0
fede1e6c __1cUSafepointSynchronizeFbegin6F_v_ (2cf38, ff1ba138, 5000, 50dc, 5000, 525c) + 248
feef1fd4 __1cIVMThreadEloop6M_v_ (4400, 4000, 4324, 4000, 42b0, 3800) + 3d4
feef1ae4 __1cIVMThreadDrun6M_v_ (e2d20, 2, 40, 0, 40, 0) + 8c
fee6575c _start (e2d20, ff270200, 0, 0, 0, 0) + 134
ff3758c0 lwpstart (0, 0, 0, 0, 0, 0)
=============================================================================================
Has anyone ever seen anything like this? I'm trying to figure out if this is caused by something we're doing, or something relating to our environment and jvm options. Any ideas?Thanks for the reply - I'm testing our app with the +UseConcMarkSweepGC now in our test environment to make sure it doesn't cause any problems there. Unfortunately the only place we've had this problem is on the production server, so it's extra difficult debugging this.
We're using the following memory options:
-ms512m -mx512m -XX:NewSize=128m -XX:PermSize=192m -XX:MaxNewSize=128m -XX:MaxPermSize=192m -XX:SurvivorRatio=8and the following debugging options, as we've also been seeing OutOfMemoryErrors ( see http://forum.java.sun.com/thread.jsp?forum=37&thread=522354&tstart=45&trange=15 )
-verbosegc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGCBTW, which c++filt version and options are you using? Our Solaris boxes only seem to have the GNU version installed. I was trying to run that on some of the other stack traces and wasn't getting anywhere, and didn't know if because it was GNU version wouldn't work on something compiled with the Sun compiler.
Thanks!
--Andy -
Problem with threads and ProgressMonitor
Dear Friends:
I have a little problem with a thread and a ProgressMonitor. I have a long time process that runs in a thread (the thread is in an separate class). The thread has a ProgressMonitor that works fine and shows the tasks progress.
But I need deactivate the main class(the main class is the user interface) until the thread ends.
I use something like this:
LongTask myTask=new LongTask();
myTask.start();
myTask.join();
Now, the main class waits for the task to end, but the progress monitor don`t works fine: it shows only the dialog but not the progress bar.
What's wrong?Is the dialog a modal dialog? This can block other UI updates.
In general, you should make sure that it isn't modal, and that your workThread has a fairly low priority so that the UI can do its updating
Maybe you are looking for
-
My conversation with a Verizon Rep concerning the iPhone shipments.
I understand that a lot of you think that the CSR's are not very knowledgeable about the shipment of our phones, and that may be the case, however I thought I would post my conversation that I just had with one. I added more to the bottome as I cont
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Past versions of iTunes for Windows had the annoying behavior that it couldn't be closed. If I tried to exit or close the window iTunes would just open back up again. It had gone away, but apple just installed version 11.1.5.5 and it's back! The only
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I need to find a Elephant Ringtone for my wife's Verizon cell phone. Where can I get? Thanks
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Need help change receive at email to receive to phone number
hi guys, i just a 4s and i setup imessage, but on my imessage settings it says "receive at email" and it wouldn't give me a option to put in my phone number. can you guys please help through this, thanks
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MS Office 2008 doesn't load after migration to MacBook Air
My daughter has a new MacBook Air 11" (2GHz i7, 256 GB SSD, 8GB DDR3 RAM). We used Migration Assistant and an ethernet to Thunderbolt adaptor to move her system from her Late 2007 MacBook running Lion. Microsoft Office 2008 won't load on the MacBoo