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.
Ralf
It 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.
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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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Hi,
i have a problem with the JMenu in a project.
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Anyone who knows this problem?
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int chars_per_line=20;
JFrame jf=new JFrame();
JTextArea jta=new JTextArea(24,chars_per_line);
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import java.awt.event.*;
import java.sql.*;
import javax.swing.*;
import javax.swing.event.*;
import java.io.*;
class MyFrame2 extends JFrame implements ActionListener{
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private JMenu j3 = new JMenu();
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j4.add(jm1);
j4.add(jm2);
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public class Db4
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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.
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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 ...
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Problem with JTextArea or is it my code, Help!!!
Hi,
I am going crazy. I am sending a message to a JTextArea and I get some very wierd things happening? I really need help because this is driving me crazy. Please see the following code to see my annotations for the problems. Has anyone else experienced problems with this component?
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// THIS IS THE CLASS THAT HANDLES ALL OF THE WORK
public class UpdateDataFields implements ActionListener { // 400
JTextArea msg;
JPanel frameForCardPane;
CardLayout cardPane;
TestQuestionPanel fromRadio;
public UpdateDataFields( JTextArea msgout ) { // 100
msg = msgout;
} // 100
public void actionPerformed(ActionEvent evt) { // 200
String command = evt.getActionCommand();
String reset = "Test of reset.";
try{
if (command.equals("TestMe")){ // 300
msg.append("\nSuccessful");
Interface.changeCards();
} // 300
catch(Exception e){
e.printStackTrace();
try{
if (command.equals("ButtonA")){ // 300
// WHEN I CALL BOTH OF THE FOLLOWING METHODS THE DISPLAY WORKS
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Interface.changeCards();
Interface.displayMessage("test of xyz");
} // 300
catch(Exception e){
e.printStackTrace();
} // 200
} // 400
// END OF UPDATEDATAFIELS END END END
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static JPanel frameForCardPane;
static CardLayout cardPane;
static JTextArea msgout;
TestQuestionPanel radio;
Interface () { // 100
super("This is a JFrame");
setSize(800, 400); // width, height
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// set-up card layout
cardPane = new CardLayout();
frameForCardPane = new JPanel(); // for CardLayout
frameForCardPane.setLayout(cardPane); // set the layout to cardPane = CardLayout
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frameForCardPane.add(cardTwo, "second");
// end set-up card layout
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pane.setLayout(new GridLayout(2, 4, 5, 15)); pane.setBorder(BorderFactory.createEmptyBorder(30, 20, 10, 30));
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pane.add( new JScrollPane(msgout));
pane.add(commandButtons);
msgout.append("Successful");
setContentPane(pane);
setVisible(true);
} // 100
// HERE ARE THE METHODS THAT SHOULD HANDLE THE UPDATING
static void changeCards() { // 200
cardPane.next(frameForCardPane);
System.out.println("Calling methods works!");
} // 200
static void displayMessage(String test) { // 200
String reset = "Test of reset.";
String passMessage = test;
cardPane.next(frameForCardPane);
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msgout.append("\n"+ test);
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} // 300Hi,
I instantiate it in this class. Does that change your opinion or the advice you gave me? Please help!
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class CardLayoutQuestionsv2 {
public static void main(String[] arguments) {
JFrame frame = new Interface();
frame.show();
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Thanks.
ChrisHere's a code snipet:
String dummy;
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case KeyEvent.VK_F1:
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Focus Problem with JTree and Menus
Hi all,
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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;
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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;
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JMenuBar bar = new JMenuBar();
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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;
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import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeCellEditor;
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extends DefaultTreeCellEditor
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private DefaultTreeModel m_model = null;
private JPanel m_display = null;
private JTextField m_field = null;
private JTree m_tree = null;
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m_model = (DefaultTreeModel) tree.getModel();
m_tree = tree;
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m_field = new JTextField();
m_display.add(new JLabel("My Label "));
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boolean expanded,
boolean leaf,
int row) {
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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:
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boolean expanded,
boolean leaf,
int row,
boolean hasFocus)
// Each node will be drawn as a check box
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Problem with addRow and MultiLine Cell renderer
Hi ,
Ive a problem with no solution to me .......
Ive seen in the forum and Ivent found an answer.......
The problem is this:
Ive a JTable with a custom model and I use a custom multiline cell renderer.
(becuse in the real application "way" hasnt static lenght)
When I add the first row all seem to be ok.....
when I try to add more row I obtain :
java.lang.ArrayIndexOutOfBoundsException: 1
at javax.swing.SizeSequence.insertEntries(SizeSequence.java:332)
at javax.swing.JTable.tableRowsInserted(JTable.java:2926)
at javax.swing.JTable.tableChanged(JTable.java:2858)
at javax.swing.table.AbstractTableModel.fireTableChanged(AbstractTableMo
del.java:280)
at javax.swing.table.AbstractTableModel.fireTableRowsInserted(AbstractTa
bleModel.java:215)
at TableDemo$MyTableModel.addRow(TableDemo.java:103)
at TableDemo$2.actionPerformed(TableDemo.java:256)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:17
64)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Abstra
ctButton.java:1817)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
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at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:257
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istener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5134)
at java.awt.Component.processEvent(Component.java:4931)
at java.awt.Container.processEvent(Container.java:1566)
at java.awt.Component.dispatchEventImpl(Component.java:3639)
at java.awt.Container.dispatchEventImpl(Container.java:1623)
at java.awt.Component.dispatchEvent(Component.java:3480)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3450
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3165)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3095)
at java.awt.Container.dispatchEventImpl(Container.java:1609)
at java.awt.Window.dispatchEventImpl(Window.java:1590)
at java.awt.Component.dispatchEvent(Component.java:3480)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:197)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
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This seems to be caused by
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About the model I think its ok.....but who knows :-(......
Please HELP me in anyway!!!
Example code :
import javax.swing.*;
import javax.swing.table.*;
import java.text.*;
import javax.swing.text.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class TableDemo extends JFrame {
private boolean DEBUG = true;
MyTableModel myModel = new MyTableModel();
MyTable table = new MyTable(myModel);
int i=0;
public TableDemo() {
super("TableDemo");
JButton bottone = new JButton("Aggiungi 1 elemento");
table.setPreferredScrollableViewportSize(new Dimension(500, 70));
//table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);
//Create the scroll pane and add the table to it.
JScrollPane scrollPane = new JScrollPane(table);
//Add the scroll pane to this window.
getContentPane().add(bottone,BorderLayout.NORTH);
getContentPane().add(scrollPane, BorderLayout.CENTER);
bottone.addActionListener(Add_Action);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
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MultiLineCellRenderer multiRenderer=new MultiLineCellRenderer();
MyTable(TableModel tm)
super(tm);
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if (col==1) return multiRenderer;
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class MyTableModel extends AbstractTableModel {
Vector data=new Vector();
final String[] columnNames = {"Name",
"Way",
"DeadLine (ms)"
public int getColumnCount() { return 3; }
public int getRowCount() { return data.size(); }
public Object getValueAt(int row, int col) {
Vector rowdata=(Vector)data.get(row);
return rowdata.get(col); }
public String getColumnName(int col) {
return columnNames[col];
public void setValueAt (Object value, int row,int col)
//setto i dati della modifica
Vector actrow=(Vector)data.get(row);
actrow.set(col,value);
this.fireTableCellUpdated(row,col);
public Class getColumnClass(int c)
return this.getValueAt(0,c).getClass();
public boolean isCellEditable(int row, int col) {
//Note that the data/cell address is constant,
//no matter where the cell appears onscreen.
if (col == 1)
return false;
else
return true;
public void addRow (String name,ArrayList path,Double dead) {
Vector row =new Vector();
row.add(name);
row.add(path);
row.add(dead);
row.add(name); //!!!Mi tengo questo dato da utilizzare come key per andare a
//prendere il path nella lista dei paths di Project
//(needed as key to retrive data if name in col. 1 is changed)
data.add(row);
//Inspector.inspect(this);
System.out.println ("Before firing Adding row...."+this.getRowCount());
this.fireTableRowsInserted(this.getRowCount(),this.getRowCount());
public void delRow (String namekey)
for (int i=0;i<this.getRowCount();i++)
if (namekey.equals(this.getValueAt(i,3)))
data.remove(i);
this.fireTableRowsDeleted(i,i);
//per uscire dal ciclo
i=this.getRowCount();
public void delAllRows()
int i;
int bound =this.getRowCount();
for (i=0;i<bound;i++)
{data.remove(0);
System.out.println ("Deleting .."+data);
this.fireTableRowsDeleted(0,i);
class MultiLineCellRenderer extends JTextArea implements TableCellRenderer {
private Hashtable rowHeights=new Hashtable();
public MultiLineCellRenderer() {
setEditable(false);
setLineWrap(true);
setWrapStyleWord(true);
//this.setBorder(new Border(
public Component getTableCellRendererComponent(JTable table,Object value, boolean isSelected, boolean hasFocus, int row, int column) {
//System.out.println ("Renderer called"+value.getClass());
if (value instanceof ArrayList) {
String way=new String (value.toString());
setText(way);
TableColumn thiscol=table.getColumn("Way");
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//setto il size della JTextarea sulle dimensioni della colonna
//per quanto riguarda il widht e su quelle ottenute da screen per l'height
this.setSize(thiscol.getPreferredWidth(),this.getPreferredSize().height);
// set the table's row height, if necessary
//System.out.println ("Valore getPreferred.height"+getPreferredSize().height);
if (table.getRowHeight(row)!=(this.getPreferredSize().height+2))
{System.out.println ("Setting Row :"+row);
System.out.println ("Dimension"+(getPreferredSize().height+2));
System.out.println ("There are "+table.getRowCount()+"rows in the table ");
if (row<table.getRowCount())
table.setRowHeight(row,(getPreferredSize().height+2));
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return this;
/**Custom JTextField Subclass che permette all'utente di immettere solo numeri
class WholeNumberField extends JTextField {
private Toolkit toolkit;
private NumberFormat integerFormatter;
public WholeNumberField(int value, int columns) {
super(columns);
toolkit = Toolkit.getDefaultToolkit();
integerFormatter = NumberFormat.getNumberInstance(Locale.US);
integerFormatter.setParseIntegerOnly(true);
setValue(value);
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int retVal = 0;
try {
retVal = integerFormatter.parse(getText()).intValue();
} catch (ParseException e) {
// This should never happen because insertString allows
// only properly formatted data to get in the field.
toolkit.beep();
return retVal;
public void setValue(int value) {
setText(integerFormatter.format(value));
protected Document createDefaultModel() {
return new WholeNumberDocument();
protected class WholeNumberDocument extends PlainDocument {
public void insertString(int offs,
String str,
AttributeSet a)
throws BadLocationException {
char[] source = str.toCharArray();
char[] result = new char[source.length];
int j = 0;
for (int i = 0; i < result.length; i++) {
if (Character.isDigit(source))
result[j++] = source[i];
else {
toolkit.beep();
System.err.println("insertString: " + source[i]);
super.insertString(offs, new String(result, 0, j), a);
ActionListener Add_Action = new ActionListener() {
public void actionPerformed (ActionEvent e)
System.out.println ("Adding");
ArrayList way =new ArrayList();
way.add(new String("Uno"));
way.add(new String("Due"));
way.add(new String("Tre"));
way.add(new String("Quattro"));
myModel.addRow(new String("Nome"+i++),way,new Double(0));
public static void main(String[] args) {
TableDemo frame = new TableDemo();
frame.pack();
frame.setVisible(true);In the addRow method, change the line
this.fireTableRowsInserted(this.getRowCount(),this.getRowCount()); to
this.fireTableRowsInserted(data.size() - 1, data.size() - 1);Sai Pullabhotla -
Hai to all,
I am having a problem with GUI in applets
My first class extends a JPanel named A_a
import javax.swing .*;
import java.awt.*;
import java.awt.event.*;
public class A_a extends JPanel
JButton jb;
JTextArea text;
public A_a()
setLayout(new FlowLayout());
jb=new JButton("Click me");
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text=new JTextArea(5,20);
add(text);
public void text_appendText(String aa)
System.out.println("I AM IN A_a");
text.append(aa);
text.revalidate();
revalidate();
/*public static void main(String ags[])
A_a a = new A_a();
JFrame frame=new JFrame();
frame.getContentPane().add(a);
frame.pack();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) { System.exit(0); }
frame.setSize(200,200);
frame.show();
and then I am using other class B_b which is an applet carries a exitsing panel (A_a) inside it .
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class B_b extends JApplet
public A_a a;
public void init()
a=new A_a();
getContentPane().add(a);
public void text_appendText(String aa)
final String aaa =aa;
new Thread(new Runnable()
public void run()
a=new A_a();
a.setBackground(new java.awt.Color(255,200,200));
System.out.println("I AM IN B_b");
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a.text.revalidate();
getContentPane().remove(a);
resize(500,500);
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import javax.swing .*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;
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JTextArea jta;
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jbt=new JButton("Click me");
jbt.addActionListener(this);
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Applet applets = null;
while(e.hasMoreElements())
applets=(Applet)e.nextElement();
if ( applets instanceof B_b)
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((B_b)applets).remove());
((B_b)applets).getContentPane().add(D_d);
both the applets C_c and B_b are in same browser page
How can i achive that pls help .Just to make the code readable...
import javax.swing .*;
import java.awt.*;
import java.awt.event.*;
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JButton jb;
JTextArea text;
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setLayout(new FlowLayout());
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add(text);
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text.append(aa);
text.revalidate();
revalidate();
/*public static void main(String ags[])
A_a a = new A_a();
JFrame frame=new JFrame();
frame.getContentPane().add(a);
frame.pack();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) { System.exit(0); }
frame.setSize(200,200);
frame.show();
}and then I am using other class B_b which is an applet carries a exitsing panel (A_a) inside it .
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class B_b extends JApplet
public A_a a;
public void init()
a=new A_a();
getContentPane().add(a);
public void text_appendText(String aa)
final String aaa =aa;
new Thread(new Runnable()
public void run()
a=new A_a();
a.setBackground(new java.awt.Color(255,200,200));
System.out.println("I AM IN B_b");
a.text.append(aaa);
a.text.revalidate();
getContentPane().remove(a);
resize(500,500);
}).start();
}and the I am using the second applet C_c in which by performing a button action the old panel A_a should get removed and replace the new panel D_a (which is not here )in the applet B_b with all other components(namely button , text fields etc)
import javax.swing .*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;
public class C_c extends JApplet implements ActionListener
JButton jbt;
JTextArea jta;
public void init()
getContentPane().setLayout(new FlowLayout());
jbt=new JButton("Click me");
jbt.addActionListener(this);
getContentPane().add(jbt);
jta=new JTextArea(5,20);
getContentPane().add(jta);
public void actionPerformed(ActionEvent ae)
Enumeration e = getAppletContext().getApplets();
Applet applets = null;
while(e.hasMoreElements())
applets=(Applet)e.nextElement();
if ( applets instanceof B_b)
System.out.println("I AM CLASS C_c");
((B_b)applets).text_appendText(jta.getText());
((B_b)applets).remove());
((B_b)applets).getContentPane().add(D_d);
} -
Problem with Applets in same page
Hai to all,
I am having a problem with GUI in applets
My first class extends a JPanel named A_a
import javax.swing .*;
import java.awt.*;
import java.awt.event.*;
public class A_a extends JPanel
JButton jb;
JTextArea text;
public A_a()
setLayout(new FlowLayout());
jb=new JButton("Click me");
//add(jb);
text=new JTextArea(5,20);
add(text);
public void text_appendText(String aa)
System.out.println("I AM IN A_a");
text.append(aa);
text.revalidate();
revalidate();
/*public static void main(String ags[])
A_a a = new A_a();
JFrame frame=new JFrame();
frame.getContentPane().add(a);
frame.pack();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) { System.exit(0); }
frame.setSize(200,200);
frame.show();
and then I am using other class B_b which is an applet carries a exitsing panel (A_a) inside it .
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class B_b extends JApplet
public A_a a;
public void init()
a=new A_a();
getContentPane().add(a);
public void text_appendText(String aa)
final String aaa =aa;
new Thread(new Runnable()
public void run()
a=new A_a();
a.setBackground(new java.awt.Color(255,200,200));
System.out.println("I AM IN B_b");
a.text.append(aaa);
a.text.revalidate();
getContentPane().remove(a);
resize(500,500);
}).start();
and the I am using the second applet C_c in which by performing a button action the old panel A_a should get removed and replace the new panel D_a (which is not here )in the applet B_b with all other components(namely button , text fields etc)
import javax.swing .*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;
public class C_c extends JApplet implements ActionListener
JButton jbt;
JTextArea jta;
public void init()
getContentPane().setLayout(new FlowLayout());
jbt=new JButton("Click me");
jbt.addActionListener(this);
getContentPane().add(jbt);
jta=new JTextArea(5,20);
getContentPane().add(jta);
public void actionPerformed(ActionEvent ae)
Enumeration e = getAppletContext().getApplets();
Applet applets = null;
while(e.hasMoreElements())
applets=(Applet)e.nextElement();
if ( applets instanceof B_b)
System.out.println("I AM CLASS C_c");
((B_b)applets).text_appendText(jta.getText());
((B_b)applets).remove());
((B_b)applets).getContentPane().add(D_d);
both the applets C_c and B_b are in same browser page
How can i achive that pls help .please help me its urgent for my project
-
Problem with Background image and JFrame
Hi there!
I've the following problem:
I created a JFrame with an integrated JPanel. In this JFrame I display a background image. Therefore I've used my own contentPane:
public class MContentPane extends JComponent{
private Image backgroundImage = null;
public MContentPane() {
super();
* Returns the background image
* @return Background image
public Image getBackgroundImage() {
return backgroundImage;
* Sets the background image
* @param backgroundImage Background image
public void setBackgroundImage(Image backgroundImage) {
this.backgroundImage = backgroundImage;
* Overrides the painting to display a background image
protected void paintComponent(Graphics g) {
if (isOpaque()) {
g.setColor(getBackground());
g.fillRect(0, 0, getWidth(), getHeight());
if (backgroundImage != null) {
g.drawImage(backgroundImage,0,0,this);
super.paintComponent(g);
Now the background image displays correct. But as soon as I click on some combobox that is placed within the integrated JPanel I see fractals of the opened combobox on the background. When I minimize
the Frame they disappear. Sometimes though I get also some fractals when resizing the JFrame.
It seems there is some problem with the redrawing of the background e.g. it doesn't get redrawn as often as it should be!?
Could anyone give me some hint, on how to achieve a clear background after clicking some combobox?
Thx in advanceI still prefer using a border to draw a background image:
import java.awt.*;
import java.awt.image.*;
import javax.swing.border.*;
public class CentredBackgroundBorder implements Border {
private final BufferedImage image;
public CentredBackgroundBorder(BufferedImage image) {
this.image = image;
public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
int x0 = x + (width-image.getWidth())/2;
int y0 = y + (height-image.getHeight())/2;
g. drawImage(image, x0, y0, null);
public Insets getBorderInsets(Component c) {
return new Insets(0,0,0,0);
public boolean isBorderOpaque() {
return true;
}And here is a demo where I load the background image asynchronously, so that I can launch the GUI before the image is done loading. Warning: you may find the image disturbing...
import java.awt.*;
import java.io.*;
import java.net.URL;
import javax.imageio.*;
import javax.swing.*;
import javax.swing.border.*;
public class BackgroundBorderExample {
public static void main(String[] args) throws IOException {
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame f = new JFrame("BackgroundBorderExample");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JTextArea area = new JTextArea(24,80);
area.setForeground(Color.WHITE);
area.setOpaque(false);
area.read(new FileReader(new File("BackgroundBorderExample.java")), null);
final JScrollPane sp = new JScrollPane(area);
sp.setBackground(Color.BLACK);
sp.getViewport().setOpaque(false);
f.getContentPane().add(sp);
f.setSize(600,400);
f.setLocationRelativeTo(null);
f.setVisible(true);
String url = "http://today.java.net/jag/bio/JagHeadshot.jpg";
final Border bkgrnd = new CentredBackgroundBorder(ImageIO.read(new URL(url)));
Runnable r = new Runnable() {
public void run() {
sp.setViewportBorder(bkgrnd);
sp.repaint();
SwingUtilities.invokeLater(r);
} -
Problem with display of JScrollPane
I have made a small GUI.
It has a JFrame and four JPanels are added to the frame.
The placement is done by program and hence layout manager is set to null.
Two of the panels contain JScrollPane.
One scroll pane is associated with a JList.
Another scroll pane is associated with a JTextArea.
I am creating panel components in their respective paintComponent() method.
Now my problem is whenever I run the code, the behaviour of the display of the GUI is erratic. Sometimes it appears perfectly fine other times the JList contents and JTextArea along with their scroll bars don't appear. I have tried running the code on different platforms and different systems. On some systems it works perfectly fine, on some it behaves erratically.
Moreover my experience is that it is giving problem on somewhat lower configuration systems (low RAM and CPU) and running fine on higher configuration systems.
I ran it on my laptop with 512MB RAM and centrino duo processor. (Both on windows and ubuntu it gave the same problem, random display behavior)
I ran it on a desktop with 1GB RAM and higher processor (Both on windows and ubuntu it displayed fine)
Does this problem relate to insufficient painting time or something of this sort? Why is this problem is coming and what's the solution?
Thanks in advance.
Also if anybody has encountered similar problem please do share so that I could at least say this is not a unique one.The placement is done by program and hence layout manager is set to null.That is (probably) your first problem. Learn to use use LayoutMangers, they save time in the long run.
Sometimes it appears perfectly fine other times the JList contents and JTextArea along with their scroll bars don't appearProbably because preferred sizes are not set correctly. Since you are not using a layout manager that is your responsibility. Easy solution is to use a proper combination of layout managers.
I am creating panel components in their respective paintComponent() method.That is (probably) your second problem. paintComponent() is for doing custom painting, not creating new components dynamically.
I suggest you start by reading the Swing tutorial for example programs. -
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.
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