Develop Reference

external panels in swing

I have something like this...
Its a bunch of JLabels within JPanels inside a
--JFrame
--JPanel
--Set<JPanel>
--JLabel object contained in each JPanel object cotained in the set
I want to create an external panel/frame so that each time I hover over each individual JPanel, a new frame/panel pops up giving me some data. This will essentially overlap over the JFrame.
Its pretty brief but I just need some guidance as to what I need to look up.

Maybe you can just use JToolTip. When the mouse hovers over the label for a couple of seconds it will display automatically. See the section from the Swing tutorial on How to Use Tool Tips.
Or if you want something more complicated use a MouseListener. On mouseEntered() you can display a JPopupMenu or an undecorated JDialog.
You can start by reading the Swing tutorial on How to Write a Mouse Listener.

JPanel data getting changed on mouse click

I am using three JButtons in my swing application. When I click on each button, the corresponding data (formatted in JTable with JScrollPane) will display on JPanel.
Problem: when I resize the JFrame, the JPanel is replacing with default button (the button which i was clicked first) information instead of current JButton information.
My sample code:
jbutton1.addActionListener(this);
jbutton2.addActionListener(this);
public void actioPerformed(ActionEvent e){
if(e.getActionCommand.equals("button1"))
JPanel.add(table1);
}
if(e.getActionCommand.equals("button2"))
JPanel.add(table1);
}.......

Resizing the JPanel will not suddenly replace components or add other components to the panel.
My best guess (and it is a guess due to the limited information in the question) is that none of your buttons actually work and just show the wrong information.
The code you posted only contains an add without any revalidation of the layout. Consult the javadoc of the Container#add method. When you resize, the layout gets revalidated and you see what is actually contained in the JPanel.
Possible solutions:
Call invalidate and repaint on your panel as well in your ActionListener
Use a CardLayout to switch between the different components
I personally prefer the CardLayout option, but it might depend a bit on the situation.
Note that in the code you posted, you add table1 for both buttons. Might be a copy-paste problem, or a problem with your actual code.

I was unable express problem clearly.Sorry for your inconvenience.
JPanel.removeAll() method has fixed my problem.
I added this method before adding any new component to JPanel. That fixes JPanel unexpected behavior.

Java JFrame displaying initialisation content when losing focus

My application uses the BorderLayout to display content in the frame. I also have a menubar at the top so other frames can be toggled to show. When I launch the application, each of these content areas of the frame are given a JPanel with the centre loaded with a 'startup screen' and once some background initialisation has been completed, the panel is then change to start displaying information post-initialisation. This panel is then updated 5 times every second, controlled by a loop.
When I select the menubar the display of the centre panel reverts back to that of startup screen. When I deselect the menubar the panel reverts to that of the correct one to be displayed. Debugging this leads to the entire Eclipse environment crashing.
Does anyone know what may be causing this? I'm not sure what code to show here so if you require more information I will edit this as such.

1.have look at Initial Thread, be sure that GUI is created especially visible wrapped into invokeLater()
2.last code lines in the Swing GUI constructor would be
code
myFrame.pack();
myFrame.setVisible(true);
}
3.for better help sooner post an SSCCE

Refreshing the JPanel or Closing and Opening Again

I'm writing a simple slide program. In that program, I show small thumbnails of all slides in a new jpanel. In that new jpanel, after clicking 2 thumbnails, it should swap them. However, after swaping them, jpanel is not refreshing. If I create new jpanel by calling createAndShowGUI() function, it is ok, but then I need to close the old jpanel.
Below is my simple class,
http://docs.oracle.com/javase/tutorial/uiswing/examples/layout/GridLayoutDemoProject/src/layout/GridLayoutDemo.java
And in my main program if I click "slide sorter mode" button handler compile the following code
gridLayoutDemoObject.createAndShowGUI();
What is the solution and how should I make it ?
Thanks.

You didn't provide enough information to indicate how you display the images or how you swap them so its hard to give a proper answer.
I would display the images by using a JLabel (or JButton without a Border). Then when you can just use setIcon(...) to swap icons and the label will repaint itself.
Next time post an SSCCE that demonstrates the problem so we don't have to guess what you are talking about.

JComboBox drop down show problem

I am developing an applet, and use some panels, which according to some situations some panels are shown or hidden. in one panel I have a JComboBox which I fill them at runtime. my problem is when I show this panel, the JComboBox is filled, and enabled, but I cannot drop it down. I tested it on a simple applet, but it was correct, but I don't know why it does not show in my applet.
Please help me.
Thanks.

WAG - don't mix Swing with AWT.