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Can't edit any component in GUI

I came up with a recently problem that, any component that I add to a JPanel (JTextField, JTextArea, JTable) can't edit even when I force it, in code, to be enabled and editable. I'm using NetBeans for developing the project.
Anyone here faced this problem? Looks like I'll be forced to change all to JFrame. Even though, hope that someone reply this topic with some constructive idea/help.

Try to call setFocusable(true) for the top level container.

I have two reasons/opinions/thoughts as to why you are getting "errors".
You aren't adding the components to the panel correctly.
panel.add(someComponent);
panel.add(anotherComponent);
panel.add(yetAnotherComponent);
frame.add(panel);
You are overriding the default behavior for the components. All components in a JFrame, JWindow, etc. are by default enabled and editable (meaning there is an implied setEnabled(true) and setEditable(true), respectively).

Swing: Is there a simple way to make 1 component ignore the layout manager?

I have a JPanel with one component that I want to place in an absolute sense, whereas the rest of the components are placed according to a layout manager.
Is there a simple way to do this?

Are you saying you want a component painted over top of all the other components? If so then you would need to use a JLayeredPane.
Why don't you post a SSCCE that demonstrates what you want to do?
You can add components to a frame as you would do normally and make the frame visible. Then you can add this random component and use setBounds on the component. As long as you don't revalidate() the panel or resize the frame we will be able to see how you intend to position this component relative to all the other components.

You might also want to look at OverlayLayout, seen here. For some reason it's excluded from the conventional gallery, but it may be of interest.

You can do this with only needing one JPanel using MigLayout

Prevent Java from repainting the content of a JPanel while updating

I have a JPanel which contains a lot of child components. While updating\adding new components to the parent JPanel I'd like to prevent it from repainting, how can this achieved?

Try RepaintManager.currentManager(component).markCompletelyClean(component). It will prevent the component from repainting. You might need to do this after each time you add new components.

setVisible(false)
update
setVisible(true)

you could try by using setIgnoreRepaint(boolean value) but it's a typical swing feature that can or cannot work (mainly because it depends from AWT so you never know).
Otherwise you could override the paint method by using a flag that simply makes the methor return without calling super.paint(). (actually overriding paintComponent should be the right choice)

Question to pack() method

I'm building a GUI application, and within a JFrame i have 2 jcombobox's and a JPanel to view certain data. Now when i call the pack() methode in the main class it puts the two jcombobox'es next to my JPanel, which i dont want, because I want them North. Ofcourse I've tried to hard-code it in my code, but it doesn't work after I've called the pack() method.
Are there any alternatives to this method?

Only one component can be NORTH, so if you want both ComboBoxes to be NORTH you have to add them into a separate container. This separate container can then be put NORTH.
(Post the source for more exact help.)

All pack does is resize the Window (in this case JFrame) to its preferred size and the preferred sizes of its sub-components. To control the actual location of the sub-components relative to one another you need to use an appropriate LayoutManager.
You might want to check out the Using Layout Managers tutorial.

The pack() method just causes the layouting to happen, it has abolutely nothing to do with what is put where.
Most likely you're not using layout managers correctly. Show us your code and we can tell you waht exactly you're doing wrong.

You can avoid using pack by explicitly setting the frame size with setSize and setBounds. However, using pack is usually the preferred way as it leaves the frame layout manager in charge of the frame size.
That being said, the problem you are describing appears to be related to the correct use of a layout manager rather than the sizing of the frame. Have a look at the various layout managers for Swing and how to use them: http://download.oracle.com/docs/cd/E17409_01/javase/tutorial/uiswing/layout/using.html.

Best way of subclassing a JPanel in Swing

I am currently trying to build an expanding panel in Swing (akin the WPF's Expander control) and I'd like to retain the usual methods for manipulating it (i. e. setLayout, add, etc.). Only they should be routed to an embedded panel (the one being shown or hidden).
How would one do that? Overriding every method of JComponent and re-routing that to an embedded JPanel would be cumbersome, but that's the only way I see.
Or should I rather make the embedded panel visible to the outside and force users to use something like ExpanderPanel.getInnerPanel() instead. But then it's no drop-in replacement for JPanel which I think would be nice to have.

Take a look at the JXTaskPane from Swingx project. It already does what you need.

In 1.5(ish) Swing routed a few methods to the content pane in JFrame, JApplet, etc. Whilst there appeared to be some usability benefits for those just starting, it doesn't actually fix the problem. So everyone has to deal with a very strangely behaving API. So my advice is to avoid this approach.

If you have a Container widget which holds a panel you want to show and hide, why not layout your inner panel however you want, then add it to the Container panel, then use static methods against the Container to say
JPanel p = new JPanel();
//do something with the JPanel...
ContainerWidget.setContent(p);
ContainerWidget.expandPanel(p,true);
Would somethign like this work?