Develop Reference

Create Custom Look and Feel for a JTabbedPane

I am trying to create a JTabbedPane that will always fill the top part of the Component with the tabs. Like so:
And this is how it look now:
And the code for this part:
JTabbedPane tab = new JTabbedPane();
tab.addTab("Items", items);
tab.addTab("Categories", categories);
setContentPane(tab);
//Also tried to create a JTabbedPane class and see if i could remove the labels and manually add two buttons to the top but without success.
I want the tabs to use up as much space as possible without actually shrinking the content of the panels.
So could anyone tell me how to customize the JTabbedPane, the look and feed or just the tabs themselves in order to do that.

The easiest approach is probably to create your own component:
Create a "main" panel that uses a BorderLayout.
Create a panel that uses a GridLayout and add your buttons to this panel. Then add this panel to the "main" panel using BorderLayout.PAGE_START. Each of these button will display a specific panel when clicked.
Create a second panel that uses a CardLayout. Add this panel to the "main" panel using BorderLayout.CENTER. Each of these panels will represent a tab.
The other option is to look at the TabbedPaneUI and find a method that paints each tab and modify the code for your requirement.

JFrame with panel count depending from parameter

I am creating simple application in java - Eclipse - WindowBuilder Editor. JFrame`s contentPane has JGoodies FormLayout in which I have to place 3 or 4 Panels - depending on mode.
It is proper way to make if construction that decides if content pane will be divided 1x3 or 1x4(facilitation because between all I use relatedgaps and so on..)?
I am not sure if this is good approach but I do not know how can I do this in other way than if construction. It has to be practical and flexible approach - to handle resizing the window, et cetera..

Common approaches for dynamic layout include these:
Use revalidate(), and possibly repaint(), to layout a Container again after adding or removing components, as shown here.
Replace the layout and validate() the Container, as shown here.
Use CardLayout to replace one panel with another, as shown here and here.

Swing containers within containers

I am somewhat new to the whole java swing scene, and I just want some clarifications due to a slight confusion I have. I have learned about orientation and buttons and all the basics. Also pointing to some good (non oracle) tutorials will be highly appreciated.
As far as I understand, we have our JFrame which is a window.
Then our JFrame consists of ContentPane, which I am using a container for.
Container content = frame.getContentPane();
Now that I have this container, can I add more containers within those containers? Let's say that I would like to have different parts that do different things, and for that I would like to create classes and such that each handle their own containers?
So what I am asking for is, how does one go about storing different content within the container? What is the proper way to go about it?
An example I would give is let's say I have a scoreboard (for soccer) that is on the top part of the window, on the middle part of the window there is some work related business stuff, and on the bottom part of the window I have some textbox that does its thing with a few buttons.
Sorry if this question is stupid, I am just trying to learning swing, and want to know proper way to arrange different components within the window.

Yes, you can. Create an instance of JPanel and add your components to it, and then add them to the frame's content pane using a string:
JPanel panel = new JPanel();
//code to add stuff to the panel
frame.getContentPane().add("Center", panel); //"North", "South", "East", "West", or "Center"

JTabbedPane doesn't work correctly

public void tabbedPane(){
JPanel tab1 = new JPanel();
JButton btn = new JButton("Buton - 1");
btn.setPreferredSize(new Dimension(50, 20));
btn.setLocation(0, 10);
tab1.add(btn);
JTabbedPane tabPanel = new JTabbedPane();
tabPanel.addTab("tab1", null, tab1);
tabPanel.addTab("tab2", tab1);
tabPanel.addTab("tab3", btn);
tabPanel.setPreferredSize(new Dimension(450, 150));
tabPanel.setLocation(50, 0);
mainPanel.add(tabPanel);//Main panel on frame
}
When I run my application, I see only tab2 and tab3 pane, and I have many issues:
tabPanel.setLocation doesn't work
tabPanel.addTab("tab1" ...) doesn't work
btn.setPreferredSize(new Dimension(50, 20)); when I
click "tab2" it works correctly, however when I click "tab3" it doesn't change button
size.. why?
and i use null layout

tabPanel.setLocation doesn't work
Don't use setLocation(...) but instead use nested components and layout managers to achieve a pleasing and easy to maintain GUI layout.
tabPanel.addTab("tab1" ...) doesn't work
With Swing, you can only add a component to one container, that's it. The component will only show up in the last container that it was added to.
btn.setPreferredSize(new Dimension(50, 20)); when I click "tab2" it works correctly, however when I click "tab3" it doesn't change button size.. why?
Again, you will want to study the layout managers
and i use null layout
You almost never want to do this as this will make your application not look correct on any platform but your own and will make it very very difficult to maintain and upgrade. It is much better to use the layout managers and let them do the heavy lifting of laying out and sizing components for you.

What is your objective with this?
A JTabbedPane is used to organize views, I see you're trying to add a JPanel as a first tab, this is the 'main goal' of the JTabbedPanes.
tabPanel.addTab("Tab 1", tab1);
Try to add the tab like this, you're passing a 'null' value as the icon, which must not affect at all, but if you're not using an icon, then just add the panel as a tab with the intended name.
On second adding, you're adding again the same component (tab1).
On third adding, you're trying to add a component already on a container (tab1). This will make this component to appear only in the last container you add it to. Besides, component is a JButton. I cannot see the goal of a JButton as a tab.
For the setLocation(x, y) issue, check the layout you're using on the container.
Again, I think the main issue here is that you're not correctly approaching your problem, or you're not using the required tools.

Java Swing resizing UI overlap elements

I have created a GUI with NetBeans GUI Builder and manually wrote some additional code.
I don't really know how to properly describe this problem, so please have a look at the picture below.
This is a default view, where you can notice the JTable that has been created inside a JPanel manually:
jPanel1.setLayout(new BorderLayout());
TableModel model = db.populateJTable();
JTable jTable1 = new JTable(model);
jTable1.setModel(model);
JScrollPane tableContainer = new JScrollPane(jTable1);
jPanel1.add(tableContainer);
View.super.getContentPane().add(jPanel1);
//View.super.pack();
View.super.setVisible(true);
When I try to resize the window horizontally, all components react properly by resizing as specified, but the JTable just stay where rendered before, overlapping with other elements:
Can someone please tell me what is happening and how should I proceed?
many thanks

A powerful solution: use Layouts. They do all the job for you while resizing.
A good one is GridBagLayout. If you need more complex layout, you can use the powerful BoxLayout
That if you want to design your layout manually. For me, I prefer using NetBeans 7.2.1 designer. It automatically configures the layout for you while designing them in the design window.