How to Center Jpanel in JFrame?

Question

There is a class which extends JFrame. then Further JFrame have JPanel named contentPane and this Jpanel contains 2 more jpanel. as Tree shown in picture.

Here is the Image

I Want to Center that contentPane in JFrame so that on changing size of JFrame JPanel (contentPane) will remain in center. I have tried with different Layouts but did not come up with right one. is there any way ? Full page picture is here

Code is this.

public class Purchases extends JFrame {

    private JPanel contentPane;

public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Purchases frame = new Purchases();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }); 
    }


        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 513, 438);


        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);
        setLocationRelativeTo(null);



        JPanel panel = new JPanel();
        panel.setBounds(10, 10, 477, 193);
        contentPane.add(panel);
        panel.setLayout(null);

        JPanel panel_1 = new JPanel();
        panel_1.setBounds(10, 214, 477, 174);
        contentPane.add(panel_1);
        panel_1.setLayout(null);

}

This code is Eclipse automatically generated. I did not find where the contentPane is added in JFrame.

do you just want to center the panel, so that on resize ( jframe gets bigger) there is a empty border on all sides ? this seems a bit unnatural to me — Wagner Michael, Jan 25 '15 at 10:25
if there is empty borders i will increase the size of JPanel. porblem is to center. size i will handle — Adnan Ali, Jan 25 '15 at 10:28
Add the panel as a single component to a `GridBagLayout` that will center it. E.G. as seen in [this answer](http://stackoverflow.com/a/9090772/418556). — Andrew Thompson, Jan 25 '15 at 10:30
Personally, set the frame's content pane to `GridBagLayout`, then wrap your existing content to another `JPanel` and then add this to the frame. — MadProgrammer, Jan 25 '15 at 10:49
@Andrew that code have 4 different things i need only one. I am Trying let me check if it helps — Adnan Ali, Jan 25 '15 at 10:54
@MadProgrammer can i get a sample. or u can explain it more ? — Adnan Ali, Jan 25 '15 at 10:55
For [example](http://stackoverflow.com/questions/21058565/how-to-center-jpanel-when-jframe-is-resized-or-maximized/21058902#21058902) — MadProgrammer, Jan 25 '15 at 10:55
@MadProgrammer form that code i got, I have to add one more panel ? I am right? let me try it. — Adnan Ali, Jan 25 '15 at 11:00

score 3 · Answer 1 · edited May 23 '17 at 12:09

Set the frame's layout to GridBagLayout. Wrap your existing content in another JPanel, add this panel to the frame

For example

Take a look at Laying Out Components Within a Container and How to Use GridBagLayout for more details

You really should avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify

score 1 · Answer 2 · answered Jul 27 '17 at 11:01

I have made a sample for you. Modify it as per your need. Just want to show you what you want, is working.

    TestClass()
    {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 513, 438);

        contentPane = new JPanel();
        contentPane.setLayout(new BorderLayout());

        JButton b1 = new JButton("hello");
        JPanel panel = new JPanel(new BorderLayout());
        //panel.setBounds(10, 10, 477, 193);
        panel.add(b1, BorderLayout.CENTER);
        contentPane.add(panel, BorderLayout.EAST);
        //panel.setLayout(null);

        JButton b2 = new JButton("why");
        JPanel panel_1 = new JPanel(new BorderLayout());
        //panel_1.setBounds(10, 214, 477, 174);
        panel_1.add(b2, BorderLayout.CENTER);
        contentPane.add(panel_1, BorderLayout.WEST);
        //panel_1.setLayout(null);

        this.getContentPane().add(contentPane);
    }

Hope this will help. :-)

score -1 · Answer 3 · edited May 23 '17 at 12:17

-1

I think you should set the maximum size of the element & set it to align center:

setAlignmentX(JComponent.CENTER_ALIGNMENT);
setMaximumSize(new Dimension(100, 100));

As explained here: How can I properly center a JPanel ( FIXED SIZE ) inside a JFrame?

edited May 23 '17 at 12:17

Community

1
1

answered Jan 25 '15 at 10:24

RonM

187
3

let me see if it helps – Adnan Ali Jan 25 '15 at 10:30
See [Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?](http://stackoverflow.com/q/7229226/418556) (Yes.) – Andrew Thompson Jan 25 '15 at 10:30
And if you remove the MaximumSize(), it doesn't center it? – RonM Jan 25 '15 at 10:51
its already not in center so what to do with maximumSize. actually that code is IDE generated. if i could understand that i have done it :@ – Adnan Ali Jan 25 '15 at 10:57

How to Center Jpanel in JFrame?

3 Answers3