What's the best way to keep JButtons centered in a JPanel using GroupLayout on JPanel resize

Question

I originally spent quite a bit of time trying to get the JPanel to re-size when the dialog gets re-sized by grabbing the bottom right corner with the mouse and dragging. I cracked that, I think, but now cannot get the buttons to stay centered. I've included some stripped down code, and I pulled out the other panels (I use the JLayeredPane because there are 5 panels not just the one shown). I saw a fix for this if I was using a JLabel elsewhere on StackOverFlow, but haven't been able to crack this yet. Any help would be appreciated. It seems like I must be missing something really simple. This is my first post so I hope you'll bear with any formatting errors. Thanks....

import java.awt.Color;
import java.awt.Component;
import java.util.logging.Logger;

import javax.swing.GroupLayout;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class mock2Dialog extends JDialog {


private static final long serialVersionUID = 1L;
public static int BUTTON_UNKNOWN = -1;
public static int BUTTON_NO = 1;
public static int BUTTON_YES = 0;

public static int DIALOG_TYPE_YES_NO = 1;

int buttonClicked = BUTTON_UNKNOWN;
int dialogType = 1;
Logger logger = null;

public mock2Dialog() {
    }

public mock2Dialog(java.awt.Frame parent, boolean modal, String title,
        int dialogType, Logger logger) {
    super(parent, modal);
    this.logger = logger;
    this.dialogType = dialogType;
    initComponents(); 
    this.setTitle(title);
    buttonClicked = BUTTON_UNKNOWN;

    getYesButton().setFocusTraversalKeysEnabled(false);
    getNoButton().setFocusTraversalKeysEnabled(false);

    getYesNoPanel().setVisible(false);

    getYesButton().setVisible(false);
    getNoButton().setVisible(false);

    onOpen(this); //this fakes out the system so I can execute from this file       

}//EOM

public void onOpen(Component caller) {
    setLocationRelativeTo(caller);
    prepareOnOpen();
}//EOM

public void prepareOnOpen() {
    getYesNoPanel().setVisible(false);
    getYesButton().setVisible(false);
    getNoButton().setVisible(false);

    if (dialogType == DIALOG_TYPE_YES_NO) {
        getYesNoPanel().setVisible(true);
        getYesButton().setVisible(true);
        getNoButton().setVisible(true);
    } 

    buttonClicked = BUTTON_UNKNOWN;
    if (dialogType == DIALOG_TYPE_YES_NO) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                yesButton.requestFocusInWindow();
            }
        });

    }
    this.setVisible(true);
} //EOM


private void initComponents() {

    msgScrollPane = new JScrollPane();
    msgTextArea = new JTextArea();
    jLayeredPane1 = new JLayeredPane(); //no LayoutManager specified by design of component
    yesNoPanel = new JPanel();
    yesButton = new JButton();
    noButton = new JButton();


    setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
    setTitle("Message");

    //msgScrollPane
    msgScrollPane.setBorder(null);

    //msgTextArea
    msgTextArea.setColumns(20);
    msgTextArea.setEditable(false);
    msgTextArea.setFont(new java.awt.Font("Verdana", 0, 14));
    msgTextArea.setRows(5);
    msgTextArea.setWrapStyleWord(true);
    msgTextArea.setBorder(javax.swing.BorderFactory.createEtchedBorder());
    msgTextArea.setOpaque(false);
    msgScrollPane.setViewportView(msgTextArea);

    //YesNoPanel
    yesNoPanel.setBackground(Color.BLUE);
    yesButton.setText("Yes");
    yesButton.setName("yesButton");
    //yesButton.setAlignmentX(CENTER_ALIGNMENT); //thought this might work to center the button within the panel

    noButton.setText("No");
    noButton.setName("noButton");
    //noButton.setAlignmentX(CENTER_ALIGNMENT); //thought this might work to center the button within the panel

    GroupLayout yesNoPanelLayout = new GroupLayout(
            yesNoPanel);
    yesNoPanel.setLayout(yesNoPanelLayout);
    yesNoPanelLayout
            .setHorizontalGroup(yesNoPanelLayout
                    .createParallelGroup(
                            javax.swing.GroupLayout.Alignment.LEADING) //Center doesn't seem to change behaviour
                    .addGroup(
                            yesNoPanelLayout
                                    .createSequentialGroup()
                                    .addGap(146, 146, 146)
                                    .addComponent(yesButton)
                                    .addPreferredGap(
                                            javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(noButton)
                                    .addContainerGap(147, Short.MAX_VALUE)));
    yesNoPanelLayout
            .setVerticalGroup(yesNoPanelLayout
                    .createParallelGroup(
                            javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(
                            yesNoPanelLayout
                                    .createSequentialGroup()
                                    .addContainerGap()
                                    .addGroup(
                                            yesNoPanelLayout
                                                    .createParallelGroup(
                                                            javax.swing.GroupLayout.Alignment.LEADING)
                                                    .addComponent(yesButton)
                                                    .addComponent(noButton))
                                    .addContainerGap(
                                            javax.swing.GroupLayout.DEFAULT_SIZE,
                                            Short.MAX_VALUE)));

    yesNoPanel.setBounds(0, 0, Short.MAX_VALUE, 50); //setting Short.MAX_VALUE will allow the panel to expand.
    jLayeredPane1.add(yesNoPanel, javax.swing.JLayeredPane.DEFAULT_LAYER);


    //main layout for the dialog
    GroupLayout layout = new GroupLayout(
            getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(layout
            .createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGroup(
                    layout.createSequentialGroup()
                            .addComponent(jLayeredPane1,
                                    GroupLayout.DEFAULT_SIZE,
                                    GroupLayout.DEFAULT_SIZE, //400,
                                    Short.MAX_VALUE)
                            .addGap(0, 0, 0))
            .addGroup(
                    layout.createSequentialGroup()
                            .addGap(12, 12, 12)
                            .addComponent(msgScrollPane,
                                    GroupLayout.DEFAULT_SIZE,
                                    376, 
                                    Short.MAX_VALUE).addContainerGap()));
    layout.setVerticalGroup(layout
            .createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGroup(
                    GroupLayout.Alignment.TRAILING,
                    layout.createSequentialGroup()
                            .addContainerGap()
                            .addComponent(msgScrollPane,
                                    GroupLayout.DEFAULT_SIZE,
                                    106, Short.MAX_VALUE)
                            .addPreferredGap(
                                    javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(jLayeredPane1,
                                    GroupLayout.PREFERRED_SIZE,
                                    50,
                                    GroupLayout.PREFERRED_SIZE)));

    pack();
} 

private JLayeredPane jLayeredPane1;
private JScrollPane msgScrollPane;
private JTextArea msgTextArea;
private JButton noButton;
private JButton yesButton;
private JPanel yesNoPanel;

public javax.swing.JScrollPane getMsgScrollPane() {
    return msgScrollPane;
}

public void setMsgScrollPane(javax.swing.JScrollPane msgScrollPane) {
    this.msgScrollPane = msgScrollPane;
}

public javax.swing.JTextArea getMsgTextArea() {
    return msgTextArea;
}

public void setMsgTextArea(javax.swing.JTextArea msgTextArea) {
    this.msgTextArea = msgTextArea;
}

public String getMsgText() {
    return this.msgTextArea.getText();
}

public void setMsgText(String msgText) {
    this.msgTextArea.setText(msgText);
    msgTextArea.setCaretPosition(0);
    msgScrollPane.getVerticalScrollBar().setValue(0);
}

public javax.swing.JButton getNoButton() {
    return noButton;
}

public void setNoButton(javax.swing.JButton noButton) {
    this.noButton = noButton;
}

public javax.swing.JButton getYesButton() {
    return yesButton;
}

public void setYesButton(javax.swing.JButton yesButton) {
    this.yesButton = yesButton;
}

public javax.swing.JPanel getYesNoPanel() {
    return yesNoPanel;
}

public void setYesNoPanel(javax.swing.JPanel yesNoPanel) {
    this.yesNoPanel = yesNoPanel;
}


public static void main(String args[]) {
    /* Create and display the dialog */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            Logger logger = null;
            int dialogType = 1;
            String title = "Mock Dialog";
            mock2Dialog dialog = new mock2Dialog(
                    new javax.swing.JFrame(), false, title, dialogType,
                    logger);
            dialog.addWindowListener(new java.awt.event.WindowAdapter() {
                @Override
                public void windowClosing(java.awt.event.WindowEvent e) {
                    System.exit(0);
                }
            }); //nested a method in another methods arguments                          

            dialog.setVisible(true);
            dialog.msgTextArea
                    .setText(" Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam sit amet fringilla nunc.\n "
                            + "Duis sem nulla, egestas vel elit vitae, pulvinar semper nunc. Nam in nisi quis turpis pellentesque pulvinar. \n"
                            + "Nulla facilisi. Pellentesque ac rhoncus ante. Mauris ut magna nibh. Ut eget dapibus diam, sed iaculis erat. "
                            + "Vestibulum faucibus neque nisl, non imperdiet libero elementum sed. Fusce molestie eros id ligula consectetur ultrices.");
        }
    });

}
}

Don't use GroupLayout. GroupLayout is generally only used by development tools that generate code because the layout is hard to use when written by hand. Use a combination of other layout managers on nested panels to achieve your desired result. — camickr, Dec 13 '13 at 01:28
After all the research and seeing peoples answers on other questions I definitely agree with you camickr. However, this is a small part of a much larger app that's been generated with development tools and I thought for continuity sake it would be better to work within that GroupLayout framework. It's sounding as though there may not be a solution (good or otherwise) to the problem using GroupLayout though... Thank you for the response! — Godaigo, Dec 17 '13 at 23:24

score 1 · Accepted Answer · answered Dec 13 '13 at 03:22

I find GroupLayout to be fine to code by hand, certainly no harder than GridBagLayout, though I can certainly see why it would be a favorite for tools to use. But it is meant for putting things into columns and rows, not for centering buttons. You have the wrong layout manager.

To put a panel in the center of a screen that you want the user to be able to resize (which should be the default), you can put your panel in the BorderLayout.CENTER of a BorderLayout (which is the default layout manager on a JFrame). Now, by default, the panel will also stretch to fit the frame unless you also put some things in the NORTH, SOUTH, EAST, and/or WEST portions of the BorderLayout. Whether this works for you depends on what you're doing.

I also understand you can put the panel to be centered into a GridBagLayout with nothing else in it, and that will center it. It isn't my method, but I mention it for completeness.

If you want a group of buttons to stay centered, first choose a layout manager for a panel to hold the buttons -- grid layout works only if you want the buttons to be the same size, you can use GropuLayout to put them in rows and columns, a BoxLayout can put a string of buttons horizontally or stack them vertically.

Then you can put THAT panel into another panel with a different layout - say, in the SOUTH portion of a BorderLayout - to center them horizontally, or the WEST portion of a BorderLayout to center them vertically. This is what rcamrick is talking about when he mentions "nested panels".

rcook, I'm going to give this a shot and see if I can get this working with the BorderLayout. I'm going to try this with just setting the JPanel that holds the buttons to BorderLayout and set the buttons to CENTER and see if that works. Thanks for the help! — Godaigo, Dec 19 '13 at 00:21
Be sure to upvote comments and answers that you find helpful, and mark as "accepted" any (first or best) answers to question you post on stack overflow. That's part of how the system works... — arcy, Dec 19 '13 at 03:09
Just to update, I did finally get this working by getting rid of the JLayeredPane and using a base JPanel which holds the other JPanels. I used nested GridBagLayouts for the JPanels within the existing GroupLayout containers and it seems to work. Thanks for the help! — Godaigo, Dec 27 '13 at 18:38

What's the best way to keep JButtons centered in a JPanel using GroupLayout on JPanel resize

1 Answers1