How do I center a JDialog on screen?

How do I go about positioning a JDialog at the center of the screen?

Asked by: Max213 | Posted: 23-01-2022

Answer 1

In Java 1.4+ you can do:

final JDialog d = new JDialog();
d.setSize(200,200);
d.setLocationRelativeTo(null);
d.setVisible(true);

Or perhaps (pre 1.4):

final JDialog d = new JDialog();
d.setSize(200, 200);
final Toolkit toolkit = Toolkit.getDefaultToolkit();
final Dimension screenSize = toolkit.getScreenSize();
final int x = (screenSize.width - d.getWidth()) / 2;
final int y = (screenSize.height - d.getHeight()) / 2;
d.setLocation(x, y);
d.setVisible(true);

Answered by: Edgar642 | Posted: 24-02-2022

Answer 2

Use this line after the pack() method:

setLocation((Toolkit.getDefaultToolkit().getScreenSize().width)/2 - getWidth()/2, (Toolkit.getDefaultToolkit().getScreenSize().height)/2 - getHeight()/2);

Answered by: Daryl361 | Posted: 24-02-2022

Answer 3

Two helpers for centering within the screen or within the parent.

// Center on screen ( absolute true/false (exact center or 25% upper left) )
public void centerOnScreen(final Component c, final boolean absolute) {
    final int width = c.getWidth();
    final int height = c.getHeight();
    final Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    int x = (screenSize.width / 2) - (width / 2);
    int y = (screenSize.height / 2) - (height / 2);
    if (!absolute) {
        x /= 2;
        y /= 2;
    }
    c.setLocation(x, y);
}

// Center on parent ( absolute true/false (exact center or 25% upper left) )
public void centerOnParent(final Window child, final boolean absolute) {
    child.pack();
    boolean useChildsOwner = child.getOwner() != null ? ((child.getOwner() instanceof JFrame) || (child.getOwner() instanceof JDialog)) : false;
    final Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    final Dimension parentSize = useChildsOwner ? child.getOwner().getSize() : screenSize ;
    final Point parentLocationOnScreen = useChildsOwner ? child.getOwner().getLocationOnScreen() : new Point(0,0) ;
    final Dimension childSize = child.getSize();
    childSize.width = Math.min(childSize.width, screenSize.width);
    childSize.height = Math.min(childSize.height, screenSize.height);
    child.setSize(childSize);        
    int x;
    int y;
    if ((child.getOwner() != null) && child.getOwner().isShowing()) {
        x = (parentSize.width - childSize.width) / 2;
        y = (parentSize.height - childSize.height) / 2;
        x += parentLocationOnScreen.x;
        y += parentLocationOnScreen.y;
    } else {
        x = (screenSize.width - childSize.width) / 2;
        y = (screenSize.height - childSize.height) / 2;
    }
    if (!absolute) {
        x /= 2;
        y /= 2;
    }
    child.setLocation(x, y);
}

Answered by: Sawyer522 | Posted: 24-02-2022

Answer 4

here's my solution to retrieve screen dimension with multiple monitors.

import java.awt.*;
import javax.swing.JFrame;

/**
 * MÃ©thodes statiques pour rÃ©cupÃ©rer les informations d'un Ã©cran.
 *
 * @author Jean-Claude Stritt
 * @version 1.0 / 24.2.2009
 */
public class ScreenInfo {

  /**
   * Permet de rÃ©cupÃ©rer le numÃ©ro de l'Ã©cran par rapport Ã  la fenÃªtre affichÃ©e.
   * @return le numÃ©ro 1, 2, ... (ID) de l'Ã©cran
   */
  public static int getScreenID( JFrame jf ) {
    int scrID = 1;
    GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] gd = ge.getScreenDevices();
    for (int i = 0; i < gd.length; i++) {
      GraphicsConfiguration gc = gd[i].getDefaultConfiguration();
      Rectangle r = gc.getBounds();
      if (r.contains(jf.getLocation())) {
        scrID = i+1;
      }
    }
    return scrID;
  }

  /**
   * Permet de rÃ©cupÃ©rer la dimension (largeur, hauteur) en px d'un Ã©cran spÃ©cifiÃ©.
   * @param scrID --> le nÂ° d'Ã©cran
   * @return la dimension (largeur, hauteur) en pixels de l'Ã©cran spÃ©cifiÃ©
   */
  public static Dimension getScreenDimension( int scrID ) {
    Dimension d = new Dimension(0, 0);
    if (scrID > 0) {
      GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
      DisplayMode mode = ge.getScreenDevices()[scrID - 1].getDisplayMode();
      d.setSize(mode.getWidth(), mode.getHeight());
    }
    return d;
  }

  /**
   * Permet de rÃ©cupÃ©rer la largeur en pixels d'un Ã©cran spÃ©cifiÃ©.
   * @param scrID --> le nÂ° d'Ã©cran
   * @return la largeur en px de l'Ã©cran spÃ©cifiÃ©
   */
  public static int getScreenWidth( int scrID ) {
    Dimension d = getScreenDimension(scrID);
    return d.width;
  }

  /**
   * Permet de rÃ©cupÃ©rer la hauteur en pixels d'un Ã©cran spÃ©cifiÃ©.
   * @param scrID --> le nÂ° d'Ã©cran
   * @return la hauteur en px de l'Ã©cran spÃ©cifiÃ©
   */
  public static int getScreenHeight( int scrID ) {
    Dimension d = getScreenDimension(scrID);
    return d.height;
  }

}

Answered by: Wilson218 | Posted: 24-02-2022

Answer 5

AFAIK you can pass a GraphicEnvironment to each JDialog/JFrame/JWindow constructor. This object describes the monitor to use.

Answered by: Arthur593 | Posted: 24-02-2022

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