Java Tutorial/Swing/JWindow

Center window

/*
 * Copyright (c) 1998-2002 Carnegie Mellon University.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS"" AND
 * ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY
 * NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

import java.awt.*;
public abstract class Win {
    public static void center (Window window, Component ref) {
        position (window, ref, 0.5, 0.5);
    }
    public static void position (Window frame, Component ref, 
                                 double xfrac, double yfrac) {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        Dimension size = frame.getSize();
        Dimension refSize = (ref != null) 
            ? ref.getSize() 
            : screenSize;
        Point origin = (ref != null)
            ? ref.getLocationOnScreen () 
            : new Point (0, 0);
        int x = origin.x + relativePoint (xfrac, refSize.width, size.width);
        int y = origin.y + relativePoint (yfrac, refSize.height, size.height);
        // make sure frame is entirely on screen
        x = Math.max (0, Math.min (screenSize.width - size.width, x));
        y = Math.max (0, Math.min (screenSize.height - size.height, y));
        
        frame.setLocation (x, y);
    }
    static int relativePoint (double frac, int parentLength, int childLength) {
        if (frac < 0)
            return (int) (frac * childLength);
        else if (frac > 1)
            return (int) (parentLength + (frac - 2) * childLength);
        else
            return (int) (frac * (parentLength - childLength));
    }

    public static Frame findFrame (Component comp) {
        for (; comp!=null; comp = comp.getParent ())
            if (comp instanceof Frame) {
                return (Frame)comp;
            }
        return null;
    }
    public static Frame findFrameOrMakeFrame (Component parent) {
        return (parent != null) ? findFrame (parent) : new Frame ();
    }
        
}

Center Within Parent

/*
 * Copyright (C) 2001-2004 Colin Bell
 * colbell@users.sourceforge.net
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

import java.awt.ruponent;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.Frame;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.Insets;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.Window;
import java.awt.geom.Rectangle2D;
import java.beans.PropertyVetoException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.SwingUtilities;
/**
 * Common GUI utilities accessed via static methods.
 * 
 * @author 
 */
public class GUIUtils {
  private static JFrame _mainFrame;
  /**
   * Centers <CODE>wind</CODE> within its parent. If it has no parent then
   * center within the screen. If centering would cause the title bar to go
   * above the parent (I.E. cannot see the titlebar and so cannot move the
   * window) then move the window down.
   * 
   * @param wind
   *          The Window to be centered.
   * 
   * @throws IllegalArgumentException
   *           If <TT>wind</TT> is <TT>null</TT>.
   */
  public static void centerWithinParent(Window wind) {
    if (wind == null) {
      throw new IllegalArgumentException("null Window passed");
    }
    final Container parent = wind.getParent();
    if (parent != null && parent.isVisible()) {
      center(wind, new Rectangle(parent.getLocationOnScreen(), parent.getSize()));
    } else {
      centerWithinScreen(wind);
    }
  }
  /**
   * Centers passed internal frame within its desktop area. If centering would
   * cause the title bar to go off the top of the screen then move the window
   * down.
   * 
   * @param frame
   *          The internal frame to be centered.
   * 
   * @throws IllegalArgumentException
   *           If <TT>frame</TT> is <TT>null</TT>.
   */
  public static void centerWithinDesktop(JInternalFrame frame) {
    if (frame == null) {
      throw new IllegalArgumentException("null JInternalFrame passed");
    }
    final Container parent = frame.getDesktopPane();
    if (parent != null && parent.isVisible()) {
      center(frame, new Rectangle(new Point(0, 0), parent.getSize()));
    }
  }
  /**
   * Centers <CODE>wind</CODE> within the screen. If centering would cause the
   * title bar to go off the top of the screen then move the window down.
   * 
   * @param wind
   *          The Window to be centered.
   * 
   * @throws IllegalArgumentException
   *           If <TT>wind</TT> is <TT>null</TT>.
   */
  public static void centerWithinScreen(Window wind) {
    if (wind == null) {
      throw new IllegalArgumentException("null Window passed");
    }
    final Toolkit toolKit = Toolkit.getDefaultToolkit();
    final Rectangle rcScreen = new Rectangle(toolKit.getScreenSize());
    final Dimension windSize = wind.getSize();
    final Dimension parentSize = new Dimension(rcScreen.width, rcScreen.height);
    if (windSize.height > parentSize.height) {
      windSize.height = parentSize.height;
    }
    if (windSize.width > parentSize.width) {
      windSize.width = parentSize.width;
    }
    center(wind, rcScreen);
  }
  /**
   * Centers <CODE>wind</CODE> within the passed rectangle.
   * 
   * @param wind
   *          The Window to be centered.
   * @param rect
   *          The rectangle (in screen coords) to center <CODE>wind</CODE>
   *          within.
   * 
   * @throws IllegalArgumentException
   *           If <TT>Window</TT> or <TT>Rectangle</TT> is <TT>null</TT>.
   */
  private static void center(Component wind, Rectangle rect) {
    if (wind == null || rect == null) {
      throw new IllegalArgumentException("null Window or Rectangle passed");
    }
    Dimension windSize = wind.getSize();
    int x = ((rect.width - windSize.width) / 2) + rect.x;
    int y = ((rect.height - windSize.height) / 2) + rect.y;
    if (y < rect.y) {
      y = rect.y;
    }
    wind.setLocation(x, y);
  }
}

Difference between JFrame and JWindow

import javax.swing.JFrame;
import javax.swing.JWindow;
public class Main {
  public static void main(String[] args) {
    JFrame f = new JFrame("The Frame");
    f.setSize(300, 300);
    f.setLocation(100, 100);
    JWindow w = new JWindow();
    w.setSize(300, 300);
    w.setLocation(500, 100);
    f.setVisible(true);
    w.setVisible(true);
  }
}

Extending JWindow

If you need to extend JWindow, the class has two protected methods of importance:

protected void windowInit()
protected JRootPane createRootPane()

Have borders on a JWindow/JFrame

import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JWindow;
public class Main{
  public static void main(String s[]) {
    JWindow win = new JWindow();
    JPanel pan = new JPanel();
    win.add(pan, "Center");
    pan.setLayout(new FlowLayout());
    pan.add(new JButton("Hello"));
    win.setSize(200, 200);
    win.setVisible(true);
  }
}