Graphical User Interfaces - Java - page 591

Discussion

The code for this is pretty simple. The part that might take a while to figure out is the Dimen-
sion of the screen. Two methods can help: getScreenSize() in the Toolkit class and the
static method getDefaultToolkit() . The Toolkit class relates to the underlying window-
ing toolkit; it has several subclasses, including two different ones for X Windows on Unix
(Motif and non-Motif), another for Macintosh, and so on. Put these together and you have
the Dimension you need.

Centering a Window is such a common need that I have packaged it in its own little class:
UtilGUI . Here is the complete source for UtilGUI , which I'll use without comment from
now on:

// package com.darwinsys.swingui;
public

public class class UtilGUI UtilGUI {

/** Centre a Window, Frame, JFrame, Dialog, etc. */
public

public static final Window w ) {

// After packing a Frame or Dialog, centre it on the screen.
Dimension us = w . getSize (),
them = Toolkit . getDefaultToolkit (). getScreenSize ();

static void void centre ( final

int int newX = ( them . width - us . width ) / 2 ;

int int newY = ( them . height - us . height )/ 2 ;

w . setLocation ( newX , newY );

}

/** Center a Window, Frame, JFrame, Dialog, etc.,
* but do it the American Spelling Way :-)
*/
public public static static void void center ( final final Window w ) {

UtilGUI . centre ( w );

}

/** Maximize a window, the hard way. */
public public static static void void maximize ( final final Window w ) {

Dimension them =
Toolkit . getDefaultToolkit (). getScreenSize ();
w . setBounds ( 0 , 0 , them . width , them . height );

}

/**
* Copy a string value to the system copy buffer
*/