GUI Components and Techniques

How can you display buttons and execute methods within the buttons?

To create a button just do this:

Button b = new Button("Some Label")
add(b);

i.e (within a Container)

Panel p = new Panel()
p.setLayout(new FlowLayout());
p.add(new Button("one"));
p.add(new Button("two"));
p.add(new Button("three"));
add(p);

To handle button events there are two main ways _without_ sub-classing the button:

// The following code handles the button event using the label,
// can however compare objects(i.e if(evt.target instanceof Button)
// instead of comparing labels as we are doing below
public boolean handleEvent(Event evt)
{
    switch(evt.id)
    {
        case Event.ACTION_EVENT:
        {
            // Note: Java here is converting "Some Label" to
            // to a String and comparing it to evt.arg which
            // is the label of the button just pressed.
            if("Some Label".equals(evt.arg))
            {
                  System.out.println("This button has been hit");
                  // Call a method of yours call myMethod()
                  myMethod();
                  return true;
            }
        }
    default:
        return false;

}
// Or

public boolean action(Event evt, Object arg)
{
    if("Some Label".equals(arg))
    {
        System.out.prinln("This button has been hit");
        myMethod();
        return true;
    }
    return false;
}

How do I get and use the list of installed fonts using getFontList()?

To get a String array of the fonts supported on your current platform:

String[] fonts= Toolkit.getDefaultToolkit().getFontList();

Note that there appears to be a bug that surfaces if one tries to instantiate too many Font objects.

The basic way to "open" a font is:

Font newFont = new Font(fontName, Font.BOLD, fontSize);

where fontName is one of the strings returned by getFontList(). To use this font,

g.setFont(iconFont);

How do I change the color of a Label?

/*  
    java applet code written by
    M.K. Kwong, MCS, Argonne National Laboratory
    kwong@mcs.anl.gov
    Date: Jan 1996 
   
    Permission to use, copy, modify, and distribute this 
    software and its documentation for NON-COMMERCIAL or 
    COMMERCIAL purposes and without fee is hereby granted.
*/

import java.lang.*;
import java.applet.Applet;
import java.awt.*;

public class RedLab extends java.applet.Applet {

    public void init() {
        setBackground(Color.white);

     Panel p = new Panel();
     p.setLayout(new FlowLayout());
     Label lab = new Label("red",Label.CENTER);
     lab.setBackground(Color.red);
     p.add(lab);
     add(p);
    }
}

Note from the editor: This seems to not work on Windows95 at this time (JDK1.0, Netscape 2.0). It does, however, work on Solaris.

How do I change the page increment in a scrolbar?

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