/*
* Copyright (c) 1995, 1996 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software
* and its documentation for NON-COMMERCIAL purposes and without
* fee is hereby granted provided that this copyright notice
* appears in all copies. Please refer to the file "copyright.html"
* for further important copyright and licensing information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*/
import java.awt.*;
import java.util.*;
import java.applet.Applet;
public class Converter extends Applet {
ConversionPanel metricPanel, usaPanel;
Unit[] metricDistances = new Unit[3];
Unit[] usaDistances = new Unit[4];
/**
* Create the ConversionPanels (one for metric, another for U.S.).
* I used "U.S." because although Imperial and U.S. distance
* measurements are the same, this program could be extended to
* include volume measurements, which aren't the same.
*/
public void init() {
//Use a GridLayout with 2 rows, as many columns as necessary,
//and 5 pixels of padding around all edges of each cell.
setLayout(new GridLayout(2,0,5,5));
//Create Unit objects for metric distances, and then
//instantiate a ConversionPanel with these Units.
metricDistances[0] = new Unit("Centimeters", 0.01);
metricDistances[1] = new Unit("Meters", 1.0);
metricDistances[2] = new Unit("Kilometers", 1000.0);
metricPanel = new ConversionPanel(this, "Metric System",
metricDistances);
//Create Unit objects for U.S. distances, and then
//instantiate a ConversionPanel with these Units.
usaDistances[0] = new Unit("Inches", 0.0254);
usaDistances[1] = new Unit("Feet", 0.305);
usaDistances[2] = new Unit("Yards", 0.914);
usaDistances[3] = new Unit("Miles", 1613.0);
usaPanel = new ConversionPanel(this, "U.S. System", usaDistances);
//Add both ConversionPanels to the Converter.
add(metricPanel);
add(usaPanel);
//Calling the validate method here can help applets.
//It's unnecessary when this program runs as an application.
validate();
}
/**
* Does the conversion from metric to U.S., or vice versa, and
* updates the appropriate ConversionPanel.
*/
void convert(ConversionPanel from) {
ConversionPanel to;
if (from == metricPanel)
to = usaPanel;
else
to = metricPanel;
double multiplier = from.getMultiplier() / to.getMultiplier();
to.setValue(from.getValue() * multiplier);
}
/** Draws a box around this panel. */
public void paint(Graphics g) {
Dimension d = size();
g.drawRect(0,0, d.width - 1, d.height - 1);
}
/**
* Puts a little breathing space between
* the panel and its contents, which lets us draw a box
* in the paint() method.
*/
public Insets insets() {
return new Insets(5,5,5,5);
}
/** Executed only when this program runs as an application. */
public static void main(String[] args) {
//Create a new window.
MainFrame f = new MainFrame("Converter Applet/Application");
//Create a Converter instance.
Converter converter = new Converter();
//Initialize the Converter instance.
converter.init();
//Add the Converter to the window and display the window.
f.add("Center", converter);
f.pack(); //Resizes the window to its natural size.
f.show();
}
}
class ConversionPanel extends Panel {
TextField textField;
Scrollbar slider;
Choice unitChooser;
int min = 0;
int max = 10000;
Converter controller;
Unit[] units;
ConversionPanel(Converter myController, String myTitle, Unit[] myUnits) {
//Initialize this ConversionPanel to use a GridBagLayout.
GridBagConstraints c = new GridBagConstraints();
GridBagLayout gridbag = new GridBagLayout();
setLayout(gridbag);
//Save arguments in instance variables.
controller = myController;
units = myUnits;
//Set up default layout constraints.
c.fill = GridBagConstraints.HORIZONTAL;
//Add the label. It displays this panel's title, centered.
Label label = new Label(myTitle, Label.CENTER);
c.gridwidth = GridBagConstraints.REMAINDER; //It ends a row.
gridbag.setConstraints(label, c);
add(label);
//Add the text field. It initially displays "0" and needs
//to be at least 10 columns wide.
textField = new TextField("0", 10);
c.weightx = 1.0; //This component should use all available horizontal space...
c.gridwidth = 1; //The default value.
gridbag.setConstraints(textField, c);
add(textField);
//Add the pop-up list (Choice).
unitChooser = new Choice();
for (int i = 0; i < units.length; i++) { //Populate it.
unitChooser.addItem(units[i].description);
}
c.weightx = 0.0; //The default value.
c.gridwidth = GridBagConstraints.REMAINDER; //End a row.
gridbag.setConstraints(unitChooser, c);
add(unitChooser);
//Add the slider. It's horizontal, its initial value is 0,
//a click increments the value by 100 pixels, and it has the
//minimum and maximum values specified by the instance variables
//min and max.
slider = new Scrollbar(Scrollbar.HORIZONTAL, 0, 100, min, max);
c.gridwidth = 1; //The default value.
gridbag.setConstraints(slider, c);
add(slider);
}
/**
* Returns the multiplier (units/meter) for the currently
* selected unit of measurement.
*/
double getMultiplier() {
int i = unitChooser.getSelectedIndex();
return (units[i].multiplier);
}
/** Draws a box around this panel. */
public void paint(Graphics g) {
Dimension d = size();
g.drawRect(0,0, d.width - 1, d.height - 1);
}
/**
* Puts a little breathing space between
* the panel and its contents, which lets us draw a box
* in the paint() method.
* We add more pixels to the right, to work around a
* Choice bug.
*/
public Insets insets() {
return new Insets(5,5,5,8);
}
/**
* Gets the current value in the text field.
* That's guaranteed to be the same as the value
* in the scroller (subject to rounding, of course).
*/
double getValue() {
double f;
try {
f = Double.valueOf(textField.getText()).doubleValue();
} catch (java.lang.NumberFormatException e) {
f = 0.0;
}
return f;
}
/** Respond to user actions on controls. */
public boolean action(Event e, Object arg) {
if (e.target instanceof TextField) {
setSliderValue(getValue());
controller.convert(this);
return true;
}
if (e.target instanceof Choice) {
controller.convert(this);
return true;
}
return false;
}
/** Respond to the slider. */
public boolean handleEvent(Event e) {
if (e.target instanceof Scrollbar) {
textField.setText(String.valueOf(slider.getValue()));
controller.convert(this);
}
return super.handleEvent(e);
}
/** Set the values in the slider and text field. */
void setValue(double f) {
setSliderValue(f);
textField.setText(String.valueOf(f));
}
/** Set the slider value. */
void setSliderValue(double f) {
int sliderValue = (int)f;
if (sliderValue > max)
sliderValue = max;
if (sliderValue < min)
sliderValue = min;
slider.setValue(sliderValue);
}
}
class Unit {
String description;
double multiplier;
Unit(String description, double multiplier) {
super();
this.description = description;
this.multiplier = multiplier;
}
public String toString() {
String s = "Meters/" + description + " = " + multiplier;
return s;
}
}
/** Provides a window if this program is run as an application. */
class MainFrame extends Frame {
MainFrame(String title) {
super(title);
}
public boolean handleEvent(Event e) {
if (e.id == Event.WINDOW_DESTROY) {
System.exit(0);
}
return super.handleEvent(e);
}
}