Java 1996 August/Java - Summer 1996.iso/rockridge/ui/anatomy/example/Converter.java

Java Source | 1995-11-13 | 5.3 KB | 206 lines

/* This program could use some layout work, and the functionality
 * could use some tweaking, but it seems to basically work.
 */
import java.awt.*;
import java.util.*;
import java.applet.Applet;

public class Converter extends Applet {
    Frame window;
    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() {
    setLayout(new GridLayout(2,0,10,10));

    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);

    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(metricPanel);
    add(usaPanel);
    }

    /** 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(3,3,3,3);
    }

    public static void main(String args[]) {
    Frame f = new Frame("Converter Applet/Application");
    Converter converter = new Converter();

    converter.init();

    f.add("Center", converter);
    f.pack();
    f.resize(250, 165);
    f.show();
    }

}


class ConversionPanel extends Panel {
    String title;
    TextField textField;
    Scrollbar slider;
    Choice unitChooser;
    int min = 0;
    int max = 10000;
    Converter controller;
    Unit units[];

    //TO DO: Should make both panels' choices the same width.
    ConversionPanel(Converter myController, String myTitle, Unit myUnits[]) {
    super();
    controller = myController;
    title = myTitle;
    units = myUnits;

    //Build the left half of this panel.
    textField = new TextField("0", 10);
    slider = new Scrollbar(Scrollbar.HORIZONTAL, 0, 100, min, max);
    Panel leftHalf = new Panel();
    leftHalf.setLayout(new BorderLayout());
    leftHalf.add("Center", textField);
    leftHalf.add("South", slider);

    //Build the right half of this panel.
    unitChooser = new Choice();
    for (int i = 0; i < units.length; i++) {
        unitChooser.addItem(units[i].description);
    }

    //Put everything in this panel.
    setLayout(new BorderLayout());
    add("North", new Label(title, Label.CENTER));
    add("Center", leftHalf);
    add("East", unitChooser);
    }

    /** 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.
      */
    public Insets insets() {
    // Right offset is more than left, due to Choice bug.
    return new Insets(2,10,2,15);
    }

    /** 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. */
    public boolean handleEvent(Event e) {
    if (e.target instanceof Scrollbar) {
        textField.setText(String.valueOf(slider.getValue()));
        controller.convert(this);
        return true;
    } else if (e.target instanceof TextField) {
        setSliderValue(getValue());
        controller.convert(this);
        return true;
    } else if (e.target instanceof Choice) {
        controller.convert(this);
        return true;
    }
    return false;
    }

    /** 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;
    }
}