Hello experts!
As this program is now it's works perfectly when running as a application or
as an Applet.
Now to my question if I just change this row "public class Converter extends
Applet " in class Converter below
that it extends from a Frame instead from an Applet
then the whole program krasch with message "An exception
'java.lang.Ille galArgumentExce ption' has occured in ...
I mean that if I run this program as an application I should be able to set
that it extends from Frame. I don't want to have extends Applet because I
will not run it as an applet.
So what must be changed before being able to run the program with extends
Frame?
If I comment this row out "f.add("Center" , converter); " from method main in
the Converter class
the application starts but without an empty window.
The program is rather big but I don't think you have to look at the whole
program for solve my problem.
public class Converter extends Applet
{
import java.awt.*;
import java.awt.event. *;
import java.util.*;
import java.applet.App let;
public class Converter extends Applet
{
ConversionPanel metricPanel, usaPanel;
Unit[] metricDistances = new Unit[3];
Unit[] usaDistances = new Unit[4];
/**
* Create the ConversionPanel s (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("Centimete rs", 0.01);
metricDistances[1] = new Unit("Meters", 1.0);
metricDistances[2] = new Unit("Kilometer s", 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 ConversionPanel s to the Converter.
add(metricPanel );
add(usaPanel);
}
/**
* Does the conversion from metric to U.S., or vice versa, and
* updates the appropriate ConversionPanel .
*/
void convert(Convers ionPanel from)
{
ConversionPanel to;
if (from == metricPanel)
to = usaPanel;
else
to = metricPanel;
double multiplier = from.getMultipl ier() / to.getMultiplie r();
to.setValue(mul tiplier * from.getValue() );
}
/** Draws a box around this panel. */
public void paint(Graphics g)
{
Dimension d = getSize();
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 getInsets()
{
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.
Frame f = new Frame("Converte r Applet/Application");
f.addWindowList ener(new WindowAdapter()
{
public void windowClosing(W indowEvent e)
{
System.exit(0);
}
});
//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.setVisible(tr ue);
}
}
class ConversionPanel extends Panel
implements ActionListener,
AdjustmentListe ner,
ItemListener
{
TextField textField;
Choice unitChooser;
Scrollbar slider;
int max = 10000;
int block = 100;
Converter controller;
Unit[] units;
ConversionPanel (Converter myController, String myTitle, Unit[] myUnits)
{
//Initialize this ConversionPanel to use a GridBagLayout.
GridBagConstrai nts c = new GridBagConstrai nts();
GridBagLayout gridbag = new GridBagLayout() ;
setLayout(gridb ag);
//Save arguments in instance variables.
controller = myController;
units = myUnits;
//Set up default layout constraints.
c.fill = GridBagConstrai nts.HORIZONTAL;
//Add the label. It displays this panel's title, centered.
Label label = new Label(myTitle, Label.CENTER);
c.gridwidth = GridBagConstrai nts.REMAINDER; //It ends a row.
gridbag.setCons traints(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; //Use maximum horizontal space...
c.gridwidth = 1; //The default value.
gridbag.setCons traints(textFie ld, c);
add(textField);
textField.addAc tionListener(th is);
//Add the pop-up list (Choice).
unitChooser = new Choice();
for (int i = 0; i < units.length; i++)
{ //Populate it.
unitChooser.add (units[i].description);
}
c.weightx = 0.0; //The default value.
c.gridwidth = GridBagConstrai nts.REMAINDER; //End a row.
gridbag.setCons traints(unitCho oser, c);
add(unitChooser );
unitChooser.add ItemListener(th is);
//Add the slider. It's horizontal, and it has the maximum
//value specified by the instance variable max. Its initial
//and minimum values are the default (0). A click increments
//the value by block units.
slider = new Scrollbar(Scrol lbar.HORIZONTAL );
slider.setMaxim um(max + 10);
slider.setBlock Increment(block );
c.gridwidth = 1; //The default value.
gridbag.setCons traints(slider, c);
add(slider);
slider.addAdjus tmentListener(t his);
}
/**
* Returns the multiplier (units/meter) for the currently
* selected unit of measurement.
*/
double getMultiplier()
{
int i = unitChooser.get SelectedIndex() ;
return units[i].multiplier;
}
/** Draws a box around this panel. */
public void paint(Graphics g)
{
Dimension d = getSize();
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 getInsets()
{
return new Insets(5,5,5,8) ;
}
/**
* Gets the current value in the text field.
* It's guaranteed to be the same as the value
* in the scroller (subject to rounding, of course).
*/
double getValue()
{
double f;
try
{
f = (double)Double. valueOf(textFie ld.getText()).d oubleValue();
}
catch (java.lang.Numb erFormatExcepti on e)
{
f = 0.0;
}
return f;
}
public void actionPerformed (ActionEvent e)
{
setSliderValue( getValue());
controller.conv ert(this);
}
public void itemStateChange d(ItemEvent e)
{
controller.conv ert(this);
}
/** Respond to the slider. */
public void adjustmentValue Changed(Adjustm entEvent e)
{
textField.setTe xt(String.value Of(e.getValue() ));
controller.conv ert(this);
}
/** Set the values in the slider and text field. */
void setValue(double f)
{
setSliderValue( f);
textField.setTe xt(String.value Of((float)f));
}
/** Set the slider value. */
void setSliderValue( double f)
{
int sliderValue = (int)f;
if (sliderValue > max)
sliderValue = max;
if (sliderValue < 0)
sliderValue = 0;
slider.setValue (sliderValue);
}
}
class Unit
{
String description;
double multiplier;
Unit(String description, double multiplier)
{
super();
this.descriptio n = description;
this.multiplier = multiplier;
}
public String toString()
{
String s = "Meters/" + description + " = " + multiplier;
return s;
}
}
