There are many kinds of computers out there. It’s unlikely that
you’d find yourself running on a desktop computer with no
serial ports, but you might find that there is only one and
it’s already in use by another program. Or you might want a
parallel port and find that the computer has only serial ports. This
program shows you how to use the static
CommPortIdentifier method
getPortIdentifiers( ). This gives you an
Enumeration (Section 7.5) of the
serial and parallel ports available on your system. My routine
populate( ) processes this list and loads it into
a pair of JComboBoxes (graphical choosers; see
Section 13.2), one for serial ports and one for
parallel (there is also a third, unknown, to cover future expansion
of the API). The routine makeGUI creates the
JComboBoxes and arranges to notify us when the
user picks one from either of the lists. The name of the selected
port is displayed at the bottom of the window. So that you
won’t have to know much about it to use it, there are public
methods getSelectedName( ), which returns the name
of the last port chosen by either JComboBox and
getSelectedIdentifier( ), which returns an object
called a CommPortIdentifier corresponding to the
selected port name. Figure 11-1 shows the port chooser in action.
Example 11-1 shows the code.
Example 11-1. PortChooser.java
import java.io.*;
import javax.comm.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import com.darwinsys.utilWindowCloser;
/**
* Choose a port, any port!
*
* Java Communications is a "standard extension" and must be downloaded
* and installed separately from the JDK before you can even compile this
* program.
*
*/
public class PortChooser extends JDialog implements ItemListener {
/** A mapping from names to CommPortIdentifiers. */
protected HashMap map = new HashMap( );
/** The name of the choice the user made. */
protected String selectedPortName;
/** The CommPortIdentifier the user chose. */
protected CommPortIdentifier selectedPortIdentifier;
/** The JComboBox for serial ports */
protected JComboBox serialPortsChoice;
/** The JComboBox for parallel ports */
protected JComboBox parallelPortsChoice;
/** The JComboBox for anything else */
protected JComboBox other;
/** The SerialPort object */
protected SerialPort ttya;
/** To display the chosen */
protected JLabel choice;
/** Padding in the GUI */
protected final int PAD = 5;
/** This will be called from either of the JComboBoxes when the
* user selects any given item.
*/
public void itemStateChanged(ItemEvent e) {
// Get the name
selectedPortName = (String)((JComboBox)e.getSource()).getSelectedItem( );
// Get the given CommPortIdentifier
selectedPortIdentifier = (CommPortIdentifier)map.get(selectedPortName);
// Display the name.
choice.setText(selectedPortName);
}
/* The public "getter" to retrieve the chosen port by name. */
public String getSelectedName( ) {
return selectedPortName;
}
/* The public "getter" to retrieve the selection by CommPortIdentifier. */
public CommPortIdentifier getSelectedIdentifier( ) {
return selectedPortIdentifier;
}
/** A test program to show up this chooser. */
public static void main(String[] ap) {
PortChooser c = new PortChooser(null);
c.setVisible(true); // blocking wait
System.out.println("You chose " + c.getSelectedName( ) +
" (known by " + c.getSelectedIdentifier( ) + ").");
System.exit(0);
}
/** Construct a PortChooser --make the GUI and populate the ComboBoxes.
*/
public PortChooser(JFrame parent) {
super(parent, "Port Chooser", true);
makeGUI( );
populate( );
finishGUI( );
}
/** Build the GUI. You can ignore this for now if you have not
* yet worked through the GUI chapter. Your mileage may vary.
*/
protected void makeGUI( ) {
Container cp = getContentPane( );
JPanel centerPanel = new JPanel( );
cp.add(BorderLayout.CENTER, centerPanel);
centerPanel.setLayout(new GridLayout(0,2, PAD, PAD));
centerPanel.add(new JLabel("Serial Ports", JLabel.RIGHT));
serialPortsChoice = new JComboBox( );
centerPanel.add(serialPortsChoice);
serialPortsChoice.setEnabled(false);
centerPanel.add(new JLabel("Parallel Ports", JLabel.RIGHT));
parallelPortsChoice = new JComboBox( );
centerPanel.add(parallelPortsChoice);
parallelPortsChoice.setEnabled(false);
centerPanel.add(new JLabel("Unknown Ports", JLabel.RIGHT));
other = new JComboBox( );
centerPanel.add(other);
other.setEnabled(false);
centerPanel.add(new JLabel("Your choice:", JLabel.RIGHT));
centerPanel.add(choice = new JLabel( ));
JButton okButton;
cp.add(BorderLayout.SOUTH, okButton = new JButton("OK"));
okButton.addActionListener(new ActionListener( ) {
public void actionPerformed(ActionEvent e) {
PortChooser.this.dispose( );
}
});
}
/** Populate the ComboBoxes by asking the Java Communications API
* what ports it has. Since the initial information comes from
* a Properties file, it may not exactly reflect your hardware.
*/
protected void populate( ) {
// get list of ports available on this particular computer,
// by calling static method in CommPortIdentifier.
Enumeration pList = CommPortIdentifier.getPortIdentifiers( );
// Process the list, putting serial and parallel into ComboBoxes
while (pList.hasMoreElements( )) {
CommPortIdentifier cpi = (CommPortIdentifier)pList.nextElement( );
// System.out.println("Port " + cpi.getName( ));
map.put(cpi.getName( ), cpi);
if (cpi.getPortType( ) == CommPortIdentifier.PORT_SERIAL) {
serialPortsChoice.setEnabled(true);
serialPortsChoice.addItem(cpi.getName( ));
} else if (cpi.getPortType( ) == CommPortIdentifier.PORT_PARALLEL) {
parallelPortsChoice.setEnabled(true);
parallelPortsChoice.addItem(cpi.getName( ));
} else {
other.setEnabled(true);
other.addItem(cpi.getName( ));
}
}
serialPortsChoice.setSelectedIndex(-1);
parallelPortsChoice.setSelectedIndex(-1);
}
protected void finishGUI( ) {
serialPortsChoice.addItemListener(this);
parallelPortsChoice.addItemListener(this);
other.addItemListener(this);
pack( );
addWindowListener(new WindowCloser(this, true));
}
}