␡
- Goals and Assumptions
- Design the Program
- Write the Source Code
- Compile the Source Code
- Run the Program
- Conclusion
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Write the Source Code
And now for the moment of truth: We must convert the pseudo-code to Java source code. Listing 2 presents this source code.
Listing 2 The MediaPlayer application source code
// MediaPlayer.java
import javax.media.*;
import java.awt.*;
import java.awt.event.*;
class MediaPlayer extends Frame implements ActionListener,
ControllerListener,
ItemListener
{
Player player;
Component vc, cc;
boolean first = true, loop = false;
String currentDirectory;
MediaPlayer (String title)
{
super (title);
addWindowListener
(new WindowAdapter ()
{
public void windowClosing (WindowEvent e)
{
// User selected close from System menu.
// Call dispose to invoke windowClosed.
dispose ();
}
public void windowClosed (WindowEvent e)
{
if (player != null)
player.close ();
System.exit (0);
}
});
Menu m = new Menu ("File");
MenuItem mi = new MenuItem ("Open...");
mi.addActionListener (this);
m.add (mi);
m.addSeparator ();
CheckboxMenuItem cbmi = new CheckboxMenuItem ("Loop", false);
cbmi.addItemListener (this);
m.add (cbmi);
m.addSeparator ();
mi = new MenuItem ("Exit");
mi.addActionListener (this);
m.add (mi);
MenuBar mb = new MenuBar ();
mb.add (m);
setMenuBar (mb);
setSize (200, 200);
setVisible (true);
}
public void actionPerformed (ActionEvent e)
{
if (e.getActionCommand ().equals ("Exit"))
{
// Call dispose to invoke windowClosed.
dispose ();
return;
}
FileDialog fd = new FileDialog (this, "Open File",
FileDialog.LOAD);
fd.setDirectory (currentDirectory);
fd.show ();
// If user cancelled, exit.
if (fd.getFile () == null)
return;
currentDirectory = fd.getDirectory ();
if (player != null)
player.close ();
try
{
player = Manager.createPlayer (new MediaLocator
("file:" +
fd.getDirectory () +
fd.getFile ()));
}
catch (java.io.IOException e2)
{
System.out.println (e2);
return;
}
catch (NoPlayerException e2)
{
System.out.println ("Could not find a player.");
return;
}
if (player == null)
{
System.out.println ("Trouble creating a player.");
return;
}
first = false;
setTitle (fd.getFile ());
player.addControllerListener (this);
player.prefetch ();
}
public void controllerUpdate (ControllerEvent e)
{
// A ControllerClosedEvent is posted when player.close is
// called. If there is a visual component, this component must
// be removed. Otherwise, this visual component appears
// blanked out on the screen. (To be consistent, we do the same
// thing for the control panel component.)
//
// Note: This problem occurs when run under JMF 2.1 Windows and
// SDK 1.3 on a Windows 98 SE platform.
if (e instanceof ControllerClosedEvent)
{
if (vc != null)
{
remove (vc);
vc = null;
}
if (cc != null)
{
remove (cc);
cc = null;
}
return;
}
if (e instanceof EndOfMediaEvent)
{
if (loop)
{
player.setMediaTime (new Time (0));
player.start ();
}
return;
}
if (e instanceof PrefetchCompleteEvent)
{
player.start ();
return;
}
if (e instanceof RealizeCompleteEvent)
{
vc = player.getVisualComponent ();
if (vc != null)
add (vc);
cc = player.getControlPanelComponent ();
if (cc != null)
add (cc, BorderLayout.SOUTH);
pack ();
}
}
public void itemStateChanged (ItemEvent e)
{
loop = !loop;
}
public void paint (Graphics g)
{
if (first)
{
int w = getSize ().width;
int h = getSize ().height;
g.setColor (Color.blue);
g.fillRect (0, 0, w, h);
Font f = new Font ("DialogInput", Font.BOLD, 16);
g.setFont (f);
FontMetrics fm = g.getFontMetrics ();
int swidth = fm.stringWidth ("*** Welcome ***");
g.setColor (Color.white);
g.drawString ("*** Welcome ***",
(w - swidth) / 2,
(h + getInsets ().top) / 2);
}
// Call overridden Frame superclass paint method. That method
// will call each contained container and component (including
// the control panel component) paint method.
super.paint (g);
}
// Eliminate control panel component flicker by preventing frame
// background from being cleared.
public void update (Graphics g)
{
paint (g);
}
public static void main (String [] args)
{
new MediaPlayer ("Media Player 1.0");
}
}
I won't perform a detailed analysis of this source code because it already contains documentation comments that explain why certain things are being done. Furthermore, the previous pseudo-code, which closely mimics this source code, already provides a detailed analysis of how the program works.
Before you can build the media player, you need to copy its source code to a file. You can choose whatever name you want for this file (although I've chosen MediaPlayer.java). However, make sure that your filename ends in a .java file extension.