CS411X - Lecture 3

Lecture Topics:

• Progress Reports
• File Filter
• Images in Java
• Component class
• Sample Quiz

 
 Outline of your Progress Reports :

Date	Report #	version
02/20/97	1	Beta 1
03/07/97	2	Beta 2
03/21/97	3	Beta 3
04/10/97	4	Beta 4
04/21/97	5	final version 1.0
05/08/97	6	code with report

A Progress report should contain

a disk in an envelope
printouts & envelope stapled.

FileFilter.java

import java.io.*;
import java.util.*;
 
public class FileFilter implements FilenameFilter {
    public boolean accept(File dir, String name) {
        return new File(dir, name).isFile();
        }
}
 

DirFilter.java

import java.io.*;
import java.util.*;
 
public class DirFilter implements FilenameFilter {
    public boolean accept(File dir, String name) {
        return new File(dir, name).isDirectory();
    }
}
 

To Filter .java files ( The Java Filter )

JavaFilter.java

import java.io.*;
import java.util.*;
 
class JavaFilter implements FilenameFilter {
    public boolean accept(File dir, String name) {
        String match = ".java";
        int ml = match.length();
        int nl = name.length();
        if (nl > ml) {
            String post_fix = name.substring(nl - ml, nl);
            return post_fix.equals(match);
        }
        return false;
    }
}
 

Images in Java

Computer Vision

Rendering in Java :

• Built in Multi-threading
• Drawing in 2D
• supports paint and update ( Component methods )
• Image display

AWT Architecture

public void paint( Graphics g );

Who calls repaint( )?

Component method repaint( )

public void repaint( );

public void repaint( x, y, w, h );

public void repaint( t, x, y, w, h );

Component calls back : update( )

public void update( Graphics g );

• called in response to repaint( )
• background will not be cleared
• cliparea will be set to the repaint area
• default implemenetation clears the background and calls paint( )

callback paint( )

public void paint( Graphics g );

1. component first becomes visible
2. damage occurs

paint( ) and update( ) methods are called from the AWT callback thread.

public abstract class Graphics{

// you cannot make a graphics instance as a result
Graphics g = myPanel.getGraphics( );
g.dispose( );
 

Sample Quiz

• by calling its constructor directly from any package
• by calling its constructor within the package
• by calling the getGraphics( ) method of a component
• by calling the create( ) method directly
   

Last Update: 04/09/97
Copyright © 1997- Douglas Lyon
Lyon@cse.bridgeport.edu