NewsScroller: WebBase.java
package crackers.Scroller;
/**
* A super-class for animated applets. This class contains many standard methods
* and parameters * for providing simple animation using double-buffering (where
* the image is drawn "off-screen" and then drawn all at one time to the
* receiving Graphics object.
* <P>
* This program is copyrighted 1999 by the author under the GNU Public License
* (GPL). Full text of this license is available at
* <A HREF="http://www.gnu.org">GNU.org</A>.
* <P>
* For full usage information, see
* <A HREF="http://www.io.com/~crackers">my web pages</A>.
*
* @author E. A. Graham, Jr. (crackers@io.com)
* @version 2.0
*/
import java.awt.*;
import java.applet.*;
import java.net.URL;
import java.net.MalformedURLException;
public abstract class WebBase extends Applet implements Runnable
{
/**
* Default sleep time (milliseconds).
*/
private final int DEFAULT_SLEEP = 150;
/**
* Default scroll increment (pixels).
*/
private final int DEFAULT_SCROLL = 10;
/**
* The animation thread.
*/
protected Thread myThread = null;
/**
* Maximum width of the graphics image.
*/
protected int maxWidth;
/**
* Maximum height of the graphics image.
*/
protected int maxHeight;
/**
* Width of the border on the image.
*/
protected int borderWidth;
/**
* The increment to advance the animation (pixels).
*/
protected int scrollUnit;
/**
* The amount of time (ms) to wait between updates.
* Can be considered to be the "frame-rate" of the animation.
*/
protected long sleepTime;
/**
* The off-screen image to draw to.
*/
protected Image appImage;
/**
* The graphics object for the off-screen image.
*/
protected Graphics appGC;
/**
* The foreground color to use while drawing the image.
*/
protected Color foreColor;
/**
* The background color to use while drawing the image.
*/
protected Color backColor;
/**
* An internal flag to indicate whether or not the
* animation thread is running.
*/
protected boolean loaded = false;
/**
* The image object for the background graphics, if used.
*/
protected Image backgroundImage = null;
/**
* An HTML frame "target" parameter, if used.
*/
protected String frameTarget = null;
/**
* Applet initialization.
*/
public void init()
{
// get the size of the applet
Dimension d = getSize();
maxWidth = d.width;
maxHeight = d.height;
// used for children of this class to target URL jumps
// defaults to "_top"
frameTarget = readParam("TARGET","_top");
// get some numeric parameters
sleepTime = readLong("SleepTime",DEFAULT_SLEEP);
scrollUnit = readInteger("ScrollBy",DEFAULT_SCROLL);
borderWidth = readInteger("BORDER",0);
// the color parameters
foreColor = readColor("FOREGROUND",Color.black);
backColor = readColor("BACKGROUND",Color.white);
setBackground(backColor);
// a background picture (go ahead and wait for full load)
String tparam = readParam("PICTURE",null);
if (tparam != null)
{
MediaTracker imgTrack;
URL theURL = null;
try
{
// get the image url
if (tparam.indexOf("http://") >= 0 )
theURL = new URL(tparam);
else
theURL = new URL(getDocumentBase(),tparam);
// load the image
backgroundImage = getImage(theURL);
if (backgroundImage != null)
{
imgTrack = new MediaTracker(this);
imgTrack.addImage(backgroundImage,0);
imgTrack.waitForAll();
if (imgTrack.isErrorAny())
backgroundImage = null;
}
}
catch (Exception e)
{
backgroundImage = null;
}
}
appImage = createImage(maxWidth, maxHeight);
appGC = appImage.getGraphics();
}
/**
* Read an HTML-supplied parameter.
* @param param the HTML PARAM tag to find
* @param defaultValue the default value to return if the parameter is not
* found.
* @return the String of the parameter or the defaultValue on error
*/
protected String readParam(String param,String defaultValue)
{
String rtn = null;
try
{
rtn = getParameter(param);
}
catch (Exception e) { }
if (rtn == null) rtn = defaultValue;
return rtn;
}
/**
* Read an HTML-supplied parameter.
* @param param the HTML PARAM tag to find
* @return the String of the parameter, or null on error
*/
protected String readParam(String param)
{
return readParam(param,null);
}
/**
* Read an HTML-supplied parameter as an integer.
* @param param the HTML PARAM tag to find
* @param defaultValue the default value
* @return the parameter or the default value if no parameter
*/
protected int readInteger(String param, int defaultValue)
{
try
{
String s = readParam(param);
int x = Integer.parseInt(s);
return x;
}
catch (Exception e)
{
return defaultValue;
}
}
/**
* Read an HTML-supplied parameter as a long.
* @param param the HTML PARAM tag to find
* @param defaultValue the default value
* @return the parameter or the default value if no parameter
*/
protected long readLong(String param, long defaultValue)
{
try
{
String s = readParam(param);
long x = Long.parseLong(s);
return x;
}
catch (Exception e)
{
return defaultValue;
}
}
/**
* Reads a color HTML-supplied parameter (either R,G,B or hex RGB value).
* @param param name of the parameter to read
* @param defColor default color to use if no parameter present or is
* an invalid format
* @return a Color corresponding to the parameter string.
* @see readParam
*/
protected Color readColor(String sParam, Color defColor)
{
String tparam = readParam(sParam);
Color tcolor;
int rc,gc,bc;
// set the component colors to invalid values
rc = gc = bc = -1;
// a parameter was used...
if (tparam != null)
{
// looks like it might be "HTML" format
if (tparam.startsWith("#"))
{
// if it's the right length, try to separate it properly
if (tparam.length()==7)
{
try
{
rc = Integer.parseInt(tparam.substring(1,3),16);
gc = Integer.parseInt(tparam.substring(3,5),16);
bc = Integer.parseInt(tparam.substring(5),16);
}
catch (Exception e) { }
}
}
// not "HTML" format: try to separate it as CSV
else
{
int x,y;
x = tparam.indexOf(',');
y = tparam.lastIndexOf(',');
if (x>0 && y>0 && x!=y)
{
try
{
rc = Integer.parseInt(tparam.substring(0,x));
gc = Integer.parseInt(tparam.substring(x+1,y));
bc = Integer.parseInt(tparam.substring(y+1));
}
catch (Exception e) { }
}
}
}
// try to make a new color with the three RGB values, or get the
// default
tcolor = (rc>=0 && rc<=255 && gc>=0 && gc<=255 && bc>=0 && bc<=255) ? new Color(rc,gc,bc) : defColor;
return (tcolor);
}
/**
* Start the applet thread. Initialize the animation thread.
*/
public void start()
{
if (myThread == null)
{
myThread = new Thread(this);
myThread.start();
}
loaded = true;
}
/**
* Stop the applet thread. If the animation thread is alive, kill it.
*/
public void stop()
{
if ((myThread != null) && myThread.isAlive())
myThread.stop();
loaded = false;
myThread = null;
}
/**
* The main thread method.
* @see java.lang.Runnable
*/
public void run()
{
// get which is the current thread and set a low priority on it
Thread me = Thread.currentThread();
me.setPriority(Thread.MIN_PRIORITY);
// craete a blank image and it's Graphic object
appImage = createImage(maxWidth, maxHeight);
appGC = appImage.getGraphics();
// force an early paint, even though we haven't actually drawn anything
// to paint, yet
repaint();
// while we have a hold of the animation thread...
while (myThread == me)
{
// just to make sure the applet is running
if (loaded)
{
// do our thing, repaint, and go to sleep
doAppThing();
repaint();
try
{
Thread.sleep(sleepTime);
}
catch(InterruptedException e){}
}
}
}
/**
* Sub-classes must implement this method. This method is where the
* sub-classes will update the image to be painted.
* @see update
*/
protected abstract void doAppThing();
/**
* Over-ride of the superclass method. Because the acutal painting takes
* place in the update method, we don't want any painting to occur here.
*/
public void paint(Graphics g)
{ }
/**
* Over-ride of the superclass method. Draws all of the current elements
* onto the visible Graphics object of the applet. Sub-classes will also
* over-ride this method to supply their own implementations.
* @param g the Graphics object to update
*/
public synchronized void update(Graphics g)
{
// the animation is running
if (loaded)
{
// if there's a background picture, use it
if (backgroundImage != null)
appGC.drawImage(backgroundImage,0, 0, maxWidth, maxHeight,this);
// otherwise, draw background rectangle...
else
{
appGC.setColor(backColor);
appGC.fillRect(0, 0, maxWidth, maxHeight);
}
}
}
/**
* Draws a 3-D border on the applet image Graphics object.
* Uses the width, height, and BORDER parameter to determine the wheres and
* whats of how to draw the border.
*/
protected void drawBorder()
{
if (borderWidth == 0) return;
Color bc_light,bc_dark;
int pWidth = Math.abs(borderWidth);
Polygon bp_below = new Polygon();
Polygon bp_above = new Polygon();
// if the background is white, we can't make the border lighter, so we
// come up with two darker colors
if (backColor.equals(Color.white))
{
bc_light = backColor.darker();
bc_dark = bc_light.darker();
}
else if (backColor.equals(Color.black))
{
bc_light = Color.gray;
bc_dark = Color.gray.darker();
}
else
{
bc_light = backColor.brighter();
bc_dark = backColor.darker();
}
// add the vertices to the polygons
bp_above.addPoint(0,0);
bp_above.addPoint(maxWidth,0);
bp_above.addPoint(maxWidth-pWidth,pWidth);
bp_above.addPoint(pWidth,pWidth);
bp_above.addPoint(pWidth,maxHeight-pWidth);
bp_above.addPoint(0,maxHeight);
bp_below.addPoint(maxWidth,0);
bp_below.addPoint(maxWidth,maxHeight);
bp_below.addPoint(0,maxHeight);
bp_below.addPoint(pWidth,maxHeight-pWidth);
bp_below.addPoint(maxWidth-pWidth,maxHeight-pWidth);
bp_below.addPoint(maxWidth-pWidth,pWidth);
// draw the polygons with appropriate colors
appGC.setColor(borderWidth < 0 ? bc_dark : bc_light);
appGC.fillPolygon(bp_above);
appGC.setColor(borderWidth < 0 ? bc_light : bc_dark);
appGC.fillPolygon(bp_below);
}
}
Index
New on the Java Boutique:
New Review:
Time Management Made Easy with the Quartz Enterprise Job Scheduler
Why not just use the Java timer API? This open source scheduling
API boasts simplicity, ease-of-integration, a well-rounded feature
set, and it's free!
New Applet:
Reverse Complement
Reverse Complement is a simple applet that converts DNA or RNA
sequences into three useful formats.
Elsewhere on internet.com:
WebDeveloper Java
Lots of Java information on webdeveloper.com
WDVL Java
Thorough Java resource at the Web Developer's Virtual Library.
ScriptSearch Java
Hundreds of free Java code files to download.
jGuru: Your View of the Java Universe
Customizable portal with online training, FAQs, regular news updates, and tutorials.
|
