Floating "boxes" applet with drag events need ckick events

Question

I Have an applet cobbled from the net & modified. Is works but needs one major event added. It draws "Graphics.drawline" boxes with a text "String" inside each box ( the text string represents an URL location). These "boxes" are objects which are "draggable to other locations on canvas & therefore can be independently positioned by user. Each box redraws itself periodically to a slightly different screen location & becomes stationary after a 5 or 6 seconds. The point is, all of this "drag & mobility" behavior must remain intact & is not part of the "problem task".
Task: Need to have an "event" behavior added in one of two ways ( or a 3rd way if there is another ) whichever is quickest/ easiest. "Clickable mouse events" must be added to each box. ( boxes are built in a loop so adding to one will add to other locations & create as many "buttons" as there are boxes) . At each box's location, clicking one box should be an event which fires & clicking a different box should be a separate event which fires. Separate , so that URL location can be "hotlinked" to each box. That URL is currently displayed in the boxes (visible when running applet).
1st possible solution: Exchange these "boxes" which appear on canvas into clickable event "Graph panel.buttons" ( for example or some other clickable object) which maintains existing "drag" behavior of boxes. These buttons must each have "clickability" with mouse events to enable placing "getAppletContext. showDocument()" code with these events ( e.g., "hotlinked" to http locations).
or
2nd possible solution:. The drawstring boxes are currently dead string text with no event model other than the "drag" feature associated with each box. Must add an additional mouse event behavior to existing boxes so they are "clickable" ( or text inside is clickable) and can then execute "showDocument()" URL when clicked independently.
Maybe there is a #3. I don't know what that would be. Open to try anything without losing the drag & placement mobility of existing boxes.
These "boxes" could be images, or event buttons - doesnt matter.
Not sure if #2 is possible & have not been able to accomplish #1. Must stay within existing AWT framework so IE browsers can run it natively ( which of course IE cannot run Swing graphics unless a Sun plugin loaded ).
Applet is a single file ( creating 4 classes).
html file (which invokes it) passes a string param which is broken into above noted URL strings in each box.
Running this applet, you see a "button" event ( at base of canvas labeled "NewUrl" ) which pops up an url location when clicked ( using "showdocument"). This button is not attached to locations or text of each box object ( which is the "task" to accomplish) . The button does represent the kind of event behavior which each "box" should have when task is achieved. So the box can be exchanged with buttons or the boxes can be imbued with events to hyperlink like a button.
In spirit of solution #1, here is the bonehead attempt I tried which did not work: copied entire "if" block of logic from the button event (sited in preceding paragraph) into region of code which builds boxes ( "for" loop of "drawstring" method).
"g.drawString(doit, x - (w-10)/2, (y - (h-4)/2) + fm.getAscent());"
I copied all the "if" block of logic for button creation into the area immediately after the above line ( for loop which builds the boxes). Hoping that I could create buttons with events, along with all the boxes (which are getting created using "drawstring" above in a "for" loop). These "buttons" must also have positioning info of each box to appear in different locations on the canvas. Positioning data is not in that "if" block of code but it would have been a start to get the multiple buttons created ( even if all drawn in one spot). The "if" code block I've provieded for an example begins with the line:
" if ("NewUrl".equals(arg)) { "
and ends with with lines:
" return true; "
" } " //< -- end of above if block
This full "if" block can be seen in the listing below:
This "if" block creates the "NewUrl" button. Of course, I got a bunch of errors when I tried to copy this block to the above location:
variable: "arg" "not found in class GraphPanel".
methods: "getcodebase, showstatus, getappletcontext()"
"not found in class GraphPanel".
----------- The applet code in total follows next
Here are both the java & htm complete source.
import java.net.MalformedURLException;
import java.net.URL;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.applet.Applet;
import java.applet.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.*;
class Node {
double x;
double y;
double dx;
double dy;
boolean fixed;
String lbl;
class Edge {
int from;
int to;
double len;
} // eEdgeCla
class GraphPanel extends Panel implements Runnable {
Box box;
int nnodes;
Node nodes[] = new Node[100];
int nedges;
Edge edges[] = new Edge[200];
Thread relaxer;
boolean showit;
boolean random;
GraphPanel(Box box) {
this.box = box;
} //ebox
int findNode(String lbl) {
for (int i = 0 ; i < nnodes ; i++) {
if (nodes.lbl.equals(lbl)) {
return i;
return addNode(lbl);
int addNode(String lbl) {
Node n = new Node();
n.x = 10 + 380*Math.random();
n.y = 10 + 380*Math.random();
n.lbl = lbl;
nodes[nnodes] = n;
return nnodes++;
void addEdge(String from, String to, int len) {
Edge e = new Edge();
e.from = findNode(from);
e.to = findNode(to);
e.len = len;
edges[nedges++] = e;
public void run() {
int i3=0;
while (true) {
relax();
if (random && (Math.random() < 0.03)) {
Node n = nodes[(int) (1 * nnodes) ]; // no
if (!n.fixed) {
n.x += (100*0.02) - 50;
n.y += (100*0.02) - 50; //
try {
Thread.sleep(4000);
} catch (InterruptedException e) {
break;
i3++;
} //ew
} // epublrun()
synchronized void relax() {
for (int i = 0 ; i < nedges ; i++) {
Edge e = edges;
double vx = nodes[e.to].x - nodes[e.from].x;
double vy = nodes[e.to].y - nodes[e.from].y;
double len = Math.sqrt(vx * vx + vy * vy);
double f = (edges.len - len) / (len * 3) ;
double dx = f * vx;
double dy = f * vy;
nodes[e.to].dx += dx;
nodes[e.to].dy += dy;
nodes[e.from].dx += -dx;
nodes[e.from].dy += -dy;
} //efo
for (int i = 0 ; i < nnodes ; i++) {
Node n1 = nodes;
double dx = 0;
double dy = 0;
for (int j = 0 ; j < nnodes ; j++) {
if (i == j) {
continue;
Node n2 = nodes[j];
double vx = n1.x - n2.x;
double vy = n1.y - n2.y;
double len = vx * vx + vy * vy;
if (len == 0) {
dx += 0.02;
dy += 0.02;
} else if (len < 100*100) {
dx += vx / len;
dy += vy / len;
} //ef3a
double dlen = dx * dx + dy * dy;
if (dlen > 0) {
dlen = Math.sqrt(dlen) / 2;
n1.dx += dx / dlen;
n1.dy += dy / dlen;
} //ef3
Dimension d = size();
// f4
for (int i = 0 ; i < nnodes ; i++) {
Node n = nodes;
if (!n.fixed) {
n.x += Math.max(-5, Math.min(5, n.dx));
n.y += Math.max(-5, Math.min(5, n.dy));
if (n.x < 0) {
n.x = 0;
} else if (n.x > d.width) {
n.x = d.width;
if (n.y < 0) {
n.y = 0;
} else if (n.y > d.height) {
n.y = d.height;
n.dx /= 2;
n.dy /= 2;
repaint();
Node pick;
boolean pickfixed;
Image offscreen;
Dimension offscreensize;
Graphics offgraphics;
final Color fixedColor = Color.green;
final Color selectColor = Color.gray;
final Color edgeColor = Color.black;
final Color nodeColor = new Color(200, 90, 50);
final Color showitColor = Color.gray;
final Color arcColor1 = Color.black;
final Color arcColor2 = Color.orange;
final Color arcColor3 = Color.blue;
public void paintNode( Graphics g, Node n, FontMetrics fm) {
int x = (int)n.x;
int y = (int)n.y;
g.setColor((n == pick) ? selectColor : (n.fixed ? fixedColor : nodeColor));
int w = fm.stringWidth(n.lbl) + 10;
int h = fm.getHeight() + 4;
g.fillRect(x - w/2, y - h / 2, w, h);
g.setColor(Color.black);
g.drawRect(x - w/2, y - h / 2, w-1, h-1);
String doit = n.lbl.replace('x','/');
g.drawString(doit, x - (w-10)/2, (y - (h-4)/2) + fm.getAscent());
} // epa
public synchronized void update(Graphics g) {
Dimension d = size();
if ((offscreen == null) || (d.width != offscreensize.width) || (d.height != offscreensize.height)) {
offscreen = createImage(d.width, d.height);
offscreensize = d;
offgraphics = offscreen.getGraphics();
offgraphics.setFont(getFont());
offgraphics.setColor(getBackground());
offgraphics.fillRect(0, 0, d.width, d.height);
for (int i = 0 ; i < nedges ; i++) {
Edge e = edges;
int x1 = (int)nodes[e.from].x;
int y1 = (int)nodes[e.from].y;
int x2 = (int)nodes[e.to].x;
int y2 = (int)nodes[e.to].y;
int len = (int)Math.abs(Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)) - e.len);
offgraphics.setColor((len < 10) ? arcColor1 : (len < 20 ? arcColor2 : arcColor3)) ;
offgraphics.drawLine(x1, y1, x2, y2);
if (showit) {
String lbl = String.valueOf(len);
offgraphics.setColor(showitColor);
offgraphics.drawString("href= http://localhost:"+lbl, x1 + (x2-x1)/2, y1 + (y2-y1)/2);
offgraphics.setColor(edgeColor);
} //ef5
FontMetrics fm = offgraphics.getFontMetrics();
for (int i = 0 ; i < nnodes ; i++) {
paintNode( offgraphics, nodes, fm); //or
g.drawImage(offscreen, 0, 0, null);
public synchronized boolean mouseDown(Event evt, int x, int y) {
double bestdist = Double.MAX_VALUE;
for (int i = 0 ; i < nnodes ; i++) {
Node n = nodes;
double dist = (n.x - x) * (n.x - x) + (n.y - y) * (n.y - y);
if (dist < bestdist) {
pick = n;
bestdist = dist;
pickfixed = pick.fixed;
pick.fixed = true;
pick.x = x;
pick.y = y;
repaint();
return true;
public synchronized boolean mouseDrag(Event evt, int x, int y) {
pick.x = x;
pick.y = y;
repaint();
return true;
} //e-pubsyncmousedrag
public synchronized boolean mouseUp(Event evt, int x, int y) {
pick.x = x;
pick.y = y;
pick.fixed = pickfixed;
pick = null;
repaint();
return true;
public void start() {
relaxer = new Thread(this);
relaxer.start();
public void stop() {
relaxer.stop();
public class Box extends Applet {
GraphPanel panel;
public void init() {
setLayout(new BorderLayout());
panel = new GraphPanel(this);
add("Center", panel);
Panel p = new Panel();
add("South", p);
p.add(new Button("Reposition"));
p.add(new Button("NewUrl"));
p.add(new Checkbox("Showit"));
String edges = getParameter("edges"); // putinli
for (StringTokenizer t = new StringTokenizer(edges, ",") ; t.hasMoreTokens() ; ) {
String str = t.nextToken();
int i = str.indexOf('-');
if (i > 0) { int len = 50;
int j = str.indexOf('/');
if (j > 0) {
len = Integer.valueOf(str.substring(j+1)).intValue();
str = str.substring(0, j);
panel.addEdge(str.substring(0,i), str.substring(i+1), len);
} //ef8
Dimension d = size();
String center = getParameter("center");
if (center != null){
Node n = panel.nodes[panel.findNode(center)];
n.x = d.width / 2;
n.y = d.height / 2;
n.fixed = true;
} // eif
} // ep
public void start() {
panel.start();
public void stop() {
panel.stop();
public boolean action(Event evt, Object arg) {
if (arg instanceof Boolean) {
if (((Checkbox)evt.target).getLabel().equals("Showit")) {
panel.showit = ((Boolean)arg).booleanValue();
}// e-
else {
panel.random = ((Boolean)arg).booleanValue();
return true;
} // e-if instof bool
if ("Reposition".equals(arg)) {
Dimension d = size();
for (int i = 0 ; i < panel.nnodes ; i++) {
Node n = panel.nodes;
if (!n.fixed) {
n.x = 10 + (d.width-20)*Math.random();
n.y = 10 + (d.height-20)*Math.random();
} //ei
} //ef9
return true;
} //eif scram
if ("NewUrl".equals(arg)) {
Dimension d = size();
URL url = getCodeBase();
try {
getAppletContext().showDocument( new URL(url+"main.htm"), "_blank" );
try {
Thread.sleep(1000);
} catch (InterruptedException e) { }
} catch(MalformedURLException e) {
showStatus("814 URL not found");
for (int i = 0 ; i < panel.nnodes ; i++) {
Node n = panel.nodes;
if (!n.fixed) {
n.x += (80*0.02) - 40;
n.y += (80*0.02) - 40;
return true;
} //ei
return false;
-----------------------htm file to launch------------------------------
<html>
<head>
<title>R
</title>
</head>
<body>
<h3>
<center>
R
</center>
</h3>
I
<b>
</b>
<table border = 1>
<td>De<td>Test List<tr>
<td>N <td><tr>
<td>N <td><tr>
</table>
<b>view </b>
<applet code="Box.class" CODEBASE=. width=1000 height=600
ALT="Test ">
<param name=edges value="http:xxabc.htm-http:xxnet.htm,http:xxthis.htm-http:xx.comet.htm,http:xxnewsighting.htm-http:xxstar.htm,http:xxmoon.htm-http:xxNeptune.htm">
<hr>
</applet>
</b>
<p>
<table border = 1>
<tr>
<tr>
</table>
</html>
</body>
instructions to compile :
0 : The discussion becomes easy to follow after 1st compiling
& viewing the applet.
1. : cut out applet code.
2. : the post somehow deleted all references to "" <--- HERE
see, the data has been deleted again as I preview this post.
( that "" should contain an "i" array increment argument:
"open square bracket" "i" "close square bracket" ) array
so "javac Box.java" will get 10 errors. These "[" "i" "]"
array args must be replaced to compile the code.
3. : All array variables inside the 10 "for" loops ( the bare words
"edges" and "nodes" ) without array increment "i" should
read "edges" "[" "i" "]" & "nodes" "[" "i" "]".
The 10 location lines are approx:
line #65, #129, #136, #149, #195, #283, #311, #331, #477, #522
4. : These 10 edits reqresent a missing "i" to all 10 for loop arrays.
for eddges & nodes. fix this & javac Box.java" will get
4 class files.
5. : cut "Box.htm" from post & do "appletviewer Box.htm"
or put in an apache "htdoc" or tomcat "servlet" http delivered
directory & call "http://localhost/Box.htm.
6. : of course, selecting the event button "NewUrl" will not
work in appletviewer but will work in an http web location.
7. : post your questions to problem or fixes to problem as I'm
monitoring closely. TIA.

Answer 1

Thanks for code post tip to fix array index deletion problem.
Here is code reposted using "code" delimiters which will
compile straight out of cut/paste.
import java.net.MalformedURLException;
import java.net.URL;
import java.net.*;
import java.util.*;
import java.awt.*;
import java.applet.Applet;
import java.applet.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.*;
class Node {
double x;
double y;
double dx;
double dy;
boolean fixed;
String lbl;
class Edge {
int from;
int to;
double len;
} // eEdgeCla
class GraphPanel extends Panel implements Runnable {
Box box;
int nnodes;
Node nodes[] = new Node[100];
int nedges;
Edge edges[] = new Edge[200];
Thread relaxer;
boolean showit;
boolean random;
GraphPanel(Box box) {
this.box = box;
} //ebox
int findNode(String lbl) {
for (int i = 0 ; i < nnodes ; i++) {
//if (nodes.lbl.equals(lbl)) {
  if (nodes.lbl.equals(lbl)) {
return i;
return addNode(lbl);
int addNode(String lbl) {
Node n = new Node();
n.x = 10 + 380*Math.random();
n.y = 10 + 380*Math.random();
n.lbl = lbl;
nodes[nnodes] = n;
return nnodes++;
void addEdge(String from, String to, int len) {
Edge e = new Edge();
e.from = findNode(from);
e.to = findNode(to);
e.len = len;
edges[nedges++] = e;
public void run() {
int i3=0;
while (true) {
relax();
if (random && (Math.random() < 0.03)) {
Node n = nodes[(int) (1 * nnodes) ]; // no
if (!n.fixed) {
n.x += (100*0.02) - 50;
n.y += (100*0.02) - 50; //
try {
Thread.sleep(4000);
} catch (InterruptedException e) {
break;
i3++;
} //ew
} // epublrun()
synchronized void relax() {
for (int i = 0 ; i < nedges ; i++) {
//Edge e = edges;
Edge e = edges[i];
double vx = nodes[e.to].x - nodes[e.from].x;
double vy = nodes[e.to].y - nodes[e.from].y;
double len = Math.sqrt(vx * vx + vy * vy);
//double f = (edges.len - len) / (len * 3) ;
double f = (edges[i].len - len) / (len * 3) ;
double dx = f * vx;
double dy = f * vy;
nodes[e.to].dx += dx;
nodes[e.to].dy += dy;
nodes[e.from].dx += -dx;
nodes[e.from].dy += -dy;
} //efo
for (int i = 0 ; i < nnodes ; i++) {
//Node n1 = nodes[i];
Node n1 = nodes[i];
double dx = 0;
double dy = 0;
for (int j = 0 ; j < nnodes ; j++) {
if (i == j) {
continue;
Node n2 = nodes[j];
double vx = n1.x - n2.x;
double vy = n1.y - n2.y;
double len = vx * vx + vy * vy;
if (len == 0) {
dx += 0.02;
dy += 0.02;
} else if (len < 100*100) {
dx += vx / len;
dy += vy / len;
} //ef3a
double dlen = dx * dx + dy * dy;
if (dlen > 0) {
dlen = Math.sqrt(dlen) / 2;
n1.dx += dx / dlen;
n1.dy += dy / dlen;
} //ef3
Dimension d = size();
// f4
for (int i = 0 ; i < nnodes ; i++) {
//Node n = nodes;
Node n = nodes[i];
if (!n.fixed) {
n.x += Math.max(-5, Math.min(5, n.dx));
n.y += Math.max(-5, Math.min(5, n.dy));
if (n.x < 0) {
n.x = 0;
} else if (n.x > d.width) {
n.x = d.width;
if (n.y < 0) {
n.y = 0;
} else if (n.y > d.height) {
n.y = d.height;
n.dx /= 2;
n.dy /= 2;
repaint();
Node pick;
boolean pickfixed;
Image offscreen;
Dimension offscreensize;
Graphics offgraphics;
final Color fixedColor = Color.green;
final Color selectColor = Color.gray;
final Color edgeColor = Color.black;
final Color nodeColor = new Color(200, 90, 50);
final Color showitColor = Color.gray;
final Color arcColor1 = Color.black;
final Color arcColor2 = Color.orange;
final Color arcColor3 = Color.blue;
public void paintNode( Graphics g, Node n, FontMetrics fm) {
int x = (int)n.x;
int y = (int)n.y;
g.setColor((n == pick) ? selectColor : (n.fixed ? fixedColor : nodeColor));
int w = fm.stringWidth(n.lbl) + 10;
int h = fm.getHeight() + 4;
g.fillRect(x - w/2, y - h / 2, w, h);
g.setColor(Color.black);
g.drawRect(x - w/2, y - h / 2, w-1, h-1);
String doit = n.lbl.replace('x','/');
g.drawString(doit, x - (w-10)/2, (y - (h-4)/2) + fm.getAscent());
} // epa
public synchronized void update(Graphics g) {
Dimension d = size();
if ((offscreen == null) || (d.width != offscreensize.width) || (d.height != offscreensize.height)) {
offscreen = createImage(d.width, d.height);
offscreensize = d;
offgraphics = offscreen.getGraphics();
offgraphics.setFont(getFont());
offgraphics.setColor(getBackground());
offgraphics.fillRect(0, 0, d.width, d.height);
for (int i = 0 ; i < nedges ; i++) {
//Edge e = edges;
Edge e = edges[i];
int x1 = (int)nodes[e.from].x;
int y1 = (int)nodes[e.from].y;
int x2 = (int)nodes[e.to].x;
int y2 = (int)nodes[e.to].y;
int len = (int)Math.abs(Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)) - e.len);
offgraphics.setColor((len < 10) ? arcColor1 : (len < 20 ? arcColor2 : arcColor3)) ;
offgraphics.drawLine(x1, y1, x2, y2);
if (showit) {
String lbl = String.valueOf(len);
offgraphics.setColor(showitColor);
offgraphics.drawString("href= http://localhost:"+lbl, x1 + (x2-x1)/2, y1 + (y2-y1)/2);
offgraphics.setColor(edgeColor);
} //ef5
FontMetrics fm = offgraphics.getFontMetrics();
for (int i = 0 ; i < nnodes ; i++) {
//paintNode( offgraphics, nodes, fm); //or
paintNode( offgraphics, nodes[i], fm); //or
g.drawImage(offscreen, 0, 0, null);
public synchronized boolean mouseDown(Event evt, int x, int y) {
double bestdist = Double.MAX_VALUE;
for (int i = 0 ; i < nnodes ; i++) {
//Node n = nodes;
Node n = nodes[i];
double dist = (n.x - x) * (n.x - x) + (n.y - y) * (n.y - y);
if (dist < bestdist) {
pick = n;
bestdist = dist;
pickfixed = pick.fixed;
pick.fixed = true;
pick.x = x;
pick.y = y;
repaint();
return true;
public synchronized boolean mouseDrag(Event evt, int x, int y) {
pick.x = x;
pick.y = y;
repaint();
return true;
} //e-pubsyncmousedrag
public synchronized boolean mouseUp(Event evt, int x, int y) {
pick.x = x;
pick.y = y;
pick.fixed = pickfixed;
pick = null;
repaint();
return true;
public void start() {
relaxer = new Thread(this);
relaxer.start();
public void stop() {
relaxer.stop();
public class Box extends Applet {
GraphPanel panel;
public void init() {
setLayout(new BorderLayout());
panel = new GraphPanel(this);
add("Center", panel);
Panel p = new Panel();
add("South", p);
p.add(new Button("Reposition"));
p.add(new Button("NewUrl"));
p.add(new Checkbox("Showit"));
String edges = getParameter("edges"); // putinli
for (StringTokenizer t = new StringTokenizer(edges, ",") ; t.hasMoreTokens() ; ) {
String str = t.nextToken();
int i = str.indexOf('-');
if (i > 0) { int len = 50;
int j = str.indexOf('/');
if (j > 0) {
len = Integer.valueOf(str.substring(j+1)).intValue();
str = str.substring(0, j);
panel.addEdge(str.substring(0,i), str.substring(i+1), len);
} //ef8
Dimension d = size();
String center = getParameter("center");
if (center != null){
Node n = panel.nodes[panel.findNode(center)];
n.x = d.width / 2;
n.y = d.height / 2;
n.fixed = true;
} // eif
} // ep
public void start() {
panel.start();
public void stop() {
panel.stop();
public boolean action(Event evt, Object arg) {
if (arg instanceof Boolean) {
if (((Checkbox)evt.target).getLabel().equals("Showit")) {
panel.showit = ((Boolean)arg).booleanValue();
}// e-
else {
panel.random = ((Boolean)arg).booleanValue();
return true;
} // e-if instof bool
if ("Reposition".equals(arg)) {
Dimension d = size();
for (int i = 0 ; i < panel.nnodes ; i++) {
//Node n = panel.nodes;
Node n = panel.nodes[i];
if (!n.fixed) {
n.x = 10 + (d.width-20)*Math.random();
n.y = 10 + (d.height-20)*Math.random();
} //ei
} //ef9
return true;
} //eif scram
if ("NewUrl".equals(arg)) {
Dimension d = size();
URL url = getCodeBase();
try {
getAppletContext().showDocument( new URL(url+"main.htm"), "_blank" );
try {
Thread.sleep(1000);
} catch (InterruptedException e) { }
} catch(MalformedURLException e) {
showStatus("814 URL not found");
for (int i = 0 ; i < panel.nnodes ; i++) {
//Node n = panel.nodes;
Node n = panel.nodes[i];
if (!n.fixed) {
n.x += (80*0.02) - 40;
n.y += (80*0.02) - 40;
return true;
} //ei
return false;