Applet应用程序为什么不能在Eclipse里面运行
1.在web上面运行是这样的.
2.在Eclipse里面运行是这样的.
3.下面是代码
4.问题：是不是要自己创建显示图形extend JFrame什么的?程序报空指针异常,未初始化实在弄不明白。如何在Eclipse里面显示出来？
package example;Eclipse Applet 应用
class Node {
double x,y,dx,dy;
boolean fixed;
String lbl;
}
class Edge {
int from,to;
double len;
}
class GraphPanel extends Panel
implements Runnable, MouseListener, MouseMotionListener {
Graph graph;
int nnodes;
Node nodes[] = new Node[100];
int nedges;
Edge edges[] = new Edge[200];
Thread relaxer,stress;
boolean random;
int numMouseButtonsDown = 0;
GraphPanel(Graph graph) {
this.graph = graph;
addMouseListener(this);
}
int findNode(String lbl) {
for (int i = 0 ; i < nnodes ; i++) {
if (nodes[i].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() {
Thread me = Thread.currentThread();
while (relaxer == me) {
relax();
if (random && (Math.random() < 0.03)) {
Node n = nodes[(int)(Math.random() * nnodes)];
if (!n.fixed) {
n.x += 100*Math.random() - 50;
n.y += 100*Math.random() - 50;
}
graph.play(graph.getCodeBase(), "audio/drip.au");
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
break;
}
}
}
synchronized void relax() {
for (int i = 0 ; i < nedges ; i++) {
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);
len = (len == 0) ? .0001 : len;
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;
}
for (int i = 0 ; i < nnodes ; 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 += Math.random();
dy += Math.random();
} else if (len < 100*100) {
dx += vx / len;
dy += vy / len;
}
}
double dlen = dx * dx + dy * dy;
if (dlen > 0) {
dlen = Math.sqrt(dlen) / 2;
n1.dx += dx / dlen;
n1.dy += dy / dlen;
}
}
Dimension d = getSize();
for (int i = 0 ; i < nnodes ; i++) {
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.red;
final Color selectColor = Color.pink;
final Color edgeColor = Color.black;
final Color nodeColor = new Color(250, 220, 100);
final Color stressColor = Color.darkGray;
final Color arcColor1 = Color.black;
final Color arcColor2 = Color.pink;
final Color arcColor3 = Color.red;
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);
g.drawString(n.lbl, x - (w-10)/2, (y - (h-4)/2) + fm.getAscent());
}
public synchronized void update(Graphics g) {
Dimension d = getSize();
if ((offscreen == null) || (d.width != offscreensize.width) || (d.height != offscreensize.height)) {
offscreen = createImage(d.width, d.height);
offscreensize = d;
if (offgraphics != null) {
offgraphics.dispose();
}
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[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 (stress) {
String lbl = String.valueOf(len);
offgraphics.setColor(stressColor);
offgraphics.drawString(lbl, x1 + (x2-x1)/2, y1 + (y2-y1)/2);
offgraphics.setColor(edgeColor);
}
}
FontMetrics fm = offgraphics.getFontMetrics();
for (int i = 0 ; i < nnodes ; i++) {
paintNode(offgraphics, nodes[i], fm);
}
g.drawImage(offscreen, 0, 0, null);
}
public void mouseClicked(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
numMouseButtonsDown++;
addMouseMotionListener(this);
double bestdist = Double.MAX_VALUE;
int x = e.getX();
int y = e.getY();
for (int i = 0 ; i < nnodes ; i++) {
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();
e.consume();
}
public void mouseReleased(MouseEvent e) {
numMouseButtonsDown--;
removeMouseMotionListener(this);
pick.fixed = pickfixed;
pick.x = e.getX();
pick.y = e.getY();
if (numMouseButtonsDown == 0) {
pick = null;
}
repaint();
e.consume();
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void mouseDragged(MouseEvent e) {
pick.x = e.getX();
pick.y = e.getY();
repaint();
e.consume();
}
public void mouseMoved(MouseEvent e) {
}
public void start() {
relaxer = new Thread(this);
relaxer.start();
}
public void stop() {
relaxer = null;
}
}
public class Graph extends Applet implements ActionListener, ItemListener {
GraphPanel panel;
Panel controlPanel;
Button scramble = new Button("Scramble");
Button shake = new Button("Shake");
Checkbox stress = new Checkbox("Stress");
Checkbox random = new Checkbox("Random");
public void init() {
setLayout(new BorderLayout());
panel = new GraphPanel(this);
add("Center", panel);
controlPanel = new Panel();
add("South", controlPanel);
controlPanel.add(scramble); scramble.addActionListener(this);
controlPanel.add(shake); shake.addActionListener(this);
controlPanel.add(stress); stress.addItemListener(this);
controlPanel.add(random); random.addItemListener(this);
String edges = getParameter("edges");
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);
}
}
Dimension d = getSize();
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;
}
}
public void destroy() {
remove(panel);
remove(controlPanel);
}
public void start() {
panel.start();
}
public void stop() {
panel.stop();
}
public void actionPerformed(ActionEvent e) {
Object src = e.getSource();
if (src == scramble) {
play(getCodeBase(), "audio/computer.au");
Dimension d = getSize();
for (int i = 0 ; i < panel.nnodes ; i++) {
Node n = panel.nodes[i];
if (!n.fixed) {
n.x = 10 + (d.width-20)*Math.random();
n.y = 10 + (d.height-20)*Math.random();
}
}
return;
}
if (src == shake) {
play(getCodeBase(), "audio/gong.au");
Dimension d = getSize();
for (int i = 0 ; i < panel.nnodes ; i++) {
Node n = panel.nodes[i];
if (!n.fixed) {
n.x += 80*Math.random() - 40;
n.y += 80*Math.random() - 40;
}
}
}
}
public void itemStateChanged(ItemEvent e) {
Object src = e.getSource();
boolean on = e.getStateChange() == ItemEvent.SELECTED;
if (src == stress) panel.stress = on;
else if (src == random) panel.random = on;
}
public String getAppletInfo() {
return "Title: GraphLayout \nAuthor: <unknown>";
}
public String[][] getParameterInfo() {
String[][] info = {
{"edges", "delimited string", "A comma-delimited list of all the edges. It takes the form of 'C-N1,C-N2,C-N3,C-NX,N1-N2/M12,N2-N3/M23,N3-NX/M3X,...' where C is the name of center node (see 'center' parameter) and NX is a node attached to the center node. For the edges connecting nodes to each other (and not to the center node) you may (optionally) specify a length MXY separated from the edge name by a forward slash."},
{"center", "string", "The name of the center node."}
};
return info;
}
}
