我用java编的多边形裁剪程序，但是有时候能运行，有时候不能运行，大虾帮看下
这是线段裁剪的类，我不知道哪里出问题了……这里我采用了Point intersection(Point p1, Point p2, Point p3, Point p4) 这个函数来进行输入线段和多边形每条线段之间的求交点，当没有交点的时候就返回（0,0），各位大虾快帮我看下阿，想了好几天了，压抑阿
程序代码：class cutall extends JFrame {
JLabel title1, title2, title3, title4;
JTextField t1, t2, t3, t4, t5;
JPanel pane, pan, pa,pb;
int width = getToolkit().getScreenSize().width, minx = -width / 2,
maxx = width / 2;
int height = getToolkit().getScreenSize().height, miny = -height / 2,
maxy = height / 2;
JButton butt;
int rows, rotate[] = new int[1];// rows表示点数
JTable table;
Object a[][];
Object name[] = { "横坐标", "纵坐标" };
cutall() {
pane = new JPanel();
pan = new JPanel();
pa = new JPanel();
pb =new JPanel();
pane.setLayout(new GridLayout(5, 1));
title1 = new JLabel("范围(" + minx + "," + miny
+ ")到(" + maxx + "," + maxy + ")");
title2 = new JLabel(
" 请按照顺时针或者逆时针输入多边形所有点");
title4 = new JLabel("请输入线段的两个端点坐标:");
title3 = new JLabel("输入截线段多边形点的个数，回车确认 ");
butt = new JButton("设置完成");
t1 = new JTextField(10);
t2 = new JTextField(5);
t3 = new JTextField(5);
t4 = new JTextField(5);
t5 = new JTextField(5);
pa.add(title4);
pa.add(t2);
pa.add(t3);
pb.add(title1);
pb.add(t4);
pb.add(t5);
pane.add(pa);
pane.add(pb);
pan.add(title3);
pan.add(t1);
t1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
rows = Integer.parseInt(t1.getText());
a = new Object[rows][2];
for (int i = 0; i < rows; i++) {
for (int j = 0; j < 2; j++)
a[i][j] = 0;
}
table = new JTable(a, name);
table.setRowHeight(20);
getContentPane().removeAll();
add(pane, BorderLayout.NORTH);
add(butt, BorderLayout.SOUTH);
add(new JScrollPane(table), BorderLayout.CENTER);
validate();
}
});
butt.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Point p1 = new Point(Integer.parseInt(t2.getText()), Integer
.parseInt(t3.getText()));
Point p2 = new Point(Integer.parseInt(t4.getText()), Integer
.parseInt(t5.getText()));
new cut(a, p1, p2);
}
});
pane.add(pan);
pane.add(title2);
add(pane, BorderLayout.NORTH);
add(butt, BorderLayout.SOUTH);
add(new JScrollPane(table), BorderLayout.CENTER);
setBounds(440, 250, 400, 300);
setTitle("线段裁剪的基本设置");
setVisible(true);
setResizable(false);
}
}
class cut extends JFrame {
Object a[][];
Point p1, p2;
int i, j, x, y;
int width = getToolkit().getScreenSize().width, minx = -width / 2,
maxx = width / 2;
int height = getToolkit().getScreenSize().height, miny = -height / 2,
maxy = height / 2;
public cut(Object a[][], Point p1, Point p2) {
this.p1 = p1;
this.p2 = p2;
this.a = a;
add(new cutpolygo());
setTitle("线段的裁剪设置");
setLocation(0, 0);
setSize(width, height);
setVisible(true);
setVisible(true);
setVisible(true);
setResizable(false);
}
class cutpolygo extends JPanel {
public void paintComponent(Graphics g) {
int j = 0, c, d, len[] = new int[20];
Point pp[] = new Point[20];
Point p3, p4, p0 = new Point(0, 0), p5 = new Point(0, 0);
Graphics2D t = (Graphics2D) g;
Polygon p = new Polygon();
p1.x=p1.x+maxx;
p1.y=maxy-p1.y;
p2.x=p2.x+maxx;
p2.y=maxy-p2.y;
for (int i = 0; i < a.length; i++) {
x = Integer.parseInt(a[i][0].toString()) + maxx;
y = -Integer.parseInt(a[i][1].toString()) + maxy;
p.addPoint(x, y);
p3 = new Point(x, y);
c = Integer.parseInt(a[(i + 1) % a.length][0].toString())+ maxx;
d = -Integer.parseInt(a[(i + 1) % a.length][1].toString())+ maxy;
p4 = new Point(c, d);
pp[j] = intersection(p1, p2, p3, p4);
if (pp[j] != p0)
j++;
}
t.drawPolygon(p);
t.setColor(Color.red);
t.drawLine(p1.x, p1.y, p2.x, p2.y);
for (int s = 0; s < j; s++)
len[s] = (p1.x - pp[s].x) * (p1.x - pp[s].x) + (p1.y - pp[s].y)
* (p1.y - pp[s].y);
for (int n = 0; n < j - 1; n++) {
for (int m = 0; m < j - n - 1; m++) {
if (len[m] > len[m + 1]) {
p5 = pp[m];
pp[m] = pp[m + 1];
pp[m + 1] = p5;
}
}
}
for (i = 0; i < j; i = i + 2) {
t.setColor(Color.green);
t.drawLine(p1.x, p1.y, pp[i].x, pp[i].y);
}
t.setColor(Color.green);
t.drawLine(p2.x, p2.y, pp[i-1].x, pp[i-1].y);
}
}
Point intersection(Point p1, Point p2, Point p3, Point p4) {
Point p = new Point(0, 0);
float x1 = p1.x, x2 = p2.x, x3 = p3.x, x4 = p4.x;
float y1 = p1.y, y2 = p2.y, y3 = p3.y, y4 = p4.y;
float d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
if (d == 0)
return p;
float pre = (x1 * y2 - y1 * x2), post = (x3 * y4 - y3 * x4);
float x = (pre * (x3 - x4) - (x1 - x2) * post) / d;
float y = (pre * (y3 - y4) - (y1 - y2) * post) / d;
if (x < Math.min(x1, x2) || x > Math.max(x1, x2)
|| x < Math.min(x3, x4) || x > Math.max(x3, x4))
return p;
if (y < Math.min(y1, y2) || y > Math.max(y1, y2)
|| y < Math.min(y3, y4) || y > Math.max(y3, y4))
return p;
Point ret = new Point();
ret.x = (int) x;
ret.y = (int) y;
return ret;
}
}
