ArrayList -> Polygon?
Hi,
in my game the user clicks with the mouse to position the player; each position is stored in an ArrayList:private List <Ellipse2D>playerAllCoordinates =new ArrayList<Ellipse2D>();
Now I need these coordinates for collision detection; for this I am using the polygon class.
Is it possible to construct a polygon using the x and y coordinates stored in this ArrayList (or a similar ArrayList so that I can paint a polygon using the stored coordinates?)?
[560 byte] By [
SFLa] at [2007-11-27 2:57:29]
# 1
From the API doco
Polygon
public Polygon(int[] xpoints,
int[] ypoints,
int npoints)
Constructs and initializes a Polygon from the specified parameters.
Parameters:
xpoints - an array of x coordinates
ypoints - an array of y coordinates
npoints - the total number of points in the Polygon
Throws:
So the answer is ... if you have the correct number of [x,y] coordinates in your ArrayList, then yes you can do it.
# 2
Is one array sufficient or do I need 2 arrays, the second storing the vertices? How could I store the vertices?
SFLa at 2007-7-12 3:36:02 >
# 3
The Polygon can be any number of vertices ... it depends on the number of [x,y] coordinates you have - that's what the third 'int' parameter specifies. So if each ArrayList contains six pairs of [x,y] coordinates, than each ArrayList will represent one Polygon. Or am I missing
# 4
Ok.... I am really uncertain in this topic... I am asking about this ArrayList because I need to remove points from a polygon... that's why I thought I can store the coordinates in an ArrayList, adding and removing coordinates to / from this ArrayList and finally drawing the polygon. I noticed that the polygon class don't have a "removePoint" method :/
SFLa at 2007-7-12 3:36:03 >
# 5
This is the first time that I read that you want the coordinates back out. I have not tried it, but perhaps the getPathIterator will do what you want.
# 6
I now tried something like this:
private List playerPolygonCoordinates = new ArrayList();
private Polygon playerPolygon = new Polygon();
private Point2D playerCurrentPosition;
(...)
public void mouseClicked(MouseEvent evt) {
playerCurrentPosition = new Point2D.Double(evt.getX(), evt.getY());
playerPolygonCoordinates.add(playerCurrentPosition);
(...)
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
for(int i=1 ; i < playerPolygonCoordinates.size(); i++) {
playerPolygon = (Polygon) playerPolygonCoordinates.get(i);
g2.draw(playerPolygon);
}
(...)
...with every mouse click I am adding points to the array list and can then draw the polygon... however, this doesn't work... to remove a coordinate from the polygon I then would just remove one coordinate pair from the array list and redraw the whole polygon.. hmmm....
SFLa at 2007-7-12 3:36:03 >
# 7
private Point playerCurrentPosition;
/* ... */
public void mouseClicked(MouseEvent evt) {
playerCurrentPosition = new Point(evt.getX(), evt.getY());
playerPolygonCoordinates.add(playerCurrentPosition);
/* ... */
protected void paintComponent(Graphics g) {
super.paintComponent(g);
int size = playerPolygonCoordinates.size();
int[] x = new int[size];
int[] y = new int[size];
for (int i=1 ; i < size; i++) {
Point point = ((Point) playerPolygonCoordinates.get(i));
x[i] = point.getX();
y[i] = point.getY();
}
g.drawPolygon(x,y,size);
}
Message was edited by:
abillconsl
# 8
Thanks, it works :)
How could I now construct a polygon from the playerPolygonCoordinates list (something like playerPolygon = (Polygon) playerPolygonCoordinates.get(i); // not working :(
) so that I can later define an area like playerArea = new Area(playerPolygon);
?
One more question.. I think it's not possible: could I draw the polygon without drawing the last line segment between first and final pairs of coordinates?
Message was edited by:
SFL
SFLa at 2007-7-12 3:36:03 >
# 9
You are welcome, but that last post of your confused me.
First you said it's working and then immediately precede to say it does not work and display a line of code that I had hoped you would have displaced/replaced with the code I gave you.
As to the other questions regarding not closing the polygon ... look at drawPolyline instead - this will do what I think you want.
# 10
no, everything is fine... I played with various approaches and thought that I can, using your code, manage to put all coordinates into a Polygon variable... I already abandoned it... newbie thoughts :)Thanks!
SFLa at 2007-7-12 3:36:03 >
# 11
Ok ... well ... you're welcome ... I suppose ...
# 12
Solved, using GeneralPath instead.
SFLa at 2007-7-12 3:36:03 >
