Well, let's say I wanted to do a puzzle.

Question

It's not exactly what I'm trying to do, but I think a puzzle is a good way of describing the problem at hand. I want to lay out one new piece every time I choose the "new piece" option from a menu. Obviously the pieces I've already laid down should not move or disappear(until I say so at least). So you might say I got this incremental thing going on, with new images continously being added to my JPanel. I've tried this, and
it did not turn out well:
So, everytime repaint() is called this happens:
public void paintComponent(Graphics g)
super.paintComponent(g);
index=1;//
u =0;//the matrix placeholder for the x-coordinate;
v =0 ;//the matrix placeholder for the y-coordinate;
//x and y are updated elsewhere, and put in their respective slots
if(img[index] = null)
Rectangle rec = this.getBounds();
g.fillRect(0,0,(int)rec.getWidth(),(int)rec.getHeight());
for(temp=0;temp<index;temp++)//draw all previous images along with this
u++;
v++;
g.drawImage(img[index],imgCoordinates[u][v],this);
index++;//the next time a image loads, it's in the next slot
temp = 0;//zero's out so it's prepared for next redraw
//}//end if
}//end paintComponent
I'm sure the solution is quite within reach, but I just dont know where to start. The most important question is probably: Do I need to redraw the entire screen everytime I add another picture, or is it possible to just
draw the new one, leaving the other parts of the screen alone? Must I get involved with threads?
What about seralization? Please expand my knowledge of such things.
Best regards from frosty norway.

Answer 1

Sorry bout the bad coding above. Absolutely terrible. Have not used array's
for a while see. Here's what I actually meant to write:)
   //let's say I have 20 pieces
    private Image[] img= new Image[20];
    private int[] coor = new int[20];
    int x,y //actual x,y screen coordinates
    int u=0;//x coordinates will be stored at only even numbers;
    int v=1; //y coordinates will be stored at only odd numbers;
public void mousePressed(MouseEvent e
     index++;// p.s I have a default image in img[0]
      u =u+2;//2,4,6...
      v  =v+2;//3,5,7...
      img[index] = source.getImage();//get the image
      coor[u]     = x;//store x
      coor[v]     =  y;//store y
}//end mousePressed
public void paintComponent(Graphics g)
    super.paintComponent(g);
    if(img[index] != null)
      Rectangle rec = this.getBounds();
      g.fillRect(0,0,(int)rec.getWidth(),(int)rec.getHeight());
      for(int i=0;i<index;i++)
        g.drawImage(img,coor[i],coor[i+1],this);
}//end for
}//end if
}//end paintComponent
So what's wrong with this picture? As you see, the pieces are Images so they count as objects all right, but they hardly count as components(Image is not a subclass of Component).
Maybe it's time I got involved with Graphics 2D? And I have been wondering about this validate method
also. What's that about?
And last but not least what's a null-layout panel?
Thanks for cooperating.
Tore.