如何在JPanel中的mouselistener类中注册两个点？

Question

This one's been baffling me, I've a board and I want to be able to move a checker piece from one place to another.. I've set the frame to a grid layout, and each grid cell has a new JPanel that implements mouseListener.. how can I register the points start and end so that I can move the checker piece? I'm not able to save the point I'm at to a temp as it changes whenever I click another point..

Here's the code:

public class Tiles extends JPanel implements MouseListener {

Color c2, cc, tmp;
boolean isWhite, hasChecker, isHighlighted;
int i, j;
ArrayList<Point> al = new ArrayList<Point>();
ArrayList<Point> TempArray = new ArrayList<Point>();
Point start;
Point temp;

public Tiles(Color c, Point s){

     this.setSize(75, 75);
     this.setLayout(null);
     this.addMouseListener(this);
     this.c2 = c;
     tmp = c2;
     this.start = s;

  }

public void setWhite(boolean isWhite){
    this.isWhite = isWhite;
}

public void hasChecker(boolean hasChecker){
    this.hasChecker = hasChecker;
}

public void paintComponent(Graphics g){
    Graphics2D g2 = (Graphics2D)g;
    super.paintComponent(g2);
    //if(isClicked == true)
    //  highlightPossibleMoves(start);
    drawTile(g2);
    if(hasChecker == true)
        addCheckers(g2);



}

public void drawTile(Graphics2D g2){

    g2.setColor(c2);

    g2.fillRect(3, 3, 75, 75);

}

public void addCheckers(Graphics2D g2){
    if(isWhite == true){
        g2.setColor(Color.white);
    }
    else{
        g2.setColor(Color.black);
    }
    Ellipse2D.Double circle = new Ellipse2D.Double(13, 11, 50, 50);
    g2.fill(circle);
}

public boolean highlightPossibleMoves(Point start){
    al = LOA.b.getPossibleMoves(start);
    if(!al.isEmpty()){
        for(int i = 0; i<al.size(); i++){
            LOA.Jboard[al.get(i).getY()][al.get(i).getX()].c2 = Color.green;
            LOA.Jboard[al.get(i).getY()][al.get(i).getX()].repaint();
        }
        return true;
    }
    return false;
}

public Point getThisPoint(){
    return this.start;
}

public boolean isPossible(Point p){
    if (TempArray.contains(p)){
        System.out.println("contains");
        return true;
    }
    return false;
}

    @Override
public void mouseClicked(MouseEvent e) {

}

@Override
public void mouseEntered(MouseEvent arg0) {

}

@Override
public void mouseExited(MouseEvent arg0) {

}

@Override
public void mousePressed(MouseEvent e) {

}

@Override
public void mouseReleased(MouseEvent e) {
        if(isHighlighted = true){
            LOA.initBoard();
        }
        if(highlightPossibleMoves(getThisPoint()) == true){
            this.isHighlighted = true;
        }           
        if(isPossible(getThisPoint()))
            LOA.move(this.temp, getThisPoint());
        else{
            System.out.println("x =" + this.start.getX() + "y =" + this.start.getY());
            this.temp = new Point(getThisPoint().getX(), getThisPoint().getY());
        }
        this.repaint();
        this.validate();                        
}
}

Answer 1

I can give you business logic for the same:

• Create board with grid layout
• Instead of JPanels, I would reckon JButtons (set the JButton's name a1, a2, a3.. based on their location)
• Once a user click a button, change the selected button color to green maybe (you can easily store the selected button name and know what button has been selected.. you can also update the number of count to one in order to keep track that piece has not yet moved)
• Thenceforth, when user click another button ie user select another valid grid.. you can make the move on the board

This way you don't have to worry about saving a point but saving a selected component

Answer 2

You need to have somewhere in your mousePressed(...) method,

if (start != null) {  // second press
  // second point pressed
  //.... do some junk

  start = null; then set start to null

} else { // first press
   start = ...;
}