鼠标按下，画出图形的主要部分

来源：互联网发布：dmg mac u盘知乎编辑：程序博客网时间：2024/06/08 06:20

class MouseComponent extends JComponent {
public MouseComponent() {
  squares = new ArrayList<Rectangle2D>();
  current = null;

  this.addMouseListener(new MouseHandler());
  this.addMouseMotionListener(new MouseMotionHandler());
}

@Override
public void paintComponent(Graphics g) {
  Graphics2D g2 = (Graphics2D) g;

  for(Rectangle2D r : squares) {
   g2.draw(r);
  }
}

/**
* 点击的这个点，是否在某个图形内
* @param p 点击的点
* @return 在图形内，返回这个图形。不在图形内，返回null。
*/
public Rectangle2D find(Point2D p) {
  for(Rectangle2D r : squares) {
   if(r.contains(p)) {
    return r;
   }
  }

  return null;
}

/**
* 将这个点的图形添加到list中，并重新绘制图形
* @param p 要添加的点
*/
public void add(Point2D p) {
  double x = p.getX();
  double y = p.getY();

  current = new Rectangle2D.Double(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH, SIDELENGTH);
  squares.add(current);
  repaint();
}

/**
* 从list中移除图形
* @param s 要移除的图形
*/
public void remove(Rectangle2D s) {
  if(s == null) {
   return;
  }
  //将当前的置为null
  if(s == current) {
   current = null;
  }

  squares.remove(s);
  repaint();
}

private static final int SIDELENGTH = 10;
private Rectangle2D current;
private ArrayList<Rectangle2D> squares;

}