我想在我的应用程序中添加一个功能,允许用户通过在起始位置单击鼠标并在结束位置释放它来绘制直线.当鼠标移动直到最终释放时,线应该移动;类似于使用Microsoft Paint应用程序绘制线条的方式.

如何实现这一点,以便线条在移动时重新绘制,而不重新绘制可能已在该矩形区域中绘制的其他内容？

解决方法:

试试这个……当鼠标移动(拖动)时,在屏幕上画一条红线.

public static void main(String args[]) throws Exception {
    JFrame f = new JFrame("Draw a Red Line");
    f.setSize(300, 300);
    f.setLocation(300, 300);
    f.setResizable(false);
    JPanel p = new JPanel() {
        Point pointStart = null;
        Point pointEnd   = null;
        {
            addMouseListener(new MouseAdapter() {
                public void mousePressed(MouseEvent e) {
                    pointStart = e.getPoint();
                }

                public void mouseReleased(MouseEvent e) {
                    pointStart = null;
                }
            });
            addMouseMotionListener(new MouseMotionAdapter() {
                public void mouseMoved(MouseEvent e) {
                    pointEnd = e.getPoint();
                }

                public void mouseDragged(MouseEvent e) {
                    pointEnd = e.getPoint();
                    repaint();
                }
            });
        }
        public void paint(Graphics g) {
            super.paint(g);
            if (pointStart != null) {
                g.setColor(Color.RED);
                g.drawLine(pointStart.x, pointStart.y, pointEnd.x, pointEnd.y);
            }
        }
    };
    f.add(p);
    f.setVisible(true); 
}