这是一个简单的画图程序，可以画三种图：长方形，椭圆，直线。实现了拖动图形，交换位置，删除图形等功能。运用了MVC模式，希望对程序员们可以有些帮助。-This is a simple program of drawing shapes. It can draw three shapes: rectangle,oval and line.It has the dragging function,switching fucntion and deleting function. It uses