1 利用基本MVC模式实现下图所示的应用程序，程序主要功能如下：
（1）当用户在图形化用户界面输入一个圆的半径时，程序将显示该圆的周长与面积，并画出该圆（如图中右面所示）；
（2）当用户在图形化用户界面上拖动表示圆半径的标尺时，自动显示圆的半径、周长和面积；并在图形界面上画出图形；
（3）假设程序需再扩充一项功能：要求在程序界面上显示该半径的球体的表面积，试分析如何实现这一功能，并实现该功能。
(1 using the basic MVC model to achieve the following figure shows the application, the program main functions are as follows:
 
(1) When the user enters a radius of the circle in the graphical user interface, the program will display the circumference and area of the circle and draw the circle (as shown in the figure)
(2) When the user drags a ruler representing the radius of the circle on the graphical user interface, the radius, circumference and area of the circle are automatically displayed　and the graph is drawn on the graphical interface
(3) Assume that the program needs to be extended to a function that requires the surface area of the sphere to be displayed on the program interface, try to figure out how to implement this function, and implement this function.)