编写一个程序，实现一串文字在屏幕正中沿300×300的矩形边界移动 //谁有空自己改下算法。。。。个人认为这个算法太死。。。只能在个人的屏幕 //中间的位置画图形-Write a program to achieve a string of text in the middle of the screen 300 × 300 rectangle along the border mobile// who is available to change the algorithm itsel