打开一个线文件和保存改变过的线文件，编辑线的属性和参数（调用mapgis函数）； 用橡皮筋的形式输入线，可以用F3撤销F4恢复-Open a line file and save the changed line files, edit the line attributes and parameters (call mapgis function) the form of input line with a rubber band, you can use F3 F4 withdrawa