设计一个窗口，有导入、平均值、增加、查找、保存五个功能，有文件、结果、学生、成绩五个文本框，能实现对文档的导入，并能实现向文档中添加语句，还可以计算平均值和按目标查找数据。-Design a window with import, the average increase, find, save five functions, documented as a result, students, grades five text boxes, to achieve the import of th