1、 计算SW公式: 参考:https://blog.csdn.net/tung214/article/details/46054233
sw-xxxx-dp的计算公式是 sw *160/dpi
2、 屏幕适配文章参考:
https://blog.csdn.net/shanshui911587154/article/details/88395425
https://blog.csdn.net/WHB20081815/article/details/76937801
https://www.cnblogs.com/soaringEveryday/p/4835839.html
https://blog.csdn.net/qq_20330595/article/details/77933958
生成swwidth值 : Math.round(num * 300 / 400)