如果还是不OK，删除Platform和Plugins两个目录，重新添加下平台试试。
参考链接：https://stackoverflow.com/questions/31310182/error-could-not-find-gradle-wrapper-within-android-sdk-might-need-to-update-yo
http://blog.csdn.net/qq_37988919/article/details/70226741
https://stackoverflow.com/questions/42668185/could-not-find-gradle-wrapper-within-android-sdk-might-need-to-update-your-andr
http://blog.csdn.net/gufeilong/article/details/68488828
http://www.cnblogs.com/weiweictgu/p/6752599.html