QCompleter用法参考如下链接:
http://blog.youkuaiyun.com/taiyang1987912/article/details/35287023
http://blog.youkuaiyun.com/hai200501019/article/details/8455808
http://blog.youkuaiyun.com/taiyang1987912/article/details/50541458
其他实现方法:
http://www.cppblog.com/biao/archive/2009/10/31/99873.html
http://blog.youkuaiyun.com/starcloud_zxt/article/details/5186489