消除SDK更新时，有可能会出现这样的错误：
Download interrupted: hostname in certificate didn‘t match: <dl-ssl.google.com> != <www.google.com>
Download interrupted: Connection to https://dl-ssl.google.com refused
Done. Nothing was installed.
解决办法是：将https://修改为http://
修改方法是：如下图，在Android SDK Manager->Tools-Options...选项界面，
将“Force https://… sources to be fetched using http://…”勾选！
如果还有错，可以在文件（C:\Windows\System32\drivers\etc\hosts）中，添加如下几行：
203.208.46.146 www.google.com
203.208.46.146 dl.google.com
203.208.46.146 dl-ssl.google.com