android studio运行时提示All packages are not available for download! the following package are not availa

android studio运行时提示

All packages are not available for download!
the following package are not available;

 -Package id system-images;android-19;default;armeabi-v7a

原因：

我解决办法，之前为了翻墙修改了host文件，里面就有google的站点，域名对应着ip地址，过了一段时间肯定就变了，所以下载不了SDK。把host文件里面内容删除就是了。用switchhost切换到新host即可

http://bbs.youkuaiyun.com/topics/392002942