If you cannot start Android Studio or cannot build and run Android apps, the reason maybe that Android SDK or related resources cannot be downloaded correctly.
If so, you may fix this problem by setting proxy information on Android Studio.
1. Install shadowsocks gui client, register account, and fill server information. (shadowsocks listen localhost on port 1080 for socks proxy supporting)
2. Install privoxy, add one line like following to its configuration file (/usr/local/etc/privoxy/config) for converting http proxy to socks proxy, and starts services (privoxy listen localhost on port 8118 by default)
forward-socks5 / 127.0.0.1:1080 .
3. Open Android Studio Preferences by Command+,:
Change HTTP Proxy setting: set Host name to 127.0.0.1, set Port number to 8118.
4. Select "Android SDK", click "Launch Standalone SDK Manager":
5. Open Android SDK Manager Preferences by Command+,:
Set HTTP Proxy Server to 127.0.0.1, HTTP Proxy Port to 8118.
Restart Android Stduio, maybe it works now.