For Android 3.x and before, you can bring up a hidden UI called com.android.settings.ProxySelector. It is set in Settings.Secure.HTTP_PROXY and used by Mobile network (WiFi network does not always work). However for ICS, I can still bring up this hidden UI, but it does not seem to set proxy anymore. When I click "Done", then I check Settings.Secure.HTTP_PROXY or system property http.proxyHost, neither is set.
So is there a way in ICS that would allow me to set global proxy much like what I can do before with the com.android.settings.ProxySelector UI? Thanks!
Unfortunately the hidden activity "com.android.settings.ProxySelector" is not designed for setting the proxy for Wi-Fi networks. In fact you can set a global proxy using this activity but for standard applications you won't see a change.
For example the default browser use this setting only for MOBILE networks and completely ignore it for Wi-Fi networks.
Of course you can read the settings in your personal app using this library, but you can't expect that other applications will do the same :(
Please let me know if everything is clear. Anyway I'm trying to cover the problem here, so you can find more resources on this topic.
if the device is rooted. you can edit the Iptable
来源：https://stackoverflow.com/questions/10559370/how-to-set-system-wide-proxy-in-ics