Android VPN connector demo

I need to make an Android VPN client for our VPN users to replace the Android system settings UI, with on click to connect to our VPN server. I need an expert provide the technique that how to connect VPN server in an Android app. The following is the specification: 1. Protocal: PPTP?Android version: 4.x 2. just the function, no need to design pretty UI 3. There are 3 input fields on the UI: server IP addr, username and password; 1 checkbox "encrypt"; 1 button "connect". Once user click the button, all his internet access will go through VPN. no need root. 4. There is a route table within the app including the IP address range for Chinese mainland, so that the VPN tunnel can be bybassed when user access Chinese website 5. I need the complete and readable source code of java for it. I will provide the developer with the VPN server IP and test account.