Android PPTP VPN connector

I need to make an Android VPN client for our VPN users to replace the Android system settings UI, with one click to connect to our VPN server. I need an expert to implement PPTP protocal on Android 4.x with VpnService API of Android SDK. 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. I need the complete and readable source code of java for it. To bid on the project , you need to prove you do have the skill needed for this project, especially the knowledge of PPTP protocal.