I know of enabling or disabling wifi:
WifiManager wifiManager = (WifiManager)this.context.getSystemService(Context.WIFI_SERVICE);
wifiManager.setWifiEnabled(status);
where status may be true
or false
as per requirement.
Edit:
You also need the following permissions in your manifest file:
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>