First, setup VPNUAuthorizer instance.

VPNUAuthorizer vpnuAuthorizer = VPNUFacade.getInstance().getVpnuAuthorizer();

Then, you can log in using user's credentials:

String login = "login@some.domain";
String password = "password";
try {
    VPNUAccountUserInfo userInfo = vpnuAuthorizer.authorizeWithLogin(login, password);
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "authorization failed with error code: " + exception.getResponse().getResponseCode()
             + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

If authorization is successful, the VPNUTransport instance is managing the newly created session and reconnects automatically when this session is expired. Retrieved authorization info is saved into VPNUAccountUserInfo

First, setup VPNUAuthorizer instance.

VPNUAuthorizer vpnuAuthorizer = VPNUFacade.getInstance().getVpnuAuthorizer();

Then, you can register new user using user's credentials. VPNUAuthorizer#registerWithLogin will automatically log in a newly created user.

String login = "login@some.domain";
String password = "password";
try {
    userInfo = VPNUFacade.getInstance().authorizer.registerWithLogin(email, password, false)
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "registration failed with error code: " + exception.getResponse().getResponseCode()
             + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

You have to be logged in in order to perform this operation successfully. See two previous answers.

boolean signOutSuccessful = false;
try {
  signOutSuccessful = vpnuAuthorizer.logOut();
  //or /* /. VPNUFacade.getInstance().vpnuConfigurator.onLogout() */
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "Log out failed with error code: " + exception.getResponse().getResponseCode()
                + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

also, you need to stop vpn connection and delete all user data

Assuming you are logged in:

try {
    VPNUAccountManager vpnuAccountManager = VPNUFacade.getInstance().getVpnuAccountManager();
    VPNUAccountStatus accountStatus = vpnuAccountManager.getStatus();
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "Status loading failed with error code: " + exception.getResponse().getResponseCode()
        + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

try {
    VPNUServersManager vpnuServersManager = VPNUFacade.getInstance().getVpnuServersManager();
    List<VPNUServer>  servers = vpnuServersManager.getServers();
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "Servers list loading failed with error code: " + exception.getResponse().getResponseCode()
        + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

First, setup VPNUConfigurator instance.

VPNUConfigurator vpnuConfigurator = VPNUFacade.getInstance().getVpnuConfigurator();

Then you can setup the selected server item (see previous question on how to retrieve it). You can choose protocol settings for VPN connection by passing VPNUProtoConfig entity as a parameter to the VPNUConfigurator#setup method.

try {
    VPNUConfigurator vpnuConfigurator = VPNUFacade.getInstance().getVpnuConfigurator();
    vpnuConfigurator.prepare();
    vpnuConfigurator.setup(server, new VPNUProtoConfig(false, Transport.TCP));
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "set up of Vpn failed with error code: " + exception.getResponse().getResponseCode()
    + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

You then can try to connect to a selected server. In order to obtain the connection status, use the OpenVpnStatusChangedListener by passing an instance to the VPNUConfigurator#addOnStatusChangedListener method of VPNUConfigurator. This method blocks a calling thread.

try {
    VPNUConfigurator vpnuConfigurator = VPNUFacade.getInstance().getVpnuConfigurator();
    vpnuConfigurator.startVpn();
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "start Vpn failed with error code: " + exception.getResponse().getResponseCode()
    + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}

This exception thrown when User not granted VPN permission for app. If permission dialog is never shown to user, You probably need to check BaseDialogActivity implimentation and declaration in manifest file of Your app.

In order to properly display VPN Unlimited SDK dialogs you need to create a class that extends KSDefaultDialogActivityand declare it in the Manifest as an activity with the Intent filter for action: keepsolid.com.androidvpnunlimitedsdk.dialogs.DialogActivity.LAUNCH_INTENT_ACTION.

public class BaseDialogActivity extends KSDefaultDialogActivity {

    @Override
    protected void onCreate(Bundle bundle) {
        super.onCreate(bundle);
    }
}

<activity
    android:name=".BaseDialogActivity"
    android:excludeFromRecents="true">
        <intent-filter>
            <action android:name="your.application.package.name.DialogActivity.LAUNCH_INTENT_ACTION" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
</activity>

Note that you need to replace your.application.package.name with the real package name of your application.

Actually, you cannot disable it. The notification is necessary to prevent the Service got killed by the Android OS task manager.

try {
    VPNUConfigurator vpnuConfigurator = VPNUFacade.getInstance().getVpnuConfigurator();
    vpnuConfigurator.stopVpn();
} catch (VPNUException exception) {
    Log.v(LOG_TAG, "Stop Vpn failed with error code: " + exception.getResponse().getResponseCode()
    + ", and error msg " + exception.getResponse().getResponseMessage());
    exception.printStackTrace();
}