react-native-router-flux disabling android back button from going back to login screen

Using react-native-router-flux, after user was success login, I would like to disable the back button from going back to the login screen.But I can not seem to find a way of getting the current "Scene" or "Stack" and then make some login as:

backAndroidHandler={() => {                        if (currentScene === afterLoginScreeen) {                         return true;                           }                    }}

Did any one manage to deal with this issue?