I have a Login Activity which stores credentials in its own SharedPreferences; then I added two getters for reading them, something like

public String getUsername() {
  return getPreferences(MODE_PRIVATE).getString("#username", null);
}

but this throws a NPE when I call it like this

String mUser = (new Login()).getUsername();

It seems that the Activity cannot read its preferences after a simple contructor call, as if it were in some uncompleted state. I read lots of related topics, but wasn't able to find a solution. Basically, I need to share these credentials among activities in my application