Check if there is at least one user authenticated on Twitter. Note: this can work for any other app using the AccountManager for the authentication if you pass the right "type". e.g. for vine: "co.vine.android.auth" e.g. for linkedin: "com.linkedin.android"

AccountChecker.java

public boolean isTwitterSignedIn(){
  AccountManager manager = AccountManager.get(this);
  Account[] account = manager.getAccountsByType("com.twitter.android.auth.login");
  if (account.length > 0) {
    Log.d("MainActivity", "Authenticated on twitter!");
    return true;
  } else {
    return false;
  }
}