Still on firebase database, this codes checks for the state of a user in the firebase real tile database state.

ConnectionState.java

  DatabaseReferene connectRef = FirebaseDatabase.getInstance().getReference(".info/connected");
  connectRef.addValueEventListener(new ValueEventListener() {
    @override
    public void onDataCHanged(DataSnapshot dataSnapshot){
      boolean isConnected = dataSnapshot.getValue(Boolean.class);
      if(connected){
        System.out.println("Your are now connected");
      }else{
        System.out.println("Your are disconnected");
      }
    }
    @override
    public void onCanclled(DatabseError error){
      System.out.println("Database error" + error.getMessage);
    }
  });