main_java_com_example_harsh_freechat_FreeChat.java

package com.example.harsh.freechat;

import android.app.Application;
import android.content.Intent;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ServerValue;
import com.google.firebase.database.ValueEventListener;
import com.squareup.picasso.OkHttpDownloader;
import com.squareup.picasso.Picasso;

/**
 * Created by harsh on 27-12-2017.
 */

public class FreeChat extends Application {

    private DatabaseReference mUserDatabase;
    private FirebaseAuth mAuth;


    @Override
    public void onCreate() {
        super.onCreate();

        FirebaseDatabase.getInstance().setPersistenceEnabled(true);

        Picasso.Builder builder=new Picasso.Builder(this);
        builder.downloader(new OkHttpDownloader(this, Integer.MAX_VALUE));
        Picasso built=builder.build();
        built.setIndicatorsEnabled(true);
        built.setLoggingEnabled(true);
        Picasso.setSingletonInstance(built);

       mAuth = FirebaseAuth.getInstance();

            if(mAuth.getCurrentUser()!=null) {
                mUserDatabase = FirebaseDatabase.getInstance()
                        .getReference().child("Users").child(mAuth.getCurrentUser().getUid());

                mUserDatabase.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {

                        if (dataSnapshot != null) {

                            mUserDatabase.child("online").onDisconnect().setValue(ServerValue.TIMESTAMP);



                        }

                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });


            }

    }

}