Java Android Chat Application

public class Chat extends AppCompatActivity
{
    LinearLayout layout;
    RelativeLayout layout_2;
    ImageView sendButton;
    EditText messageArea;
    ScrollView scrollView;
    Firebase reference1, reference2;
    boolean timerProcessing = false;
    boolean timerStarts = false;
    String date = "";
    String message;
    String userName;
    int value = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);

        layout = (LinearLayout) findViewById(R.id.layout1);
        layout_2 = (RelativeLayout)findViewById(R.id.layout2);
        sendButton = (ImageView)findViewById(R.id.sendButton);
        messageArea = (EditText)findViewById(R.id.messageArea);
        scrollView = (ScrollView)findViewById(R.id.scrollView);

        Firebase.setAndroidContext(this);
        reference1 = new Firebase("https://zipa1x.firebaseio.com/messages/" + UserDetails.username + "_" + UserDetails.chatWith);
        reference2 = new Firebase("https://zipa1x.firebaseio.com/messages/" + UserDetails.chatWith + "_" + UserDetails.username);

        sendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String messageText = messageArea.getText().toString();

                if(!messageText.equals(""))
                {
                    Map<String, String> map = new HashMap<String, String>();
                    map.put("message", messageText);
                    map.put("user", UserDetails.username);

                    reference1.push().setValue(map);
                    reference2.push().setValue(map);
                    messageArea.setText("");
                }
            }
        });

        reference1.addChildEventListener(new ChildEventListener()
        {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s)
            {
                Map map = (Map) dataSnapshot.getValue();

                message = map.get("message").toString();
                userName = map.get("user").toString();


                String lastMessage = String.valueOf(map.values().toArray()[map.size() - 2]);
                Log.e("LAST MESSAGE", lastMessage);

                if (userName.equals(UserDetails.username))
                {
                    addMessageBox(message, 1);
                }
                else
                {
                    addMessageBox(message, 2);
                    if(message == lastMessage)
                    {
                        sendNotification(lastMessage);
                    }
                }
            }

            @Override
            public void onChildChanged(final DataSnapshot dataSnapshot, String s)
            {

            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(FirebaseError firebaseError) {

            }
        });

        scrollView.post(new Runnable() {
            @Override
            public void run() {
                scrollView.fullScroll(View.FOCUS_DOWN);
            }
        });
    }
    TextView textView,textView2;
    public void addMessageBox(String message, int type)
    {
        DateFormat df = new SimpleDateFormat("h:mm a");
        date = df.format(Calendar.getInstance().getTime());

        TextView textView1 = new TextView(Chat.this);
        textView1.setText(date);
        textView1.setTextSize(10);

        textView = new TextView(Chat.this);
        textView.setText(message);

        LinearLayout.LayoutParams lp2 = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        lp2.weight = 1.0f;

        if(type == 1) {
            lp2.gravity = Gravity.RIGHT;
            textView.setBackgroundResource(R.drawable.left_bubble);
        }
        else{
            lp2.gravity = Gravity.LEFT;
            textView.setBackgroundResource(R.drawable.right_bubble);
        }
        textView.setLayoutParams(lp2);
        layout.addView(textView);

        textView1.setLayoutParams(lp2);
        layout.addView(textView1);

        scrollView.post(new Runnable() {
            @Override
            public void run() {
                scrollView.fullScroll(View.FOCUS_DOWN);
            }
        });
    }

    private void sendNotification(String message)
    {
        Intent intent = new Intent(this,Chat.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent,PendingIntent.FLAG_ONE_SHOT);

        Uri notificationSound = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

        NotificationManager notificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);

        NotificationCompat.Builder builder = (NotificationCompat.Builder) new NotificationCompat.Builder(this)
                .setVisibility(Notification.VISIBILITY_PUBLIC)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle(userName)
                .setContentText(message)
                .setSound(notificationSound)
                .setContentIntent(pendingIntent);

        NotificationManager mNotificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        mNotificationManager.notify(0, builder.build());
    }