Android Buttons don't animate the way they're supposed to

I am trying to achieve a screen like this in Android. I have taken the same code from the site & tried it, but it's not animating the buttons. I'm getting by running the following code

My content_main.xml contains the following code: -

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="meetutu.juspay.com.meetutu.MainActivity"
    tools:showIn="@layout/activity_main"
    android:background="#2980B9">


    <ImageView
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:id="@+id/meetutuImageView"
        android:src="@drawable/meetutuimage"
        android:layout_gravity="center"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />

    <RelativeLayout
        android:id="@+id/container"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/meetutuImageView"
        android:layout_centerHorizontal="true">

        <TextView
            android:id="@+id/textView1"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="The joy of meeting an expert teacher"
            android:textAlignment="center"
            android:textColor="#A3E4D7"
            android:layout_centerHorizontal="true"/>
        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="for a craving learner"
            android:textAlignment="center"
            android:textColor="#A3E4D7"
            android:layout_centerHorizontal="true"
            android:layout_below="@+id/textView1"/>

        <Button
            style="@style/Widget.AppCompat.Button.Colored"
            android:id="@+id/loginButton"
            android:layout_width="80dp"
            android:layout_height="wrap_content"
            android:text="LOGIN"
            android:layout_marginTop="44dp"
            android:layout_below="@+id/textView2"
            android:layout_alignLeft="@+id/textView1"
            android:layout_alignStart="@+id/textView1" />

        <Button
            style="@style/Widget.AppCompat.Button.Colored"
            android:id="@+id/signupButton"
            android:layout_width="80dp"
            android:layout_height="wrap_content"
            android:text="SIGN UP"
            android:layout_alignTop="@+id/loginButton"
            android:layout_alignRight="@+id/textView1"
            android:layout_alignEnd="@+id/textView1" />



    </RelativeLayout>


</RelativeLayout>

And my MainActivity.java contains following code:

package meetutu.juspay.com.meetutu;

import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPropertyAnimatorCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.view.ViewGroup;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.*;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private ImageView logoImage;
    private TextView textView1, textView2;
    private ViewGroup container;

    public static final int STARTUP_DELAY = 300;
    public static final int ANIM_ITEM_DURATION = 1000;
    public static final int ITEM_DELAY = 300;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_FULLSCREEN | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LOCKED);


    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {

        if(hasFocus)
            animation();
        super.onWindowFocusChanged(hasFocus);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void animation()
    {
        logoImage = (ImageView) findViewById(R.id.meetutuImageView);
        container = (ViewGroup) findViewById(R.id.container);

        ViewCompat.animate(logoImage)
                .translationY(-200)
                .setStartDelay(STARTUP_DELAY)
                .setDuration(ANIM_ITEM_DURATION)
                .setInterpolator(
                        new DecelerateInterpolator(1.2f)).start();

        for(int i = 0; i < container.getChildCount(); i++)
        {
            View v = container.getChildAt(i);
            ViewPropertyAnimatorCompat viewAnimator;

            if(!(v instanceof Button))
            {
                viewAnimator = ViewCompat.animate(v)
                        .translationY(50).alpha(1)
                        .setStartDelay((ITEM_DELAY * i) + 500)
                        .setDuration(1000);
            }
            else
            {
                viewAnimator = ViewCompat.animate(v)
                        .scaleY(1).scaleX(1)
                        .setStartDelay((ITEM_DELAY * i) + 500)
                        .setDuration(500);
            }

            viewAnimator.setInterpolator(new DecelerateInterpolator()).start();
        }
    }
}

I'm new to Android, so I don't know much about types of animation and how they can be implemented. I want to achieve the animation and smoothness given in the link. Please let me know what else I should add to my code to make it work like that.

Thank you for your time!!