Circular Reveal Animation

Google Maven Repository:

maven {
            url "https://maven.google.com"
        }

Design Support Library: 

developer.android.com/topic/libraries/support-library/packages#design

<?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"
    tools:context="com.example.application.exampleproject.MainActivity">

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentBottom="true"
        android:layout_marginEnd="26dp"
        android:layout_marginBottom="32dp"
        android:src="@mipmap/ic_launcher"
        app:fabSize="normal" />

    <Button
        android:id="@+id/button_reveal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@id/button_hide"
        android:layout_alignBottom="@id/button_hide"
        android:layout_marginEnd="35dp"
        android:layout_toStartOf="@id/button_hide"
        android:text="reveal" />

    <Button
        android:id="@+id/button_hide"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@id/fab"
        android:layout_marginEnd="35dp"
        android:layout_toStartOf="@id/fab"
        android:text="hide" />

</RelativeLayout>

package com.example.application.exampleproject;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewAnimationUtils;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private Button buttonReveal;
    private Button buttonHide;

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

        buttonReveal = findViewById(R.id.button_reveal);
        buttonHide = findViewById(R.id.button_hide);

        buttonReveal.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                revealFAB();
            }
        });

        buttonHide.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                hideFAB();
            }
        });
    }

    private void revealFAB() {
        View view = findViewById(R.id.fab);

        int cx = view.getWidth() / 2;
        int cy = view.getHeight() / 2;

        float finalRadius = (float) Math.hypot(cx, cy);

        Animator anim = ViewAnimationUtils.createCircularReveal(view, cx, cy, 0, finalRadius);
        view.setVisibility(View.VISIBLE);

        anim.start();
    }

    private void hideFAB() {
        final View view = findViewById(R.id.fab);

        int cx = view.getWidth() / 2;
        int cy = view.getHeight() / 2;

        float initialRadius = (float) Math.hypot(cx, cy);

        Animator anim = ViewAnimationUtils.createCircularReveal(view, cx, cy, initialRadius, 0);

        anim.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationEnd(animation);
                view.setVisibility(View.INVISIBLE);
            }
        });

        anim.start();
    }
}