In this tutorial you will learn how to implement the circular reveal using the Animator class.

What is Animator?

It is the superclass for classes which provide basic support for animations which can be started, ended, and have AnimatorListeners added to them.

Step 1: Create Project

Start by creating an empty Android Studio project.

Step 2: Dependencies

No external dependencies are needed for this project.

Step : Write Code

MainActivity.kt

import android.content.res.ColorStateList
import android.opengl.Visibility
import android.os.Build
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.core.content.res.ResourcesCompat
import android.view.View
import android.view.ViewAnimationUtils
import kotlinx.android.synthetic.main.activity_main.*
import android.animation.Animator
import android.animation.AnimatorListenerAdapter
import kotlin.math.hypot

class MainActivity : AppCompatActivity() {

    var isOpen: Boolean = false

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        floating_button.setOnClickListener {
            revealMenu()
        }
    }

    private fun revealMenu() {
        if (!isOpen) {
            val x = main_layout.right
            val y = main_layout.bottom

            val startRadius = 0
            val endRadius = hypot(main_layout.width.toDouble(), main_layout.height.toDouble())

            floating_button.backgroundTintList = ColorStateList.valueOf(ResourcesCompat
                    .getColor(applicationContext.resources, android.R.color.white, null))
            floating_button.setImageResource(R.drawable.ic_close_black_24dp)
            if (Build.VERSION.SDK_INT >= 21) {
                val anim = ViewAnimationUtils.createCircularReveal(menu_layout,
                        x, y, startRadius.toFloat(), endRadius.toFloat())
                //duration can be custom according to you even can be left and default value will be taken
                //in ms
                anim.duration=800
                menu_layout.visibility = View.VISIBLE
                anim.start()
                isOpen = true
            } else {
                //When below API 21 for example in Kitkat
                menu_layout.visibility = View.VISIBLE
                isOpen = true
            }
        } else {
            val x = layout_text.left
            val y = layout_text.top

            val startRadius = 0
            val end = hypot(main_layout.width.toDouble(), main_layout.height.toDouble())

            floating_button.backgroundTintList = ColorStateList.valueOf(ResourcesCompat
                    .getColor(applicationContext.resources, R.color.colorPrimary, null))
            floating_button.setImageResource(R.drawable.ic_add_white_24dp)
            if (Build.VERSION.SDK_INT >= 21) {
                val anim = ViewAnimationUtils.createCircularReveal(layout_text,
                        x, y, startRadius.toFloat(), end.toFloat())
                //duration can be custom according to you even can be left and default value will be taken
                //in ms
                anim.duration=800
                anim.addListener(object : AnimatorListenerAdapter(){
                    override fun onAnimationEnd(animation: Animator?) {
                        super.onAnimationEnd(animation)
                        menu_layout.visibility = View.GONE
                    }
                })
                anim.start()
                isOpen = false
            } else {
                //When below API 21 for example in Kitkat
                menu_layout.visibility = View.GONE
                isOpen = false
            }
        }
    }
}

Run

Copy the code or download it in the link below, build and run.

Reference

Here are the reference links:

Number Link
1. Download Example
2. Follow code author
3. Code: Apache 2.0 License