ProgressBar.kt

package com.robertlevonyan.demo.progressbar

import android.animation.AnimatorSet
import android.animation.ValueAnimator
import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.util.AttributeSet
import android.view.View
import androidx.core.animation.doOnEnd

class ProgressBar @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0,
    defStyleRes: Int = 0
) : View(context, attrs, defStyleAttr, defStyleRes) {
    companion object {
        private const val INITIAL_WIDTH = 10f
        private const val TARGET_WIDTH = 200f
    }

    private val bgPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        color = Color.LTGRAY
    }
    private val progressPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        color = Color.YELLOW
    }

    private var progressLeft = INITIAL_WIDTH
    private var progressRight = INITIAL_WIDTH

    private val widthStartAnimation by lazy {
        ValueAnimator.ofFloat(progressLeft, TARGET_WIDTH).apply {
            duration = 300
            addUpdateListener {
                progressRight = it.animatedValue as Float
                invalidate()
            }
        }
    }
    private val translateAnimation by lazy {
        val end = width - 10 - TARGET_WIDTH
        ValueAnimator.ofFloat(progressLeft, end).apply {
            duration = 800
            startDelay = 250
            addUpdateListener {
                val translationValue = it.animatedValue as Float
                progressLeft = translationValue
                progressRight = translationValue + TARGET_WIDTH
                invalidate()
            }
        }
    }

    private val widthEndAnimation by lazy {
        ValueAnimator.ofFloat(TARGET_WIDTH, INITIAL_WIDTH).apply {
            startDelay = 1000
            addUpdateListener {
                progressLeft = width - it.animatedValue as Float
                invalidate()
            }
        }
    }

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)
        canvas ?: return

        val (left, top) = INITIAL_WIDTH to height / 2f + INITIAL_WIDTH
        val (right, bottom) = width - INITIAL_WIDTH to height / 2f - INITIAL_WIDTH
        val (rx, ry) = height / 2f to height / 2f

        // draw background
        canvas.drawRoundRect(left, top, right, bottom, rx, ry, bgPaint)

        // draw progress
        canvas.drawRoundRect(progressLeft, top, progressRight, bottom, rx, ry, progressPaint)
    }

    fun startAnimation() {
        post {
            AnimatorSet()
                .apply {
                    playTogether(widthStartAnimation, translateAnimation, widthEndAnimation)
                    doOnEnd {
                        progressLeft = INITIAL_WIDTH
                        progressRight = INITIAL_WIDTH
                        it.start()
                    }
                }
                .start()
        }
    }
}