ProgressView.kt

import android.animation.Animator
import android.animation.ValueAnimator
import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.graphics.RectF
import android.support.annotation.ColorRes
import android.util.AttributeSet
import android.util.TypedValue
import android.view.View

class ProgressView @JvmOverloads constructor(context: Context,
                                             attrs: AttributeSet? = null,
                                             defStyleAttr: Int = 0,
                                             defStyleRes: Int = 0) : View(context, attrs, defStyleAttr, defStyleRes) {

    private val trackPaint = Paint()
    private val progressPaint = Paint()
    private val rectF = RectF()
    private var progress = 0.0
    private var animation: ValueAnimator? = null

    private val animatorListener = object : Animator.AnimatorListener {
        override fun onAnimationRepeat(p0: Animator?) {
        }

        override fun onAnimationCancel(p0: Animator?) {
        }

        override fun onAnimationStart(p0: Animator?) {
        }

        override fun onAnimationEnd(p0: Animator?) {
            onAnimationFinished?.invoke()
        }
    }

    @ColorRes
    var trackColor = Color.LTGRAY
    @ColorRes
    var progressColor = Color.GRAY
    var trackWidth = 15f
    var onAnimationFinished: (() -> Unit)? = null

    init {

        val trackWidth = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, trackWidth, resources.displayMetrics)

        trackPaint.color = trackColor
        trackPaint.isAntiAlias = true
        trackPaint.style = Paint.Style.STROKE
        trackPaint.strokeWidth = trackWidth

        progressPaint.color = progressColor
        progressPaint.isAntiAlias = true
        progressPaint.style = Paint.Style.STROKE
        progressPaint.strokeWidth = trackWidth
        progressPaint.strokeCap = Paint.Cap.ROUND
    }

    fun setProgress(newProgress: Double, duration: Long = 500) {
        animation?.cancel()

        animation = ValueAnimator.ofFloat(progress.toFloat(), newProgress.toFloat())
        animation?.duration = duration
        animation?.addUpdateListener {
            progress = (it.animatedValue as Float).toDouble()
            invalidate()
        }
        animation?.addListener(animatorListener)
        animation?.start()

        invalidate()
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)

        val longestSide = if (measuredHeight < measuredWidth) measuredHeight else measuredWidth

        val arcBounds = (longestSide * (0.004 * trackWidth)).toInt()
        rectF.set(arcBounds.toFloat(), arcBounds.toFloat(), (longestSide - arcBounds).toFloat(), (longestSide - arcBounds).toFloat())
    }

    override fun onDraw(canvas: Canvas?) {
        canvas?.drawArc(rectF, -90f, 360f, false, trackPaint)
        canvas?.drawArc(rectF, -90f, 360f / 100 * (progress.toFloat()), false, progressPaint)
    }
}