star_progress

/**
 * Виджет "звездного" прогресс-бара.
 * 
 * Для корректной работы необходимо в рантайме задать значение [@see totalProgress], а затем задать 
 * актуальное значение [@see currentProgress].
 * 
 * Четыре цвета градиента задаются через XML-атрибуты:
 * * [@see ProgressStarView_psv_color_start]
 * * [@see ProgressStarView_psv_color_middle_1]
 * * [@see ProgressStarView_psv_color_middle_2]
 * * [@see ProgressStarView_psv_color_end]
 */
class ProgressStarView(context: Context?, attrs: AttributeSet?) : View(context, attrs) {

    //общий прогресс
    var totalProgress: Int = 10
        set(value) {
            field = when {
                value < 0 -> 0
                else -> value
            }
            invalidate()
        }

    //текущий прогресс
    var currentProgress: Int = 9
        set(value) {
            field = when {
                value > totalProgress -> totalProgress
                value < 0 -> 0
                else -> value
            }
            invalidate()
        }

    private var viewWidth: Int = 0
    private var viewHeight: Int = 0

    //толщина линии контура звезды
    private var starStrokeWidth: Float = 0F
        get() = (viewWidth / 24).toFloat()

    private val paint = Paint()
    private var gradientColors = intArrayOf()
    private var linearGradient: LinearGradient? = null

    private var starStrokePath = Path()
    private var progressPath = Path()

    init {
        obtainAttributes(attrs)

        //инициализация "кисточки"
        paint.apply {
            isAntiAlias = true
            strokeCap = Paint.Cap.ROUND     //закругление окончаний примитивов
            strokeJoin = Paint.Join.ROUND   //закругление узлов сопряжения
            style = Paint.Style.STROKE      //отрисовка границы без заливки
        }
    }

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

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        viewWidth = MeasureSpec.getSize(widthMeasureSpec)
        viewHeight = MeasureSpec.getSize(heightMeasureSpec)
        prepareGradientFill()
    }

    private fun obtainAttributes(attrs: AttributeSet?) {
        attrs ?: return

        val ta = context.obtainStyledAttributes(attrs, R.styleable.ProgressStarView)
        val colorStart = ta.getColor(R.styleable.ProgressStarView_psv_color_start, Color.BLACK)
        val colorMiddle1 = ta.getColor(R.styleable.ProgressStarView_psv_color_middle_1, Color.BLACK)
        val colorMiddle2 = ta.getColor(R.styleable.ProgressStarView_psv_color_middle_2, Color.BLACK)
        val colorEnd = ta.getColor(R.styleable.ProgressStarView_psv_color_end, Color.BLACK)
        ta.recycle()

        this.gradientColors = intArrayOf(colorStart, colorMiddle1, colorMiddle2, colorEnd)
    }

    /**
     * Отрисовка контура звезды.
     */
    private fun drawStarStroke(canvas: Canvas) {
        paint.strokeWidth = starStrokeWidth
        paint.color = ContextCompat.getColor(context, R.color.bossanova_light)
        
        starStrokePath.moveTo(viewWidth * 0.5f, viewHeight * 0.029f) //1
        starStrokePath.quadTo(viewWidth * 0.545f, viewHeight * 0.029f, viewWidth * 0.566f, viewHeight * 0.072f) //2
        starStrokePath.lineTo(viewWidth * 0.666f, viewHeight * 0.295f) //3
        starStrokePath.lineTo(viewWidth * 0.909f, viewHeight * 0.331f) //4
        starStrokePath.quadTo(viewWidth * 0.954f, viewHeight * 0.338f, viewWidth * 0.968f, viewHeight * 0.383f) //5
        starStrokePath.quadTo(viewWidth * 0.982f, viewHeight * 0.428f, viewWidth * 0.949f, viewHeight * 0.461f) //6
        starStrokePath.lineTo(viewWidth * 0.778f, viewHeight * 0.635f) //7
        starStrokePath.lineTo(viewWidth * 0.818f, viewHeight * 0.88f) //8
        starStrokePath.quadTo(viewWidth * 0.826f, viewHeight * 0.928f, viewWidth * 0.789f, viewHeight * 0.955f) //9
        starStrokePath.quadTo(viewWidth * 0.752f, viewHeight * 0.983f, viewWidth * 0.711f, viewHeight * 0.961f) //10
        starStrokePath.lineTo(viewWidth * 0.5f, viewHeight * 0.845f) //11
        starStrokePath.lineTo(viewWidth * 0.288f, viewHeight * 0.961f) //12
        starStrokePath.quadTo(viewWidth * 0.246f, viewHeight * 0.983f, viewWidth * 0.21f, viewHeight * 0.955f) //13
        starStrokePath.quadTo(viewWidth * 0.173f, viewHeight * 0.928f, viewWidth * 0.181f, viewHeight * 0.88f) //14
        starStrokePath.lineTo(viewWidth * 0.221f, viewHeight * 0.635f) //15
        starStrokePath.lineTo(viewWidth * 0.05f, viewHeight * 0.461f) //16
        starStrokePath.quadTo(viewWidth * 0.016f, viewHeight * 0.428f, viewWidth * 0.031f, viewHeight * 0.383f) //17
        starStrokePath.quadTo(viewWidth * 0.045f, viewHeight * 0.338f, viewWidth * 0.09f, viewHeight * 0.331f) //18
        starStrokePath.lineTo(viewWidth * 0.327f, viewHeight * 0.295f) //19
        starStrokePath.quadTo(viewWidth * 0.454f, viewHeight * 0.029f, viewWidth * 0.5f, viewHeight * 0.029f) //20

        paint.shader = null
        canvas.drawPath(starStrokePath, paint)

        val pathMeasure = PathMeasure(starStrokePath, false)
        val currentProgressLength =
                pathMeasure.length * (currentProgress.toFloat() / totalProgress.toFloat())
        progressPath.rewind()
        pathMeasure.getSegment(0f, currentProgressLength, progressPath, true)
        paint.shader = linearGradient
        canvas.drawPath(progressPath, paint)
    }

    /**
     * Подготовка градиентной заливки прогресс-бара.
     */
    private fun prepareGradientFill() {
        if (linearGradient == null) {
            linearGradient = LinearGradient(
                    viewWidth * 0.208f,
                    viewWidth * 0.220f,
                    viewWidth.toFloat(),
                    viewHeight.toFloat(),
                    gradientColors,
                    null,
                    Shader.TileMode.CLAMP
            )
        }
    }
}