Rounded Background Span

rounded_background_span.kt

import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.Paint.FontMetricsInt
import android.graphics.RectF
import android.text.style.LineHeightSpan
import android.text.style.ReplacementSpan

/**
 * A span to create a rounded background on a text.
 *
 * If radius is set, it generates a rounded background.
 * If radius is null, it generates a circle background.
 */
class RoundedBackgroundSpan (
    private val backgroundColor: Int,
    private val textColor: Int,
    private val padding: Int = 16,
    private val radius: Float? = null) : ReplacementSpan(),

    LineHeightSpan {
        override fun getSize(paint: Paint, text: CharSequence?, start: Int, end: Int, fm: FontMetricsInt?): Int {
            return (padding + paint.measureText(text, start, end) + padding).toInt()
        }

        override fun draw(
            canvas: Canvas,
            text: CharSequence?,
            start: Int,
            end: Int,
            x: Float,
            top: Int,
            y: Int,
            bottom: Int,
            paint: Paint
        ) {
            paint.color = backgroundColor

            val width = paint.measureText(text, start, end)
            val height = paint.fontMetrics.descent - paint.fontMetrics.ascent + 2 * padding

            if(radius != null) {
                val rect = RectF(x, top.toFloat(), x + width + 2 * padding, bottom.toFloat())
                canvas.drawRoundRect(rect, radius, radius, paint)
            } else {
                canvas.drawCircle(x + ((width + 2 * padding) / 2), ((bottom - top) / 2).toFloat(), height / 2, paint)
            }

            paint.color = textColor
            canvas.drawText(text, start, end, x + padding, y.toFloat(), paint)
        }

        override fun chooseHeight(
            text: CharSequence?,
            start: Int,
            end: Int,
            spanstartv: Int,
            lineHeight: Int,
            fm: FontMetricsInt?
        ) {}
    }

spannable = SpannableString(CalendarUtil.getShortWeekday(i, firstDayOfWeek))
spannable.setSpan(RoundedBackgroundSpan(backGroundColor, textColor, 24, null),0, 1,Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
textView.setText(spannable);