SpannableString 之居中显示 ImageSpan

自定义布局：SpannableString 之居中显示 ImageSpan

class CenteredImageSpan(context: Context, drawableRes: Int) : ImageSpan(context, drawableRes) {
    override fun draw(
        canvas: Canvas,
        text: CharSequence,
        start: Int,
        end: Int,
        x: Float,
        top: Int,
        y: Int,
        bottom: Int,
        paint: Paint
    ) {
        // image to draw
        val b = drawable
        // font metrics of text to be replaced
        val fm = paint.fontMetricsInt
        var transY = ((y + fm.descent + y + fm.ascent) / 2 - b.bounds.bottom / 2)
        // to check the last line.(当 image 在单独一行显示时可能会存在这个问题）
        if (transY > bottom - b.bounds.bottom) transY = bottom - b.bounds.bottom
        canvas.save()
        canvas.translate(x, transY.toFloat())
        b.draw(canvas)
        canvas.restore()
    }
}

val spanStr = SpannableStringBuilder()
spanStr.append("# ")
spanStr.append(title)
val imageSpan = CenteredImageSpan(this, R.mipmap.ic_topic_detail_jinghao_black)
spanStr.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
// corner
spanStr.append(" #")
val len = spanStr.length
val cornerSpan = CenteredImageSpan(this,  R.mipmap.ic_topic_detail_remen)
spanStr.setSpan(cornerSpan, len - 1, len, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
binding.ctTalkDetailInfo.talkNameTv.text = spanStr