TextView.setExpandableText

gistfile1.txt

fun TextView.setExpandableText(text: String, maxLines: Int, buttonsOnNewLines: Boolean = false) {
    var layoutLaid = false
    var layoutDisposable: Disposable? = null

    setText(text)
    post {
        // If more than max lines are to be used for text, use "more-less" clickable
        // labels in order to expand and collapse the text
        if (lineCount > maxLines) {
            // Temporarily set these values on the TextView.
            // After layout is laid, we'll be able to compute the number of characters
            // truncated from the text in order to add the "More" clickable label.
            ellipsize = TextUtils.TruncateAt.END
            setMaxLines(maxLines)

            layoutDisposable = globalLayouts().subscribeLoggingErrors(onNext = {
                if (isLaidOut && !layoutLaid) {
                    layoutLaid = true
                    layoutDisposable?.dispose()
                    val truncatedCharacters = layout.getEllipsisCount(layout.lineCount - 1)

                    if (truncatedCharacters > 0) {
                        val more = context.getString(R.string.more)
                        val less = context.getString(R.string.less)
                        // Additional characters to cut from text,
                        // initially was 1 (for the space between the ellipsis and the "More" label),
                        // but after testing, 5 gives a more correct visual result
                        val additionalCut = 5
                        val truncatedText = if (buttonsOnNewLines) {
                            String.format("%s…\n%s", text.substring(0, text.length - truncatedCharacters - more.length - additionalCut), more)
                        } else {
                            String.format("%s… %s", text.substring(0, text.length - truncatedCharacters - more.length - additionalCut), more)
                        }
                        val fullText = if (buttonsOnNewLines) {
                            String.format("%s\n%s", text, less)
                        } else {
                            String.format("%s %s", text, less)
                        }
                        val truncatedSpannable = SpannableStringBuilder(truncatedText)
                        val fullSpannable = SpannableStringBuilder(fullText)

                        truncatedSpannable.setSpan(object : ClickableSpan() {
                            override fun onClick(widget: View) {
                                setText(fullSpannable, TextView.BufferType.SPANNABLE)
                            }
                        }, truncatedText.length - more.length, truncatedText.length, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

                        fullSpannable.setSpan(object : ClickableSpan() {
                            override fun onClick(widget: View) {
                                setText(truncatedSpannable, TextView.BufferType.SPANNABLE)
                            }
                        }, fullText.length - less.length, fullText.length, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

                        // Won't be using the ellipsize and maxLines attributes anymore
                        ellipsize = null
                        setMaxLines(Integer.MAX_VALUE)

                        // Start with the truncated text
                        setText(truncatedSpannable, TextView.BufferType.SPANNABLE)
                        movementMethod = LinkMovementMethod.getInstance()
                    }
                }
            })
        }
    }
}

Use as
text_description.setExpandableText(bigTextDescription, maxLines = 2, buttonsOnNewLines = true)