How to get line count of textview before rendering?

Question

How can I get the number of lines a string will take up in a TextView before it is rendered.

A ViewTreeObserver will not work because thos

Answer 1

Thanks to Eugene Popovich I got:

import android.os.Build
import android.text.Layout
import android.text.StaticLayout
import android.text.TextDirectionHeuristic
import android.text.TextPaint
import android.widget.TextView


object TextMeasurementUtil {
    /**
     * Split text into lines using specified parameters and the same algorithm
     * as used by the [TextView] component
     *
     * @param text   the text to split
     * @param params the measurement parameters
     * @return
     */
    fun getTextLines(text: CharSequence, params: TextViewParams): List {
        val layout = getStaticLayout(text, params)
        return (0 until layout.lineCount).map {
            layout.text.subSequence(layout.getLineStart(it), layout.getLineEnd(it))
        }
    }

    fun getTextLineCount(text: CharSequence, params: TextViewParams): Int {
        val layout = getStaticLayout(text, params)
        return layout.lineCount
    }

    fun getTextLines(textView: TextView): List {
        val layout = getStaticLayout(textView)
        return (0 until layout.lineCount).map {
            layout.text.subSequence(layout.getLineStart(it), layout.getLineEnd(it))
        }
    }

    fun getTextLineCount(textView: TextView): Int {
        val layout = getStaticLayout(textView)
        return layout.lineCount
    }

    /**
     * The text measurement parameters
     */
    fun getTextViewParams(textView: TextView): TextViewParams {
        val layout = textView.layout
        val width = textView.width - textView.compoundPaddingLeft - textView.compoundPaddingRight
        var lineSpacingExtra = 0f
        var lineSpacingMultiplier = 1.0f
        var includeFontPadding = true
        var breakStrategy = 0
        var hyphenationFrequency = 0
        var justificationMode = 0
        var useFallbackLineSpacing = false
        var textDirectionHeuristic: TextDirectionHeuristic? = null

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            lineSpacingExtra = textView.lineSpacingExtra
            lineSpacingMultiplier = textView.lineSpacingMultiplier
            includeFontPadding = textView.includeFontPadding
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                breakStrategy = textView.breakStrategy
                hyphenationFrequency = textView.hyphenationFrequency
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                justificationMode = textView.justificationMode
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
                useFallbackLineSpacing = textView.isFallbackLineSpacing
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                textDirectionHeuristic = textView.textDirectionHeuristic
            }
        }

        return TextViewParams(
            textPaint = layout.paint,
            alignment = layout.alignment,
            lineSpacingExtra = lineSpacingExtra,
            lineSpacingMultiplier = lineSpacingMultiplier,
            includeFontPadding = includeFontPadding,
            breakStrategy = breakStrategy,
            hyphenationFrequency = hyphenationFrequency,
            justificationMode = justificationMode,
            useFallbackLineSpacing = useFallbackLineSpacing,
            textDirectionHeuristic = textDirectionHeuristic,
            width = width
        )
    }

    private fun getStaticLayout(text: CharSequence,
                                params: TextViewParams): StaticLayout =
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            val builder = StaticLayout.Builder
                .obtain(text, 0, text.length, params.textPaint, params.width)
                .setAlignment(params.alignment)
                .setLineSpacing(params.lineSpacingExtra, params.lineSpacingMultiplier)
                .setIncludePad(params.includeFontPadding)
                .setBreakStrategy(params.breakStrategy)
                .setHyphenationFrequency(params.hyphenationFrequency)
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                builder.setJustificationMode(params.justificationMode)
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
                builder.setUseLineSpacingFromFallbacks(params.useFallbackLineSpacing)
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                builder.setTextDirection(params.textDirectionHeuristic!!)
            }
            builder.build()
        } else {
            @Suppress("DEPRECATION")
            StaticLayout(
                text,
                params.textPaint,
                params.width,
                params.alignment,
                params.lineSpacingMultiplier,
                params.lineSpacingExtra,
                params.includeFontPadding)
        }

    private fun getStaticLayout(textView: TextView): StaticLayout =
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            val builder = StaticLayout.Builder
                .obtain(textView.text, 0, textView.text.length, textView.layout.paint,
                    textView.width)
                .setAlignment(textView.layout.alignment)
                .setLineSpacing(textView.lineSpacingExtra, textView.lineSpacingMultiplier)
                .setIncludePad(textView.includeFontPadding)
                .setBreakStrategy(textView.breakStrategy)
                .setHyphenationFrequency(textView.hyphenationFrequency)
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                builder.setJustificationMode(textView.justificationMode)
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
                builder.setUseLineSpacingFromFallbacks(textView.isFallbackLineSpacing)
            }
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                builder.setTextDirection(textView.textDirectionHeuristic)
            }
            builder.build()
        } else {
            @Suppress("DEPRECATION")
            StaticLayout(
                textView.text,
                textView.layout.paint,
                textView.width,
                textView.layout.alignment,
                textView.lineSpacingMultiplier,
                textView.lineSpacingExtra,
                textView.includeFontPadding)
        }

    data class TextViewParams(
        val textPaint: TextPaint,
        val alignment: Layout.Alignment,
        val lineSpacingExtra: Float,
        val lineSpacingMultiplier: Float,
        val includeFontPadding: Boolean,
        val breakStrategy: Int,
        val hyphenationFrequency: Int,
        val justificationMode: Int,
        val useFallbackLineSpacing: Boolean,
        val textDirectionHeuristic: TextDirectionHeuristic?,
        val width: Int
    )
}

Usage:

1. If you want to print different texts in equal TextViews (for instance, in RecyclerView with one or similar ViewHolders):

    val params = TextMeasurementUtil.getTextViewParams(textView)
   
    val lines = TextMeasurementUtil.getTextLines(textView.text, params)
    val count = TextMeasurementUtil.getTextLineCount(textView.text, params)
   

2. In any other case:

    val lines = TextMeasurementUtil.getTextLines(textView)
    val count = TextMeasurementUtil.getTextLineCount(textView)
   

In RecyclerView you won't know parameters of TextView until you call post or doOnPreDraw method, so use:

textView.doOnPreDraw {
    val lines = TextMeasurementUtil.getTextLines(textView)
    val count = TextMeasurementUtil.getTextLineCount(textView)
}