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

The @denis-kniazhev answer is very good. However it uses custom logic to break text into lines. It is possible to use standard TextView layout components to measure text.

That is how it may look like:

TextView myTextView = findViewById(R.id.text);
TextMeasurementUtils.TextMeasurementParams params = TextMeasurementUtils.TextMeasurementParams.Builder
.from(myTextView).build();
List lines = TextMeasurementUtils.getTextLines(text, params);

TextMeasurementUtils.java

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

import java.util.ArrayList;
import java.util.List;

public class TextMeasurementUtils {
    /**
     * Split text into lines using specified parameters and the same algorithm
     * as used by the {@link TextView} component
     *
     * @param text   the text to split
     * @param params the measurement parameters
     * @return
     */
    public static List getTextLines(CharSequence text, TextMeasurementParams params) {
        StaticLayout layout;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            StaticLayout.Builder 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((TextDirectionHeuristic) params.textDirectionHeuristic);
            }
            layout = builder.build();
        } else {
            layout = new StaticLayout(
                    text,
                    params.textPaint,
                    params.width,
                    params.alignment,
                    params.lineSpacingMultiplier,
                    params.lineSpacingExtra,
                    params.includeFontPadding);
        }
        List result = new ArrayList<>();
        for (int i = 0; i < layout.getLineCount(); i++) {
            result.add(layout.getText().subSequence(layout.getLineStart(i), layout.getLineEnd(i)));
        }
        return result;
    }

    /**
     * The text measurement parameters
     */
    public static class TextMeasurementParams {
        public final TextPaint textPaint;
        public final Layout.Alignment alignment;
        public final float lineSpacingExtra;
        public final float lineSpacingMultiplier;
        public final boolean includeFontPadding;
        public final int breakStrategy;
        public final int hyphenationFrequency;
        public final int justificationMode;
        public final boolean useFallbackLineSpacing;
        public final Object textDirectionHeuristic;
        public final int width;

        private TextMeasurementParams(Builder builder) {
            textPaint = requireNonNull(builder.textPaint);
            alignment = requireNonNull(builder.alignment);
            lineSpacingExtra = builder.lineSpacingExtra;
            lineSpacingMultiplier = builder.lineSpacingMultiplier;
            includeFontPadding = builder.includeFontPadding;
            breakStrategy = builder.breakStrategy;
            hyphenationFrequency = builder.hyphenationFrequency;
            justificationMode = builder.justificationMode;
            useFallbackLineSpacing = builder.useFallbackLineSpacing;
            textDirectionHeuristic = builder.textDirectionHeuristic;
            width = builder.width;
        }


        public static final class Builder {
            private TextPaint textPaint;
            private Layout.Alignment alignment;
            private float lineSpacingExtra;
            private float lineSpacingMultiplier = 1.0f;
            private boolean includeFontPadding = true;
            private int breakStrategy;
            private int hyphenationFrequency;
            private int justificationMode;
            private boolean useFallbackLineSpacing;
            private Object textDirectionHeuristic;
            private int width;

            public Builder() {
            }

            public Builder(TextMeasurementParams copy) {
                this.textPaint = copy.textPaint;
                this.alignment = copy.alignment;
                this.lineSpacingExtra = copy.lineSpacingExtra;
                this.lineSpacingMultiplier = copy.lineSpacingMultiplier;
                this.includeFontPadding = copy.includeFontPadding;
                this.breakStrategy = copy.breakStrategy;
                this.hyphenationFrequency = copy.hyphenationFrequency;
                this.justificationMode = copy.justificationMode;
                this.useFallbackLineSpacing = copy.useFallbackLineSpacing;
                this.textDirectionHeuristic = copy.textDirectionHeuristic;
                this.width = copy.width;
            }

            public static Builder from(TextView view) {
                Layout layout = view.getLayout();
                Builder result = new Builder()
                        .textPaint(layout.getPaint())
                        .alignment(layout.getAlignment())
                        .width(view.getWidth() -
                                view.getCompoundPaddingLeft() - view.getCompoundPaddingRight());
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                    result.lineSpacingExtra(view.getLineSpacingExtra())
                            .lineSpacingMultiplier(view.getLineSpacingMultiplier())
                            .includeFontPadding(view.getIncludeFontPadding());
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        result.breakStrategy(view.getBreakStrategy())
                                .hyphenationFrequency(view.getHyphenationFrequency());
                    }
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                        result.justificationMode(view.getJustificationMode());
                    }
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
                        result.useFallbackLineSpacing(view.isFallbackLineSpacing());
                    }
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                        result.textDirectionHeuristic(view.getTextDirectionHeuristic());
                    }
                }
                return result;
            }

            public Builder textPaint(TextPaint val) {
                textPaint = val;
                return this;
            }

            public Builder alignment(Layout.Alignment val) {
                alignment = val;
                return this;
            }

            public Builder lineSpacingExtra(float val) {
                lineSpacingExtra = val;
                return this;
            }

            public Builder lineSpacingMultiplier(float val) {
                lineSpacingMultiplier = val;
                return this;
            }

            public Builder includeFontPadding(boolean val) {
                includeFontPadding = val;
                return this;
            }

            public Builder breakStrategy(int val) {
                breakStrategy = val;
                return this;
            }

            public Builder hyphenationFrequency(int val) {
                hyphenationFrequency = val;
                return this;
            }

            public Builder justificationMode(int val) {
                justificationMode = val;
                return this;
            }

            public Builder useFallbackLineSpacing(boolean val) {
                useFallbackLineSpacing = val;
                return this;
            }

            public Builder textDirectionHeuristic(Object val) {
                textDirectionHeuristic = val;
                return this;
            }

            public Builder width(int val) {
                width = val;
                return this;
            }

            public TextMeasurementParams build() {
                return new TextMeasurementParams(this);
            }
        }
    }

    public static  T requireNonNull(T obj) {
      if (obj == null)
          throw new NullPointerException();
      return obj;
    }
}