Apply TextAppearance to TextPaint.

attrs.xml

<declare-styleable name="CustomView">
      <attr name="android:textAppearance"/>
</declare-styleable>

CustomView.java

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Typeface;
import android.os.Build;
import android.os.LocaleList;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.Nullable;
import androidx.annotation.StyleRes;
import androidx.core.content.res.ResourcesCompat;

import java.util.Locale;

public class CustomView extends View {
    private static final int SANS = 1;
    private static final int SERIF = 2;
    private static final int MONOSPACE = 3;

    private TextPaint textPaint = new TextPaint();
    private String text = "Hello World";
    private Rect textBounds = new Rect();

    public CustomView(Context context) {
        this(context, null);
    }

    public CustomView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);

        textPaint.setTextAlign(Paint.Align.CENTER);

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomView, 0, 0);
        int textAppearanceRes = a.getResourceId(R.styleable.CustomView_android_textAppearance, 0);
        applyTextAppearance(textAppearanceRes);
        a.recycle();
    }

    private void applyTextAppearance(@StyleRes int textAppearanceRes) {
        TypedArray appearance = getContext().getTheme().obtainStyledAttributes(textAppearanceRes,
                androidx.appcompat.R.styleable.TextAppearance);

        // text size
        int textSize = appearance.getDimensionPixelSize(
                androidx.appcompat.R.styleable.TextAppearance_android_textSize, 0);
        textPaint.setTextSize(textSize);

        // typeface
        Typeface typeface = null;
        if (appearance.hasValue(androidx.appcompat.R.styleable.TextAppearance_fontFamily)) {
            int fontId = appearance.getResourceId(
                    androidx.appcompat.R.styleable.TextAppearance_fontFamily, -1);
            if (fontId != -1) {
                typeface = ResourcesCompat.getFont(getContext(), fontId);
            } else {
                String fontFamily = appearance.getString(
                        androidx.appcompat.R.styleable.TextAppearance_android_fontFamily);
                typeface = Typeface.create(fontFamily, Typeface.NORMAL);
            }
        } else {
            int typefaceIndex = appearance.getInt(
                    androidx.appcompat.R.styleable.TextAppearance_android_typeface, -1);

            switch (typefaceIndex) {
                case SANS:
                    typeface = Typeface.SANS_SERIF;
                    break;
                case SERIF:
                    typeface = Typeface.SERIF;
                    break;
                case MONOSPACE:
                    typeface = Typeface.MONOSPACE;
                    break;
            }
        }
        int styleIndex = appearance.getInt(
                androidx.appcompat.R.styleable.TextAppearance_android_textStyle, -1);
        if (styleIndex != -1) {
            if (typeface != null) {
                typeface = Typeface.create(typeface, styleIndex);
            }
            setLabelTypeface(typeface, styleIndex);
        }

        // text shadow
        int shadowColor = appearance.getColor(
                androidx.appcompat.R.styleable.TextAppearance_android_shadowColor, 0);
        if (shadowColor != 0) {
            float shadowRadius = appearance.getFloat(
                    androidx.appcompat.R.styleable.TextAppearance_android_shadowRadius, 0f);
            float shadowDx = appearance.getFloat(
                    androidx.appcompat.R.styleable.TextAppearance_android_shadowDx, 0f);
            float shadowDy = appearance.getFloat(
                    androidx.appcompat.R.styleable.TextAppearance_android_shadowDy, 0f);
            textPaint.setShadowLayer(shadowRadius, shadowDx, shadowDy, shadowColor);
        }

        // text locale
        String localeText = appearance.getString(
                androidx.appcompat.R.styleable.TextAppearance_textLocale);
        if (localeText != null && localeText.equals("")) {
            final String[] tags = localeText.split(",");
            final Locale[] localeArray = new Locale[tags.length];
            for (int i = 0; i < localeArray.length; i++) {
                localeArray[i] = Locale.forLanguageTag(tags[i]);
            }

            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
                textPaint.setTextLocale(localeArray[0]);
            } else {
                textPaint.setTextLocales(new LocaleList(localeArray));
            }
        }

        appearance.recycle();
    }

    private void setLabelTypeface(Typeface typeface, int style) {
        if (style > 0) {
            if (typeface == null) {
                typeface = Typeface.defaultFromStyle(style);
            } else {
                typeface = Typeface.create(typeface, style);
            }

            setLabelTypeface(typeface);
            // now compute what (if any) algorithmic styling is needed
            int typefaceStyle = typeface != null ? typeface.getStyle() : 0;
            int need = style & ~typefaceStyle;
            textPaint.setFakeBoldText((need & Typeface.BOLD) != 0);
            textPaint.setTextSkewX((need & Typeface.ITALIC) != 0 ? -0.25f : 0);
        } else {
            textPaint.setFakeBoldText(false);
            textPaint.setTextSkewX(0);
            setLabelTypeface(typeface);
        }
    }

    private void setLabelTypeface(Typeface typeface) {
        if ((textPaint.getTypeface() != null && !textPaint.getTypeface().equals(typeface))
                || (textPaint.getTypeface() == null && typeface != null)) {
            textPaint.setTypeface(typeface);
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        int width = getWidth();
        int height = getHeight();
        float baselineX = width / 2f;
        float baselineY;

        textPaint.getTextBounds(text, 0, text.length(), textBounds);
        baselineY = (height / 2f) - textBounds.exactCenterY();

        canvas.drawText(text, baselineX, baselineY, textPaint);
    }
}