Loading custom fonts can be lead to a bad performance. I highly recommend to use this little helper which saves/loads your already used fonts into a Hashtable.

public class TypefaceUtils {

private static final Hashtable<String, Typeface> sTypeFaces = new Hashtable<>();

/**
 * Get typeface by filename from assets main directory
 *
 * @param context
 * @param fileName the name of the font file in the asset main directory
 * @return
 */
public static Typeface getTypeFace(final Context context, final String fileName) {
    Typeface tempTypeface = sTypeFaces.get(fileName);

    if (tempTypeface == null) {
        tempTypeface = Typeface.createFromAsset(context.getAssets(), fileName);
        sTypeFaces.put(fileName, tempTypeface);
    }

    return tempTypeface;
}

}

Usage:

Typeface typeface = TypefaceUtils.getTypeface(context, "RobotoSlab-Bold.ttf");
setTypeface(typeface);