Android Custom font Spannable Typeface Span

I am using Helvetica fonts throughout my application. Currently I am creating the fonts separately from assets. So I have say these three

HelveticaNeue = Typeface.createFromAsset(application.getAssets(), "fonts/HelveticaNeue.ttf");
HelveticaNeueBold = Typeface.createFromAsset(application.getAssets(), "fonts/HelveticaNeueBold.ttf");
HelveticaNeueBoldItalic = Typeface.createFromAsset(application.getAssets(), "fonts/HelveticaNeueBoldItalic.ttf");

Everything works great when I use one typeface for one TextView. However, I need to use a spannable

Spannable WordtoSpan = new SpannableString("This text should be normal, but this needs to be bold, and normal");    
WordtoSpan.setSpan(new Typefac开发者_StackOverfloweSpan("bold"), 5, 7, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

And I want to have part of the string be HeleveticaNeueBold and some be just HelveticaNeue. I think what is needed is to indicate to Android that the 3 fonts above are actually related so that it can switch them nicely. Looking for any other way of doing this as well.

You are going to want to write a custom TypefaceSpan. The good news is that they aren't difficult. See here for an example.

You can do the following:

SpannableString spannableString = new SpannableString("your text");
Typeface typeface = Typeface.create(ResourcesCompat.getFont(this, R.font.your_font);
spannableString.setSpan(
    new TypefaceSpan(typeface, Typeface.NORMAL)), 
    0, 4, 
    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);

This constructor will replace the previous style of the text, achieving what you want. However, the catch is that it was introduced in API 28.