How to use specified weights for fonts in XML

Question

Using the Fonts in XML feature you can specify various font weights for a font family. For example:

<?xml version="1.0" encoding="utf-8"?>
<font-family xmlns:android="http://schemas.android.com/apk/res/android"
             xmlns:app="http://schemas.android.com/apk/res-auto">

    <font android:font="@font/archivo_narrow_regular" android:fontWeight="400" android:fontStyle="normal"
        app:font="@font/archivo_narrow_regular" app:fontWeight="400" app:fontStyle="normal"/>

    <font android:font="@font/archivo_narrow_regular_italic" android:fontWeight="400" android:fontStyle="italic"
        app:font="@font/archivo_narrow_regular_italic" app:fontWeight="400" app:fontStyle="italic"/>

    <font android:font="@font/archivo_narrow_medium" android:fontWeight="500" android:fontStyle="normal"
        app:font="@font/archivo_narrow_medium" app:fontWeight="500" app:fontStyle="normal"/>

    <font android:font="@font/archivo_narrow_medium_italic" android:fontWeight="500" android:fontStyle="italic"
        app:font="@font/archivo_narrow_medium_italic" app:fontWeight="500" app:fontStyle="italic"/>

    <font android:font="@font/archivo_narrow_semibold" android:fontWeight="600" android:fontStyle="normal"
        app:font="@font/archivo_narrow_semibold" app:fontWeight="600" app:fontStyle="normal"/>

    <font android:font="@font/archivo_narrow_semibold_italic" android:fontWeight="600" android:fontStyle="italic"
        app:font="@font/archivo_narrow_semibold_italic" app:fontWeight="600" app:fontStyle="italic"/>

    <font android:font="@font/archivo_narrow_bold" android:fontWeight="700" android:fontStyle="normal"
        app:font="@font/archivo_narrow_bold" app:fontWeight="700" app:fontStyle="normal"/>

    <font android:font="@font/archivo_narrow_bold_italic" android:fontWeight="700" android:fontStyle="italic"
        app:font="@font/archivo_narrow_bold_italic" app:fontWeight="700" app:fontStyle="italic"/>

</font-family>

But I cannot figure out how to actually make use of each of these weights; either in an XML (layout/style) file, or in Java code. Their is no fontWeight attribute available for TextView, and the Typeface object created from ResourcesCompat.getFont(context, R.font.archivo_narrow) has no mention of font weights.

I realize that I can just specify the specific font resource (i.e. R.font.archivo_narrow_semibold), but then what is the point of having a fontWeight attribute in the font-family?

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Update

A new static create(Typeface family, int weight, boolean italic) method was added in API Level 28, along with a getWeight() instance method. This finally makes it possible to make use of the fontWeight attribute in Java code; though only for API Level 28 and above, I haven't found any analogs in the support library.

This is useful—and shows that the fontWeight attribute didn't serve any purpose in the past—but I would really like to be able to use the weight in XML styling.

Answer 1

Its looks like android following web standards for font management and sizing for android app.

The “font-weight” property is used to define the weight of a font, such as regular or bold.

But for all other weights a numerical range from 100 to 900 is used. One of the challenges with web fonts is that most web browsers do not properly support font weights other than normal & bold. The following chart describes the possible mappings of weights to the numeric definitions:

100    Extra Light or Ultra Light
200    Light or Thin
300    Book or Demi
400    Normal or Regular
500    Medium
600    Semibold, Demibold
700    Bold
800    Black, Extra Bold or Heavy
900    Extra Black, Fat, Poster or Ultra Black

You can read more about font weight here

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cc_montserrat_bold.xml

<?xml version="1.0" encoding="utf-8"?>
<font-family xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <font
        android:font="@font/montserrat_bold"
        android:fontStyle="normal"
        android:fontWeight="700"
        app:font="@font/montserrat_bold"
        app:fontStyle="normal"
        app:fontWeight="700" />
    <font
        android:font="@font/montserrat_bolditalic"
        android:fontStyle="italic"
        android:fontWeight="700"
        app:font="@font/montserrat_bolditalic"
        app:fontStyle="italic"
        app:fontWeight="700" />

</font-family>

cc_montserrat_regular.xml

<?xml version="1.0" encoding="utf-8"?>
<font-family xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <font
        android:font="@font/montserrat_regular"
        android:fontStyle="normal"
        android:fontWeight="400"
        app:font="@font/montserrat_regular"
        app:fontStyle="normal"
        app:fontWeight="400" />
    <font
        android:font="@font/montserrat_italic"
        android:fontStyle="italic"
        android:fontWeight="400"
        app:font="@font/montserrat_italic"
        app:fontStyle="italic"
        app:fontWeight="400" />


</font-family>

Kotlin Usage:

val textView = dialog.findViewById<TextView>(android.R.id.message) as TextView
val typeface = ResourcesCompat.getFont(context,R.font.cc_montserrat_regular)
        textView.typeface = typeface

Android Project Screenshot: