Extended FAB using Material Components on Android

layout_with_fab.xml

<?xml version="1.0" encoding="utf-8"?><!--
 ~ Use Extended FAB on Android even if Material Components doesn't support it yet
 ~ See https://github.com/material-components/material-components-android/issues/79
 ~
 ~ Created by Simone Sestito
 -->
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- Change this view with your content -->
    <View
        android:id="@+id/fragmentContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <com.google.android.material.bottomappbar.BottomAppBar
        android:id="@+id/bottomAppBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentBottom="true"
        android:elevation="4dp"
        app:layout_anchor="@+id/fragmentContent"
        app:layout_anchorGravity="bottom|center" />

    <!-- It will NOT work without the style applied -->
    <com.google.android.material.button.MaterialButton
        android:id="@+id/fab"
        style="@style/Widget.MaterialComponents.Button.TextButton.IconButton"
        android:layout_width="wrap_content"
        android:layout_height="64dp"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="24dp"
        android:elevation="6dp"
        android:paddingStart="20dp"
        android:paddingEnd="20dp"
        android:text="@string/fab_text"
        android:textAllCaps="true"
        android:textColor="@android:color/white"
        android:textSize="14sp"
        app:backgroundTint="?attr/colorAccent"
        app:cornerRadius="32dp"
        app:icon="@drawable/ic_fab"
        app:iconPadding="12dp"
        app:iconSize="24dp"
        app:iconTint="@android:color/white"
        app:layout_anchor="@+id/bottomAppBar"
        app:layout_anchorGravity="top|center" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

paddingStart should be "12dp"

The visual height of the fab should be 48dp according to the Material Spec, but given yours is more around 52dp. Setting the total height to 60dp instead of 64dp makes it 48dp.

I think style="@style/Widget.MaterialComponents.Button.TextButton.IconButton"
has changed to
style="@style/Widget.MaterialComponents.Button.TextButton.Icon"