godot/platform/android/java/lib/res/layout/snackbar.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:drawable/dialog_holo_dark_frame"
    android:gravity="center_vertical"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/snackbar_text"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text=""
        android:textColor="@android:color/white"
        android:textSize="14sp"
        android:padding="8dp"/>

    <Button
        android:id="@+id/snackbar_action"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#00FFFFFF"
        android:text="Action"
        android:textColor="#61B7FC"
        android:paddingHorizontal="8dp"/>
</LinearLayout>