tachiyomi/app/src/main/res/layout/appwidget_loading.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/appwidget_background">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="@string/loading"
        android:textColor="?android:attr/textColorPrimary" />

</FrameLayout>