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

<?xml version="1.0" encoding="utf-8"?>
<eu.kanade.tachiyomi.ui.reader.viewer.pager.PageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical|center_horizontal"
        android:id="@+id/progress_container"
        android:orientation="vertical">

        <ProgressBar
            android:id="@+id/progress"
            style="?android:attr/progressBarStyleLarge"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:id="@+id/progress_text"
            android:layout_gravity="center"
            android:visibility="invisible"
            android:textSize="16sp" />

    </LinearLayout>

    <com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
        android:id="@+id/image_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/retry_button"
        android:text="@string/action_retry"
        android:layout_gravity="center"
        android:visibility="gone"/>

</eu.kanade.tachiyomi.ui.reader.viewer.pager.PageView>