ReaderforSelfoss/app/src/main/res/layout/activity_reader.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.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">

    <android.support.v4.widget.NestedScrollView
        android:id="@+id/nestedScrollView"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <ImageView
                android:id="@+id/imageView"
                android:layout_width="0dp"
                android:layout_height="200dp"
                android:scaleType="centerCrop"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                />

            <TextView
                android:id="@+id/source"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginEnd="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginRight="16dp"
                android:layout_marginStart="16dp"
                android:layout_marginTop="8dp"
                android:textAppearance="@style/TextAppearance.AppCompat.Small"
                android:textSize="12sp"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/imageView" />

            <TextView
                android:id="@+id/titleView"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginEnd="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginRight="16dp"
                android:layout_marginStart="16dp"
                android:layout_marginTop="6dp"
                android:textAppearance="@style/TextAppearance.AppCompat.Headline"
                android:textStyle="bold"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/source" />

            <TextView
                android:id="@+id/content"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginEnd="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginRight="16dp"
                android:layout_marginStart="16dp"
                android:layout_marginTop="24dp"
                android:paddingBottom="48dp"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/titleView"/>

            <!--<org.sufficientlysecure.htmltextview.HtmlTextView
                android:id="@+id/content"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginEnd="16dp"
                android:layout_marginLeft="16dp"
                android:layout_marginRight="16dp"
                android:layout_marginStart="16dp"
                android:layout_marginTop="24dp"
                android:paddingBottom="48dp"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/titleView" />-->

        </android.support.constraint.ConstraintLayout>

    </android.support.v4.widget.NestedScrollView>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_gravity="end|bottom|right">

        <com.github.rubensousa.floatingtoolbar.FloatingToolbar
            android:id="@+id/floatingToolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:layout_gravity="bottom"
            app:floatingItemBackground="?attr/colorAccent"
            app:floatingMenu="@menu/reader_toolbar" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_alignParentEnd="true"
            android:layout_alignParentRight="true"
            android:layout_gravity="end|bottom|right"
            android:layout_marginBottom="16dp"
            android:layout_marginEnd="16dp"
            android:layout_marginRight="16dp"
            android:paddingBottom="@dimen/activity_vertical_margin"
            android:paddingTop="@dimen/activity_vertical_margin"
            android:src="@drawable/ic_add"
            app:backgroundTint="?attr/colorAccent"
            app:fabSize="mini"
            app:rippleColor="?attr/colorAccentDark" />
    </FrameLayout>

    <FrameLayout
        android:id="@+id/progressBar"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone"
        android:animateLayoutChanges="true"
        android:alpha="0.8"
        android:background="@color/black"
        android:clickable="false">

        <ProgressBar
            style="?android:attr/progressBarStyleLarge"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:progressTint="?attr/colorAccent" />
    </FrameLayout>

</android.support.design.widget.CoordinatorLayout>