session-android/res/layout/media_preview_activity.xml

<?xml version="1.0" encoding="utf-8"?>

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/default_session_background">

    <org.thoughtcrime.securesms.components.viewpager.HackyViewPager
        android:id="@+id/media_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clickable="true"/>

    <LinearLayout
        android:id="@+id/media_preview_details_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:orientation="vertical"
        android:background="@drawable/image_shade"
        android:gravity="bottom"
        android:visibility="gone"
        android:animateLayoutChanges="true">

        <org.thoughtcrime.securesms.components.MaxHeightScrollView
            android:id="@+id/media_preview_caption_container"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingTop="32dp"
            android:animateLayoutChanges="true"
            app:scrollView_maxHeight="120dp">

            <org.thoughtcrime.securesms.components.emoji.EmojiTextView
                android:id="@+id/media_preview_caption"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:paddingStart="16dp"
                android:paddingEnd="16dp"
                android:paddingBottom="8dp"
                style="@style/Signal.Text.Body"
                android:textColor="@color/core_white"
                android:gravity="bottom"
                tools:text="With great power comes great responsibility." />

        </org.thoughtcrime.securesms.components.MaxHeightScrollView>

        <android.support.v7.widget.RecyclerView
            android:id="@+id/media_preview_album_rail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:layout_marginStart="12dp"
            android:layout_marginEnd="12dp"
            tools:layout_height="64dp"/>

        <FrameLayout
            android:id="@+id/media_preview_playback_controls_container"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:animateLayoutChanges="true"/>

    </LinearLayout>

</FrameLayout>