Signal-Android/res/layout/media_overview_gallery_item.xml

<?xml version="1.0" encoding="utf-8"?>
<org.thoughtcrime.securesms.components.SquareFrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <org.thoughtcrime.securesms.components.ThumbnailView
        android:id="@+id/image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:contentDescription="@string/media_preview_activity__media_content_description"
        android:padding="2dp" />

    <TextView
        android:id="@+id/image_file_size"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="4dp"
        android:background="@drawable/media_overview_size_pill_background"
        android:gravity="center"
        android:paddingStart="6dp"
        android:paddingEnd="6dp"
        android:textColor="@color/white"
        android:textSize="12sp"
        android:visibility="gone"
        tools:text="1.3 MB"
        tools:visibility="visible" />

    <FrameLayout
        android:id="@+id/selected_indicator"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/MediaOverview_Media_selected_overlay"
        android:visibility="gone"
        tools:showIn="@layout/media_overview_gallery_item"
        tools:visibility="visible">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:layout_marginStart="8dp"
            android:contentDescription="@string/MediaOverviewActivity_Selected_description"
            app:srcCompat="@drawable/ic_check_circle_solid_20" />

    </FrameLayout>

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