activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.cardview.widget.CardView
            android:id="@+id/head"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            app:cardBackgroundColor="@color/skyblue">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center|start"
                android:text="@string/appName"
                android:textColor="@color/white"
                android:textSize="18sp"
                android:textStyle="bold"
                android:layout_marginLeft="10dp"
                android:layout_marginStart="10dp" />

            <ImageButton
                android:id="@+id/menu"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center|end"
                android:layout_marginEnd="10dp"
                android:layout_marginRight="10dp"
                android:background="@android:color/transparent"
                android:src="@drawable/ic_action_menu"
                android:tint="@color/white" />
        </androidx.cardview.widget.CardView>

        <com.androidcodeman.simpleimagegallery.utils.AutoFitRecyclerView
            android:id="@+id/folderRecycler"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@color/white"
            android:columnWidth="@dimen/folder_column_width"
            android:clipToPadding="false"
            android:layout_below="@id/head">
        </com.androidcodeman.simpleimagegallery.utils.AutoFitRecyclerView>

    </RelativeLayout>
    
    <TextView
        android:id="@+id/empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="@string/empty"
        android:textSize="18sp"
        android:textStyle="bold"
        android:visibility="gone" />

</FrameLayout>