Basic CardView

Material Design.

CardView is easy. Here is the completed code:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context=".MainActivity"
    tools:showIn="@layout/activity_main">

    <androidx.cardview.widget.CardView
        android:layout_width="300dp"
        android:layout_height="200dp"
        android:layout_margin="16dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

CardView can be used with the androidx namespace. Additionally, it uses elevation to automatically lay out the box. Other Views can go inside of it, or you can use ConstraintLayout to position elements at the same root level. Or you can nest TextViews, for example.

    <androidx.cardview.widget.CardView
        android:id="@+id/cardView"
        android:layout_width="300dp"
        android:layout_height="200dp"
        android:layout_margin="16dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="16dp"
            android:text="Welcome!"
            app:layout_constraintStart_toStartOf="@id/cardView"
            app:layout_constraintTop_toTopOf="@id/cardView" />

    </androidx.cardview.widget.CardView>