CardView: How do I add a gradient background while maintaining the radius

If I may ask, are you per-chance testing/running on a pre-lollipop Android device? Your code seems to work as you desire (curved corners showing with the gradient) except on Android 4.

To achieve the desired result on pre-lollipop devices, you can add <corners android:radius="4dp" /> to your @drawable/btn_gradient file, (you would have to set the corner radius to match the CardView's cardCornerRadius.

<androidx.cardview.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="@dimen/_10sdp"
    app:cardCornerRadius="@dimen/_10sdp"
    app:cardElevation="@dimen/_1sdp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:background="@drawable/gradient_16"
        android:padding="@dimen/_6sdp">

    </LinearLayout>
</androidx.cardview.widget.CardView>

and gradient be like

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:startColor="#5B86E5"
        android:endColor="#36D1DC"
        android:angle="180" />

    <corners
        android:radius="10dp">
    </corners>
</shape>

CardView card_radius and gradient radius should be same dimentions