Estou tentando criar RelativeLayout personalizado dentro do ScrollView.
Agora eu tenho que copiar esta parte do código em todos os lugares onde eu quero usá-lo:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="xxx"
        android:layout_height="yyy">

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="top"
            android:layout_margin="@dimen/card_margin"
            android:background="@drawable/card_background"
            android:gravity="center"
            android:padding="@dimen/card_padding">

        // content
    </RelativeLayout>
</ScrollView>

Eu gostaria de obter os mesmos resultados com apenas isso:

<MyScrollableRelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="xxx"
        android:layout_height="yyy">

    // content
</MyScrollableRelativeLayout>

É possível fazê-lo dessa maneira?

Atualização 1

Eu tentei fazer isso desta maneira:

public class MyScrollableRelativeLayout extends ScrollView {
    private RelativeLayout content;
    int padding;
    int margin;

    public MyScrollableRelativeLayout(Context context) {
        super(context);
        postConstruct();
    }

    public MyScrollableRelativeLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        postConstruct();
    }

    public MyScrollableRelativeLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        postConstruct();
    }

    private void postConstruct() {
        float scale = getResources().getDisplayMetrics().density;
        padding = (int) (5 * scale);
        margin = (int) (20 * scale);

        content = new RelativeLayout(getContext());
        FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
        layoutParams.setMargins(margin, margin, margin, margin);
        addView(content, layoutParams);
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        setLook();
    }

    private void setLook() {
        setCardBackground();
        setCardPadding();
    }

    private void setCardBackground() {
        content.setBackground(getResources().getDrawable(R.drawable.card_background));
    }

    private void setCardPadding() {
        setPadding(padding, padding, padding, padding);
    }

    @Override
    public void addView(@NonNull View child) {
        if (getChildCount() == 0) {
            super.addView(child);
        } else {
            content.addView(child);
        }
    }

    @Override
    public void addView(@NonNull View child, int index) {
        if (getChildCount() == 0) {
            super.addView(child, index);
        } else {
            content.addView(child, index);    }
    }

    @Override
    public void addView(@NonNull View child, ViewGroup.LayoutParams params) {
        if (getChildCount() == 0) {
            super.addView(child, params);
        } else {
            content.addView(child, params);
        }
    }

    @Override
    public void addView(@NonNull View child, int index, ViewGroup.LayoutParams params) {
        if (getChildCount() == 0) {
            super.addView(child, index, params);
        } else {
            content.addView(child, index, params);
        }
    }
}

Mas o problema no elemento dentro do ScrollableCardRelativeLayout está se substituindo. Como se estivessem ignorandoandroid:layout_* atributo. O que estou fazendo errado?