How do you get "android:" tag values in a Custom View

There seems to be a lot of "similar" questions and answers to this scattered around which all refer to how to get a custom attribute from an AttributeSet. What I haven't been able to find so far is how to get an android: namespace tag:

    <com.custom.view.StatusThumbnail
        android:id="@+id/statusThumbnailContainer"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:layout_weight="1"/>

I would like to pull back the layout_height attribute from this custom component. Unfortunately from what I've read the closest I've got to how to do this is:

public StatusThumbnail(Context context, AttributeSet attrs) {
    super(context, attrs);

    String height = attrs.getAttributeValue("android", "layout_height");

But this returns null.

Surely this isn't a rare thing to try and do?