Referencing custom view in XML doesn´t work both documented ways?

Answer 1

You should use lowercase view in the xml for your custom layout:

<view class="com.test.www.BrushPreview" android:id="@+id/brushview"
    android:layout_width="100dip" android:layout_height="100dip"
    android:layout_gravity="center" />

(according to your link too), and it should work.

Otherwise it tries to create a android.view.View instance.