Custom xml attributes without attrs.xml file
===

Recently I've faced with adding custom xml parameters to my views in xml layout. I know that I should use attrs.xml file for this purpose, but... I have found, that I can use custom parameters without any attrs.xml file at all. Can somebody explain this ? Is this a bug or is this a valid case ?

here is my custom view:

    public class TestView extends View {

    public TestView(final Context context, final AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public TestView(final Context context, final AttributeSet attrs, final int defStyle) {
        super(context, attrs, defStyle);
        final String scheme = "http://red.com/ui/scheme";
        if (attrs != null) {
            Log.d("TestView", "custom param value: " + attrs.getAttributeValue(scheme, "cutom"));
        }
    }

}

and here is the main layout:

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:red="http://red.com/ui/scheme"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />
    
    <com.red.ui.TestView 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#ffAABBCC"
        red:cutom="customvalue"
        />

     </LinearLayout>

It is a simple scratch project, created by Android wizard.