A LinearLayout
must have the attribute android:orientation
as follows:
<LinearLayout
android:id="@+id/top_action_bar"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="top" >
This attribute provides the direction of the children views, see:
vertical (a row)
<LinearLayout>
[View 1]
[View 2]
[View 3]
</LinearLayout>
horizontal (a column)
<LinearLayout> [View 1] [View 2] [View 3] </LinearLayout>