Learning Android™ Application Programming: A Hands-On Guide to Building Android Applications

Creating a Simple User Interface

At this point, your activity_timer activity is using as its base tag the RelativeLayout view group. By using the RelativeLayout class, you’re telling the app to position the views in relation to how other views are positioned. For example, the position of views could be determined by whether the views are to the right or left of another view, below or above another view, centered in the view group, aligned to the left or right of each other, or even aligned to the bottom or top of the view group.

The values for the layout properties are either a Boolean or an ID that references another view. In the XML layout, they can be declared in any order. For example, if android:layout_centerVertical is set to true, then ...