A layout is the visual component of a user interface in Android. The layout is not a class but rather an XML file that is used to tell the operating system what visual objects are to be displayed, how those objects are configured, and where those objects should be displayed on the screen. The XML in the file does use objects. The objects that make up an Android interface are referred to as widgets. Widgets are subclasses of the
View class. Android widgets include widgets to define where other widgets are displayed (for example,
RelativeLayout), to directly interact with the user (for example,
RadioButton), and to provide some type of navigation within the interfaces (for example,
ScrollView). Developing an understanding of the layout XML ...