App Layout

An Android app comprises one or more activities. Each activity represents a single screen that has a user interface. Each screen in our app has controls from different layouts, which define a visual structure of an activity or an app widget. Layouts specify a set of rules to place control elements, such as buttons, input fields, text fields, etc., on a view. Let’s explore various Android views and layouts.

Views and layouts

A View is an object that represents a single UI component, such as a button, text box, or image, while a Layout is a container that holds and organizes multiple views in a particular arrangement.

A Layout organizes multiple views on the screen by defining their relative positions and sizes. An Android layout XML file specifies views and layouts as nested elements, with each Layout containing one or more views. The arrangement and appearance of the views are determined by the properties and attributes specified in the Layout.

The View class

The View class is a basic building block for UI components. A View object takes a rectangular screen area. Its main responsibility is to draw elements and handle events. We can create UI components such as buttons and text fields using the View class. The View is the superclass (base class) of the ViewGroup class, which is a superclass for layouts. The following figure shows some common views and layouts and their relationships.