Android Canvas

ViewGroup is a collection of Views(TextView, EditText, ListView, etc..), somewhat like a container . A View object is a component of the user interface (UI) like a button or a text box, and it’s also called a widget.

The Android UI model is inherently customizable , offering the means of Android customization, testing, and the ability to create custom UI components in various ways: Inherit an existing component (i.e. TextView , ImageView , etc.), and add/override needed functionality.

A well-designed custom view is much like any other well-designed class. It encapsulates a specific set of functionality with an easy to use interface, it uses CPU and memory efficiently, and so on . In addition to being a well-designed class, though, a custom view should: Conform to Android standards.