Introduction

A Fragment is a self-contained component with its own user interface (UI) and life-cycle that can be reused in different parts of an app's UI. (A Fragment can also be used without a UI, in order to retain values across configuration changes, but this lesson does not cover that usage.)

A Fragment can be a static part of the UI of an Activity, which means that the Fragment remains on the screen during the entire life-cycle of the Activity. However, the UI of an Activity may be more effective if it adds or removes the Fragment dynamically while the Activity is running.

Activity vs Fragment Life-Cycle

One example of a dynamic Fragment is the DatePicker object, which is an instance of DialogFragment, a subclass of Fragment. The date picker displays a dialog window floating on top of its Activity window when a user taps a button or an action occurs. The user can click OK or Cancel to close the Fragment.

Benefits of using Fragments

• Reuse a Fragment in more than one Activity

• Add or remove dynamically as needed

• Integrate a mini-UI within an Activity

• Retain data instances after a configuration change

• Represent sections of a layout for different screen sizes

This practical introduces the Fragment class and shows you how to include a Fragment as a static part of a UI, as well as how to use Fragment transactions to add, replace, or remove a Fragment dynamically.

What you'll do

• Create a Fragment to use as a UI element that gives users a "yes" or "no" choice.

• Add interactive elements to the Fragment that enable the user to choose "yes" or "no".

• Include the Fragment for the duration of an Activity.

• Use Fragment transactions to add, replace, and remove a Fragment while an Activity is running.