# Introduction A [`Fragment`](http://developer.android.com/guide/components/fragments.html) 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`](https://developer.android.com/reference/android/widget/DatePicker.html) object, which is an instance of [`DialogFragment`](https://developer.android.com/reference/android/support/v4/app/DialogFragment.html), a subclass of [`Fragment`](https://developer.android.com/reference/android/app/Fragment.html). 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`](https://developer.android.com/reference/android/app/Fragment.html) 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. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://kaleb-is-caleb.gitbook.io/infosys/fragments/untitled.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.