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== Blank vs. Empty Activity Templates ==

As outlined in the chapter entitled The Anatomy of an Android Application, Android applications are made up of one or more activities. An activity is a standalone module of application functionality that usually correlates directly to a single user interface screen. As such, when working with the Android Studio Designer we are invariably working on the layout for an activity.

Figure 15-1

The Blank Activity, on the other hand, consists of two layout files. The top level layout file has a CoordinatorLayout as the root view, a configurable app bar, a menu preconfigured with a single menu item (A in Figure 15 2), a floating action button (B) and a reference to the second layout file in which the layout for the content area of the activity user interface is declared:

Figure 15-3

* '''A – Palette''' – The palette provides access to the range of view components provided by the Android SDK. These are grouped into categories for easy navigation. Items may be added to the layout either by dragging a view component from the palette and dropping it at the desired position on the layout, or by clicking on a widget in the palette and then clicking at the location on the layout where it is to be positioned.

* '''B – Device Screen''' – The device screen provides a visual “what you see is what you get” representation of the user interface layout as it is being designed. This layout allows for direct manipulation of the design in terms of allowing views to be selected, deleted, moved and resized. The device model represented by the layout can be changed at any time using a menu located in the toolbar.

The properties panel provides access to all of the available settings for the currently selected component. Clicking in the panel and typing characters will begin a search process to highlight and select the closest match to the typed characters.

While the properties panel provides access to the full list of properties for the currently selected component, quick access to a subset of common properties can be gained by double clicking on the component view in the layout. Double clicking on a TextView component, for example, provides quick access to the text and id properties for the view as shown in Figure 15-5:

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