Changes

The user interface design for our activity is stored in a file named activity_android_sample.xml which, in turn, is located under app -> res -> layout in the project file hierarchy. This layout file includes the app bar (also known as an action bar) that appears across the top of the device screen (marked A in Figure 3-8) and the floating action button (the email button marked B). In addition to these items, the activity_android_sample.xml layout file contains a reference to a second file containing the content layout (marked C):

[[Image:android_studio_top_level_layout.png]]