Head First Android Development, 3rd Edition

Chapter 3. Layouts: Being a layout

We’ve only scratched the surface of using layouts.

So far, you’ve seen how to arrange views in a simple linear layout, but there’s so much more that layouts can do. In this chapter we’ll go a little deeper and show you how layouts really work. You’ll learn how to fine-tune your linear layouts. You’ll discover how to use frame layouts and scroll views. And by the end of the chapter, you’ll learn that even though they might look a little different, all layouts—and the views you add to them—have more in common than you might think.

It all starts with a layout

As you already know, layout files are written in XML, and they let you define what your app looks like.

Each time you write a layout, you need to do three things:

1. Specify the type of layout.

   You tell Android how you want any views (such as buttons and text views) to be arranged by specifying a type of layout. A linear layout, for example, arranges views in a linear column or row, one after another.

   <LinearLayout ...>
   
   </LinearLayout>

2. Specify the views.

   Each layout contains one or more views, which your app uses to display information or interact with the user.

   <Button
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="Click me" />

3. Tell an activity to use the layout.

   You tell Android which activity uses the layout you’ve just defined ...