Introducing to XML
XML stands for eXtensible Markup Language and was designed to be a software and hardware independent tool used to transport and store data, with focus on what data is. XML is mostly used for user interface (UI) layouts in Android. Wonder why we need to use XML? XML is easy to parse and manipulate programmatically with a really simple tree-structure.

There are several types of XML file that we should focus on:
Layout XML: we use it to define the actual UI of our application. It’s capable of holding many tools and elements like TextView, Button or even other layouts

Manifest XML: it is used to define all the components of your application. It includes the names of your packages, your classes(Activities), services, receivers and the permissions that your application needs. We’ll talk about this XML later.

String XML: we use it to hard-coded, long string with a single substitute string. For instance, “Hello world” can be replaced by “Hw” if you define it in this XML.

Style XML: This XML is used to different styles and looks for the UI, like color for a specific element of your application.

Drawable XML: it is used to provide abundant of graphics for your application.
At first, we will only concentrate on one type of XML file, Layout XML, as I assume this is the most fundamental XML of our applications.
Now you can try to re-code the sample XML layout below (copy would not work) or copy my code from Github to this awesome XML visualizer from Udacity:
<LinearLayout android:layout_width=”match_parent”
android:layout_height=”match_parent”>
<TextView
android:layout_width=”match_parent”
android:layout_height=”wrap_content”
android:text=”Hello world”
/>
</LinearLayout>
Awesome, you just created your first layout :D .
