UI Styles

Introduction
- A style is a collection of properties that specify the look and format of a UI element. A style can specify properties such as height, padding, font color, font size, background color, and much more.
- A style is defined in an XML resource that is separate from the XML that specifies the layout.
- Styles are normally kept in the styles.xml file in the res/values directory.
- Example
```
<resources>
    <style name="CodeFont">
        <item name="android:layout_width">match_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textColor">#00FF00</item>
        <item name="android:typeface">monospace</item>
    </style>
</resources>
```
  which can then be used in a layout, e.g., ...
```
<TextView
    style="@style/CodeFont"
    android:text="@string/hello"
</TextView>
```
Inheritance
- Styles can inherit from, and override aspects of, standard Android styles and users' styles.
- To inherit from a standard Android style, use the parent tag, e.g.,
```
<style name="GreenText" 
    parent="@android:style/TextAppearance">
    <item name="android:textColor">#00FF00</item>
</style>
```
  inherits from the standard Android text style, but sets the font to be green.
- To inherit from an existing style, extend the style name with a "." separateor, e.g.,
```
<style name="CodeFont.BigRed">
    <item name="android:textSize">60sp</item>
    <item name="android:textColor">#FF0000</item>
</style>
```
Example
MainActivity.java
activity_main.xml
styles.xml
strings.xml
dimens.xml