Basic documentation for custom drawables

 *     whose overall size is modified based on the current level.

 * </ul>

 *

 * <a name="Custom"></a>

 * <h3>Custom drawables</h3>

 *

 * <p>

 * All versions of Android allow the Drawable class to be extended and used at

 * run time in place of framework-provided drawable classes. Starting in

 * {@link android.os.Build.VERSION_CODES#N API 24}, custom drawables classes

 * may also be used in XML.

 * <p>

 * <strong>Note:</strong> Custom drawable classes are only accessible from

 * within your application package. Other applications will not be able to load

 * them.

 * <p>

 * At a minimum, custom drawable classes must implement the abstract methods on

 * Drawable and should override the {@link Drawable#draw(Canvas)} method to

 * draw content.

 * <p>

 * Custom drawables classes may be used in XML in multiple ways:

 * <ul>

 *     <li>

 *         Using the fully-qualified class name as the XML element name. For

 *         this method, the custom drawable class must be a public top-level

 *         class.

 * <pre>

 * <com.myapp.MyCustomDrawable xmlns:android="http://schemas.android.com/apk/res/android"

 *     android:color="#ffff0000" />

 * </pre>

 *     </li>

 *     <li>

 *         Using <em>drawable</em> as the XML element name and specifying the

 *         fully-qualified class name from the <em>class</em> attribute. This

 *         method may be used for both public top-level classes and public

 *         static inner classes.

 * <pre>

 * <drawable xmlns:android="http://schemas.android.com/apk/res/android"

 *     class="com.myapp.MyTopLevelClass$InnerCustomDrawable"

 *     android:color="#ffff0000" />

 * </pre>

 *     </li>

 * </ul>

 *

 * <div class="special reference">

 * <h3>Developer Guides</h3>

 * <p>For more information about how to use drawables, read the