AdapterView & Adapters Android Training

By Khaled Anaqwa

AdapterView The AdapterView is a ViewGroup subclass

whose child Views are determined by an Adapter that binds AdapterView object to data of some type.

Typically you are going to use subsclasses of AdapterView class instead of using it directly

Example subclasses of AdapterView class ListView Spinner Gallery

Adapter You can populate an AdapterView such

as ListView or GridView by binding the AdapterView instance to an Adapter, which retrieves data from an external source and creates a View that represents each data entry.

AdapterView & Adapters

So The Adapter provides access to the data

items. The Adapter is also responsible for making

a View for each item in the data set. Types of Adatpers - they implements

ListAdatper interface ArrayAdatper CursorAdatper There are a few more

Adapter Class Hierarchy BaseAdatper abstract class implements

ListAdapter and SpinnerAdatper interfaces

ArrayAdapter and CursorAdapter classes are subclasses of BaseAdapter class

AdapterView Responsibilities Two main responsibilities of AdapterView

Filling the layout with data (with a help from Adapter)

Handling user selections - when a user selects an item, perform some action AdapterView.OnItemClickListener AdapterView.OnItemLongClickListener AdapterView.OnItemSelectedListener

ListActivity Android-provided class specially designed for

displaying a list of items by binding to a data source such as an array or Cursor, and exposes event handlers when the user selects an item.

ListActivity hosts a ListView object that can be bound through an adatper to different data sources, typically either an array or a Cursor holding query results.

setListAdapter(ListAdatper adapter) method automatically creates ListView object from the ListAdapter object

Has a default layout that consists of a single, full-screen list in the center of the screen

Example List of COUNTRIES

Notice that this does not load a layout file for the Activity (which you usually do with setContentView(int)).

setListAdapter(ListAdapter) automatically adds a ListView to fill the entire screen of the ListActivity.

What is the difference between a ListView and a ScrollView ?

Simply ScrollView a host for “static” content

and a ListView a host for “dynamic” content.

Listview ListView is a view group that displays a

list of scrollable items. The list items are automatically inserted to the list using an Adapter that pulls content from a source such as an array or database query and converts each item result into a view that's placed into the list.

Spinner A view that displays one child at a time

and lets the user pick among them. The items in the Spinner come from the

Adapter associated with this view.

Example Choose one of COUNTRIES

In ArrayAdapter Data updates

The ArrayAdapter class allows to remove all elements in its underlying data structure with the clear() method call.

You can then add new elements via the add() method or a Collection via the addAll() method.

You can also directly modify the underlying data structure and call the notifyDataSetChanged() method on the adapter to notify him about the changes in data.