docs/html/guide/topics/ui/binding.jd

page.title=Binding to Data with AdapterView
parent.title=User Interface
parent.link=index.html
@jd:body

<div id="qv-wrapper">
<div id="qv">
  <h2>In this document</h2>
  <ol>
    <li><a href="#FillingTheLayout">Filling the Layout with Data</a></li>
    <li><a href="#HandlingUserSelections">Handling User Selections</a></li>
  </ol>
  
  <h2>Related tutorials</h2>
  <ol>
    <li><a href="{@docRoot}resources/tutorials/views/hello-spinner.html">Spinner</a></li>
    <li><a href="{@docRoot}resources/tutorials/views/hello-listview.html">List View</a></li>
    <li><a href="{@docRoot}resources/tutorials/views/hello-gridview.html">Grid View</a></li>
  </ol>
</div>
</div>

<p>The {@link android.widget.AdapterView} is a ViewGroup subclass whose child Views are determined by an {@link android.widget.Adapter Adapter} that 
binds to data of some type. AdapterView is useful whenever you need to display stored data (as opposed to resource strings or drawables) in your layout.</p>

<p>{@link android.widget.Gallery Gallery}, {@link android.widget.ListView ListView}, and  {@link android.widget.Spinner Spinner} are examples of AdapterView subclasses that you can use to bind to a specific type of data and display it in a certain way. </p>


<p>AdapterView objects have two main responsibilities: </p>
<ul>
    <li>Filling the layout with data
    </li>
    <li>Handling user selections
    </li>
</ul>


<h2 id="FillingTheLayout">Filling the Layout with Data</h2>
<p>Inserting data into the layout is typically done by binding the AdapterView class to an {@link
android.widget.Adapter}, which retrieves data from an external source (perhaps a list that
the code supplies or query results from the device's database). </p>
<p>The following code sample does the following:</p>
<ol>
  <li>Creates a {@link android.widget.Spinner Spinner} with an existing View and binds it to a new ArrayAdapter
that reads an array of colors from the local resources.</li>
  <li>Creates another Spinner object from a View and binds it to a new SimpleCursorAdapter that will read 
people's names from the device contacts (see {@link android.provider.Contacts.People}).</li>
</ol>

<pre>
// Get a Spinner and bind it to an ArrayAdapter that 
// references a String array.
Spinner s1 = (Spinner) findViewById(R.id.spinner1);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
    this, R.array.colors, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
s1.setAdapter(adapter);

// Load a Spinner and bind it to a data query.
private static String[] PROJECTION = new String[] {
        People._ID, People.NAME
    };

Spinner s2 = (Spinner) findViewById(R.id.spinner2);
Cursor cur = managedQuery(People.CONTENT_URI, PROJECTION, null, null);
     
SimpleCursorAdapter adapter2 = new SimpleCursorAdapter(this,
    android.R.layout.simple_spinner_item, // Use a template
                                          // that displays a
                                          // text view
    cur, // Give the cursor to the list adapter
    new String[] {People.NAME}, // Map the NAME column in the
                                         // people database to...
    new int[] {android.R.id.text1}); // The "text1" view defined in
                                     // the XML template
					 
adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
s2.setAdapter(adapter2);
</pre>

<p>Note that it is necessary to have the People._ID column in projection used with CursorAdapter
or else you will get an exception.</p>

<p>If, during the course of your application's life, you change the underlying data that is read by your Adapter,
you should call {@link android.widget.ArrayAdapter#notifyDataSetChanged()}. This will notify the attached View
that the data has been changed and it should refresh itself.</p>

<h2 id="HandlingUserSelections">Handling User Selections</h2>
<p>You handle the user's selection by setting the class's {@link
android.widget.AdapterView.OnItemClickListener} member to a listener and
catching the selection changes. </p>
<pre>
// Create a message handling object as an anonymous class.
private OnItemClickListener mMessageClickedHandler = new OnItemClickListener() {
    public void onItemClick(AdapterView parent, View v, int position, long id)
    {
        // Display a messagebox.
        Toast.makeText(mContext,"You've got an event",Toast.LENGTH_SHORT).show();
    }
};

// Now hook into our object and set its onItemClickListener member
// to our class handler object.
mHistoryView = (ListView)findViewById(R.id.history);
mHistoryView.setOnItemClickListener(mMessageClickedHandler); 
</pre>

<div class="special">
<p>For more discussion on how to create different AdapterViews, read the following tutorials:
<a href="{@docRoot}resources/tutorials/views/hello-spinner.html">Hello Spinner</a>,
<a href="{@docRoot}resources/tutorials/views/hello-listview.html">Hello ListView</a>, and
<a href="{@docRoot}resources/tutorials/views/hello-gridview.html">Hello GridView</a>.
</div>