Binding to Data with AdapterView

The AdapterView is a ViewGroup subclass whose child Views are determined by an 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.

Gallery, ListView, and 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.

AdapterView objects have two main responsibilities:

• Filling the layout with data
• Handling user selections

레이아웃을 데이터로 채우는 것
사용자가 선택한 것을 처리하는 것

Filling the Layout with Data

Inserting data into the layout is typically done by binding the AdapterView class to an Adapter, which retireves data from an external source (perhaps a list that the code supplies or query results from the device's database).

The following code sample does the following:

1. Creates a Spinner with an existing View and binds it to a new ArrayAdapter that reads an array of colors from the local resources.
2. 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 Contacts.People).

이미 존재하는 뷰를 사용해서 스피너Spinner를 생성하고, 로컬 리소스의 컬러 배열을 읽어들이는 새로운 어레이어댑터ArrayAdapter에 해당 스퍼너를 바인드한다.
또 다른 스피너Spinner 오브젝트를 뷰에서 생성하고, 디바이스의 컨택(Contacts.People를 보라)에서 사람들의 이름을 읽어들이는 새로운 심플커서어댑터SimpleCursorAdapter에 해당 스피너를 바인드한다.

// Get a Spinner and bind it to an ArrayAdapter that 
// references a String array.
Spinner s1 = (Spinner) findViewById(R.id.spinner1);
ArrayAdapter 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 adatper
    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);

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

If, during the course of your application's life, you change the underlying data that is read by your Adapter, you should call notifyDataSetChanged(). This will notify the attached View that the data has been changed and it should refresh itself.

Handling User Selections

You handle the user's selecction by setting the class's AdapterView.OnItemClickListener member to a listener and catching the selection changes.

// 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);