114 lines
5.0 KiB
Plaintext
114 lines
5.0 KiB
Plaintext
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page.title=Binding to Data with AdapterView
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parent.title=User Interface
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parent.link=index.html
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@jd:body
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<div id="qv-wrapper">
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<div id="qv">
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<h2>In this document</h2>
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<ol>
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<li><a href="#FillingTheLayout">Filling the Layout with Data</a></li>
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<li><a href="#HandlingUserSelections">Handling User Selections</a></li>
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</ol>
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<h2>Related tutorials</h2>
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<ol>
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<li><a href="{@docRoot}resources/tutorials/views/hello-spinner.html">Spinner</a></li>
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<li><a href="{@docRoot}resources/tutorials/views/hello-listview.html">List View</a></li>
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<li><a href="{@docRoot}resources/tutorials/views/hello-gridview.html">Grid View</a></li>
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</ol>
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</div>
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</div>
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<p>The {@link android.widget.AdapterView} is a ViewGroup subclass whose child Views are determined by an {@link android.widget.Adapter Adapter} that
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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>
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<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>
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<p>AdapterView objects have two main responsibilities: </p>
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<ul>
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<li>Filling the layout with data
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</li>
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<li>Handling user selections
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</li>
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</ul>
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<h2 id="FillingTheLayout">Filling the Layout with Data</h2>
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<p>Inserting data into the layout is typically done by binding the AdapterView class to an {@link
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android.widget.Adapter}, which retrieves data from an external source (perhaps a list that
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the code supplies or query results from the device's database). </p>
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<p>The following code sample does the following:</p>
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<ol>
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<li>Creates a {@link android.widget.Spinner Spinner} with an existing View and binds it to a new ArrayAdapter
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that reads an array of colors from the local resources.</li>
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<li>Creates another Spinner object from a View and binds it to a new SimpleCursorAdapter that will read
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people's names from the device contacts (see {@link android.provider.Contacts.People}).</li>
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</ol>
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<pre>
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// Get a Spinner and bind it to an ArrayAdapter that
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// references a String array.
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Spinner s1 = (Spinner) findViewById(R.id.spinner1);
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ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
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this, R.array.colors, android.R.layout.simple_spinner_item);
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adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
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s1.setAdapter(adapter);
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// Load a Spinner and bind it to a data query.
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private static String[] PROJECTION = new String[] {
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People._ID, People.NAME
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};
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Spinner s2 = (Spinner) findViewById(R.id.spinner2);
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Cursor cur = managedQuery(People.CONTENT_URI, PROJECTION, null, null);
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SimpleCursorAdapter adapter2 = new SimpleCursorAdapter(this,
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android.R.layout.simple_spinner_item, // Use a template
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// that displays a
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// text view
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cur, // Give the cursor to the list adapter
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new String[] {People.NAME}, // Map the NAME column in the
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// people database to...
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new int[] {android.R.id.text1}); // The "text1" view defined in
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// the XML template
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adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
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s2.setAdapter(adapter2);
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</pre>
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<p>Note that it is necessary to have the People._ID column in projection used with CursorAdapter
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or else you will get an exception.</p>
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<p>If, during the course of your application's life, you change the underlying data that is read by your Adapter,
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you should call {@link android.widget.ArrayAdapter#notifyDataSetChanged()}. This will notify the attached View
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that the data has been changed and it should refresh itself.</p>
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<h2 id="HandlingUserSelections">Handling User Selections</h2>
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<p>You handle the user's selection by setting the class's {@link
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android.widget.AdapterView.OnItemClickListener} member to a listener and
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catching the selection changes. </p>
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<pre>
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// Create a message handling object as an anonymous class.
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private OnItemClickListener mMessageClickedHandler = new OnItemClickListener() {
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public void onItemClick(AdapterView parent, View v, int position, long id)
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{
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// Display a messagebox.
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Toast.makeText(mContext,"You've got an event",Toast.LENGTH_SHORT).show();
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}
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};
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// Now hook into our object and set its onItemClickListener member
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// to our class handler object.
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mHistoryView = (ListView)findViewById(R.id.history);
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mHistoryView.setOnItemClickListener(mMessageClickedHandler);
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</pre>
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<div class="special">
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<p>For more discussion on how to create different AdapterViews, read the following tutorials:
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<a href="{@docRoot}resources/tutorials/views/hello-spinner.html">Hello Spinner</a>,
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<a href="{@docRoot}resources/tutorials/views/hello-listview.html">Hello ListView</a>, and
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<a href="{@docRoot}resources/tutorials/views/hello-gridview.html">Hello GridView</a>.
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</div>
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