core/java/android/app/ListFragment.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.app;

import android.os.Bundle;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;

/**
 * An fragment that displays 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.
 * <p>
 * ListActivity hosts a {@link android.widget.ListView ListView} object that can
 * be bound to different data sources, typically either an array or a Cursor
 * holding query results. Binding, screen layout, and row layout are discussed
 * in the following sections.
 * <p>
 * <strong>Screen Layout</strong>
 * </p>
 * <p>
 * ListActivity has a default layout that consists of a single list view.
 * However, if you desire, you can customize the fragment layout by returning
 * your own view hierarchy from {@link #onCreateView}.
 * To do this, your view hierarchy MUST contain a ListView object with the
 * id "@android:id/list" (or {@link android.R.id#list} if it's in code)
 * <p>
 * Optionally, your view hierarchy can contain another view object of any type to
 * display when the list view is empty. This "empty list" notifier must have an
 * id "android:empty". Note that when an empty view is present, the list view
 * will be hidden when there is no data to display.
 * <p>
 * The following code demonstrates an (ugly) custom lisy layout. It has a list
 * with a green background, and an alternate red "no data" message.
 * </p>
 *
 * <pre>
 * &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
 * &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 *         android:orientation=&quot;vertical&quot;
 *         android:layout_width=&quot;match_parent&quot;
 *         android:layout_height=&quot;match_parent&quot;
 *         android:paddingLeft=&quot;8dp&quot;
 *         android:paddingRight=&quot;8dp&quot;&gt;
 *
 *     &lt;ListView android:id=&quot;@id/android:list&quot;
 *               android:layout_width=&quot;match_parent&quot;
 *               android:layout_height=&quot;match_parent&quot;
 *               android:background=&quot;#00FF00&quot;
 *               android:layout_weight=&quot;1&quot;
 *               android:drawSelectorOnTop=&quot;false&quot;/&gt;
 *
 *     &lt;TextView android:id=&quot;@id/android:empty&quot;
 *               android:layout_width=&quot;match_parent&quot;
 *               android:layout_height=&quot;match_parent&quot;
 *               android:background=&quot;#FF0000&quot;
 *               android:text=&quot;No data&quot;/&gt;
 * &lt;/LinearLayout&gt;
 * </pre>
 *
 * <p>
 * <strong>Row Layout</strong>
 * </p>
 * <p>
 * You can specify the layout of individual rows in the list. You do this by
 * specifying a layout resource in the ListAdapter object hosted by the fragment
 * (the ListAdapter binds the ListView to the data; more on this later).
 * <p>
 * A ListAdapter constructor takes a parameter that specifies a layout resource
 * for each row. It also has two additional parameters that let you specify
 * which data field to associate with which object in the row layout resource.
 * These two parameters are typically parallel arrays.
 * </p>
 * <p>
 * Android provides some standard row layout resources. These are in the
 * {@link android.R.layout} class, and have names such as simple_list_item_1,
 * simple_list_item_2, and two_line_list_item. The following layout XML is the
 * source for the resource two_line_list_item, which displays two data
 * fields,one above the other, for each list row.
 * </p>
 *
 * <pre>
 * &lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
 * &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 *     android:layout_width=&quot;match_parent&quot;
 *     android:layout_height=&quot;wrap_content&quot;
 *     android:orientation=&quot;vertical&quot;&gt;
 *
 *     &lt;TextView android:id=&quot;@+id/text1&quot;
 *         android:textSize=&quot;16sp&quot;
 *         android:textStyle=&quot;bold&quot;
 *         android:layout_width=&quot;match_parent&quot;
 *         android:layout_height=&quot;wrap_content&quot;/&gt;
 *
 *     &lt;TextView android:id=&quot;@+id/text2&quot;
 *         android:textSize=&quot;16sp&quot;
 *         android:layout_width=&quot;match_parent&quot;
 *         android:layout_height=&quot;wrap_content&quot;/&gt;
 * &lt;/LinearLayout&gt;
 * </pre>
 *
 * <p>
 * You must identify the data bound to each TextView object in this layout. The
 * syntax for this is discussed in the next section.
 * </p>
 * <p>
 * <strong>Binding to Data</strong>
 * </p>
 * <p>
 * You bind the ListFragment's ListView object to data using a class that
 * implements the {@link android.widget.ListAdapter ListAdapter} interface.
 * Android provides two standard list adapters:
 * {@link android.widget.SimpleAdapter SimpleAdapter} for static data (Maps),
 * and {@link android.widget.SimpleCursorAdapter SimpleCursorAdapter} for Cursor
 * query results.
 * </p>
 *
 * @see #setListAdapter
 * @see android.widget.ListView
 */
public class ListFragment extends Fragment {
    final private Handler mHandler = new Handler();

    final private Runnable mRequestFocus = new Runnable() {
        public void run() {
            mList.focusableViewAvailable(mList);
        }
    };
    
    final private AdapterView.OnItemClickListener mOnClickListener
            = new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
            onListItemClick((ListView)parent, v, position, id);
        }
    };

    ListAdapter mAdapter;
    ListView mList;

    public ListFragment() {
    }

    /**
     * Provide default implementation to return a simple list view.
     */
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        return inflater.inflate(com.android.internal.R.layout.list_content,
                container, false);
    }

    /**
     * Attach to list view once Fragment is ready to run.
     */
    @Override
    public void onReady(Bundle savedInstanceState) {
        super.onReady(savedInstanceState);
        ensureList();
    }

    /**
     * Detach from list view.
     */
    @Override
    public void onDestroyView() {
        mHandler.removeCallbacks(mRequestFocus);
        mList = null;
        super.onDestroyView();
    }

    /**
     * This method will be called when an item in the list is selected.
     * Subclasses should override. Subclasses can call
     * getListView().getItemAtPosition(position) if they need to access the
     * data associated with the selected item.
     *
     * @param l The ListView where the click happened
     * @param v The view that was clicked within the ListView
     * @param position The position of the view in the list
     * @param id The row id of the item that was clicked
     */
    public void onListItemClick(ListView l, View v, int position, long id) {
    }

    /**
     * Provide the cursor for the list view.
     */
    public void setListAdapter(ListAdapter adapter) {
        mAdapter = adapter;
        if (mList != null) {
            mList.setAdapter(adapter);
        }
    }

    /**
     * Set the currently selected list item to the specified
     * position with the adapter's data
     *
     * @param position
     */
    public void setSelection(int position) {
        ensureList();
        mList.setSelection(position);
    }

    /**
     * Get the position of the currently selected list item.
     */
    public int getSelectedItemPosition() {
        ensureList();
        return mList.getSelectedItemPosition();
    }

    /**
     * Get the cursor row ID of the currently selected list item.
     */
    public long getSelectedItemId() {
        ensureList();
        return mList.getSelectedItemId();
    }

    /**
     * Get the activity's list view widget.
     */
    public ListView getListView() {
        ensureList();
        return mList;
    }

    /**
     * Get the ListAdapter associated with this activity's ListView.
     */
    public ListAdapter getListAdapter() {
        return mAdapter;
    }

    private void ensureList() {
        if (mList != null) {
            return;
        }
        View root = getView();
        if (root == null) {
            throw new IllegalStateException("Content view not yet created");
        }
        View emptyView = root.findViewById(com.android.internal.R.id.empty);
        mList = (ListView)root.findViewById(com.android.internal.R.id.list);
        if (mList == null) {
            throw new RuntimeException(
                    "Your content must have a ListView whose id attribute is " +
                    "'android.R.id.list'");
        }
        if (emptyView != null) {
            mList.setEmptyView(emptyView);
        }
        mList.setOnItemClickListener(mOnClickListener);
        if (mAdapter != null) {
            setListAdapter(mAdapter);
        }
        mHandler.post(mRequestFocus);
    }
}