使用数据

Question

我在此处遵循此API指南：http://developer.android.com/guide/topics/ui/declaring-layout.html#AdapterViews

这是以上链接的代码段：

String[] fromColumns = {ContactsContract.Data.DISPLAY_NAME,
                        ContactsContract.CommonDataKinds.Phone.NUMBER};
int[] toViews = {R.id.display_name, R.id.phone_number};

我的问题是..在布局上是什么是R.id.display_name和R.id.phone_number？如何在布局.xml中定义它？这与listView容器有什么关系？

另外，R.layout.person_name_and_number如何定义如下所示？

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
        R.layout.person_name_and_number, cursor, fromColumns, toViews, 0);
ListView listView = getListView();
listView.setAdapter(adapter);

感谢。

Answer 1

根据记录的构造函数源代码

SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags)

/**
 * Standard constructor.
 * 
 * @param context The context where the ListView associated with this
 *            SimpleListItemFactory is running
 * @param layout resource identifier of a layout file that defines the views
 *            for this list item. The layout file should include at least
 *            those named views defined in "toViews"
 * @param c The database cursor.  Can be null if the cursor is not available yet.
 * @param from A list of column names representing the data to bind to the UI.  Can be null 
 *            if the cursor is not available yet.
 * @param toViews that should display column in the "from" parameter.
 *            These should all be TextViews. The first N views in this list
 *            are given the values of the first N columns in the from
 *            parameter.  Can be null if the cursor is not available yet.
 * @param flags Flags used to determine the behavior of the adapter,
 * as per {@link CursorAdapter#CursorAdapter(Context, Cursor, int)}.
 */

因此，您的布局person_name_and_number.xml应包含2个TextViews .. ID为R.id.display_name, R.id.phone_number，如下所示

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >
    <TextView
        android:id="@+id/display_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="28dip" />
       <TextView
        android:id="@+id/phone_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="28dip" />
</LinearLayout>

您的列表布局my_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" >
    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />
</LinearLayout> 

因此，您的活动可以定义如下

                public class MyListActivity extends ListActivity {

                      @Override
                      public void onCreate(Bundle savedInstance) {
                            setContentView(R.layout.my_layout);


                     String[] columnsForCursor = new String[] {
    ContactsContract.Data._id, ContactsContract.Data.DISPLAY_NAME,
ContactsContract.CommonDataKinds.Phone.NUMBER };

                            Cursor cursor = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI,columnsForCursor, null, null, null);
                   int[] toViews = new int[] { R.id.display_name, R.id.phone_number };

                   String[] columnsForView = new String[]{ ContactsContract.Data.DISPLAY_NAME,ContactsContract.CommonDataKinds.Phone.NUMBER 
};
                            SimpleCursorAdapter mAdapter = new SimpleCursorAdapter(this, R.layout.list_example_entry, cursor, columnsForView, toViews);

                            ListView listView = getListView();

                            setListAdapter(mAdapter);
                      }
                }

没有必要从ListActivity扩展您的活动。您可以按如下方式初始化布局中定义的ListView对象

            public class MyActivity extends Activity {

                 ListView mListView;
                 SimpleCursorAdapter mAdapter;
                  @Override
                  public void onCreate(Bundle savedInstance) {
                        setContentView(R.layout.my_layout);

                 String[] columnsForCursor = new String[] {
ContactsContract.Data._id, ContactsContract.Data.DISPLAY_NAME,                 ContactsContract.CommonDataKinds.Phone.NUMBER };
                        Cursor cursor = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI, columnsForCursor, null, null, null);

                        int[] toViews = new int[] { R.id.display_name, R.id.phone_number };

                      String[] columnsForView = new String[]{ ContactsContract.Data.DISPLAY_NAME,ContactsContract.CommonDataKinds.Phone.NUMBER };
                        mAdapter = new SimpleCursorAdapter(this,   R.layout.list_example_entry, cursor, columns, toViews);

                        mListView = (ListView) findViewById(R.id.my_listView);
                        mListView.setListAdapter(mAdapter);
                  } // On Create
            } // MyActivity

更新：为了重现上述代码示例，您的应用必须具有READ_CONTACTS权限。要请求此操作，请将此元素作为<manifest>

的子元素添加到清单文件中

<uses-permission android:name="android.permission.READ_CONTACTS" />