Android Api Demos登顶之路（108）View-->ExpanableLists-->Cursor

/*本例演示了为ExpandableListView设置数据适配器的第二种方式：Cursor
*/
public class MainActivity extends ExpandableListActivity {
private static final String[] CONTACTS_PROJECTION = new String[] {
Contacts._ID, Contacts.DISPLAY_NAME };
private static final int GROUP_ID_COLUM_INDEX = 0;

private static final String[] PHONE_NUMBER_PROJECTION = new String[] {
Phone._ID, Phone.NUMBER };

// group的标志
private static final int TOKEN_GROUP = 0;
// child的标志
private static final int TOKEN_CHILD = 1;

// 异步查询类
private class QueryHandler extends AsyncQueryHandler {
private CursorTreeAdapter mAdapter;

// 对未实现的构造函数进行改造，但super的参数是不能变的
public QueryHandler(Context context, CursorTreeAdapter adapter) {
super(context.getContentResolver());
this.mAdapter = adapter;
}

// 重写该方法，根据标志位为Adapter设置Cursor
@Override
protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
switch (token) {
case TOKEN_GROUP:
mAdapter.setGroupCursor(cursor);
break;
case TOKEN_CHILD:
int groupPosition = (Integer) cookie;
mAdapter.setChildrenCursor(groupPosition, cursor);
break;
}
}

}

private QueryHandler mHandler;
private CursorTreeAdapter mAdapter;

private class MyExpandableListAdapter extends SimpleCursorTreeAdapter {

// 注意这里在构造方法中不需要Cursor cursor参数，避免在主线程中对数据库进行查询
public MyExpandableListAdapter(Context context, int groupLayout,
String[] groupFrom, int[] groupTo, int childLayout,
String[] childFrom, int[] childTo) {
super(context, null, groupLayout, groupFrom, groupTo, childLayout,
childFrom, childTo);
// TODO Auto-generated constructor stub
}

@Override
protected Cursor getChildrenCursor(Cursor groupCursor) {
// 构建一个新的Uri的builder，该builder继承此Uri的属性
Uri.Builder builder = Contacts.CONTENT_URI.buildUpon();
ContentUris.appendId(builder,
groupCursor.getLong(GROUP_ID_COLUM_INDEX));
// 添加子项的Uri路径
builder.appendEncodedPath(Contacts.Data.CONTENT_DIRECTORY);
Uri phoneNumberUri = builder.build();

// 查询子项数据,由handler负责查询，所次需要返回cursor结果集
mHandler.startQuery(TOKEN_CHILD, groupCursor.getPosition(),
phoneNumberUri, PHONE_NUMBER_PROJECTION, Phone.MIMETYPE
+ "=?", new String[] { Phone.CONTENT_ITEM_TYPE },
null);
return null;
}

}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

mAdapter = new MyExpandableListAdapter(
this,
// 该布局中只有一个textView
android.R.layout.simple_expandable_list_item_1,
new String[] { Contacts.DISPLAY_NAME },
new int[] { android.R.id.text1 },
android.R.layout.simple_expandable_list_item_1,
new String[] { Phone.NUMBER }, new int[] { android.R.id.text1 });
setListAdapter(mAdapter);
mHandler = new QueryHandler(this, mAdapter);

// 查询父项
mHandler.startQuery(TOKEN_GROUP, null, Contacts.CONTENT_URI,
CONTACTS_PROJECTION, Contacts.HAS_PHONE_NUMBER+"=1", null, null);
}

@Override
protected void onDestroy() {
super.onDestroy();
mAdapter.changeCursor(null);
mAdapter=null;
}
}