AsyncQueryHandler：
官方解释是一个异步帮助类(A helper class to help make handling asynchronous ContentResolver queries
easier.) 。这个类的主要作用就是异步对DB数据库进行操作，加快其数据处理的速度（这个非常重要，特别是大容量的数据处理时，例如几千联系人的数据读取，按正常的处理速度会非常的慢，使用AsyncQueryHandler，这就会大大的加快速度，增加用户的良好体验）。
AsyncQueryHandler重要的方法：
|
final void |
startDelete(int token, Object cookie, Uri uri, String selection, String[] selectionArgs)
This method begins an asynchronous delete.
|
|
final void |
startInsert(int token, Object cookie, Uri uri, ContentValues initialValues)
This method begins an asynchronous insert.
|
|
void |
startQuery(int token, Object cookie, Uri uri, String[] projection, String selection, String[] selectionArgs, String orderBy)
This method begins an asynchronous query.
|
|
final void |
startUpdate(int token, Object cookie, Uri uri, ContentValues values, String selection, String[] selectionArgs)
This method begins an asynchronous update.
|
显然，从方法的名字，我们可以看出，这是使用异步方式对DB数据库进行基本的增，删，改，查。
|
void |
onDeleteComplete(int token, Object cookie, int result)
Called when an asynchronous delete is completed.
|
|
void |
onInsertComplete(int token, Object cookie, Uri uri)
Called when an asynchronous insert is completed.
|
|
void |
onQueryComplete(int token, Object cookie, Cursor cursor)
Called when an asynchronous query is completed.
|
|
void |
onUpdateComplete(int token, Object cookie, int result)
Called when an asynchronous update is completed.
|
这几个方法，分别对应于上面四个异步操作时的回调方法。
AsyncQueryHandler的一个应用：读取电话联系人的数据信息
-
public class TestAsyncQueryHandler extends Activity {
-
-
private static final String NAME = "name", NUMBER = "number", SORT_KEY = "sort_key";
-
-
private List<ContentValues> listData;
-
private AsyncQueryHandler asyncQuery;
-
-
private ListView personList;
-
private BaseAdapter adapter;
-
-
@Override
-
public void onCreate(Bundle savedInstanceState) {
-
super.onCreate(savedInstanceState);
-
-
setContentView(R.layout.main);
-
-
personList = (ListView) findViewById(R.id.list_view);
-
asyncQuery = new MyAsyncQueryHandler(getContentResolver());
-
-
asyncQueryContact();
-
}
-
-
-
private void asyncQueryContact() {
-
-
Uri uri = Uri.parse("content://com.android.contacts/data/phones");
-
String[] projection = { "_id", "display_name", "data1", "sort_key" };
-
asyncQuery.startQuery(0, null, uri, projection, null, null,"sort_key COLLATE LOCALIZED asc");
-
}
-
-
-
private class MyAsyncQueryHandler extends AsyncQueryHandler {
-
-
public MyAsyncQueryHandler(ContentResolver cr) {
-
super(cr);
-
-
}
-
-
@Override
-
protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
-
if (cursor != null && cursor.getCount() > 0) {
-
listData = new ArrayList<ContentValues>();
-
-
for (int i = 0; i < cursor.getCount(); i++) {
-
ContentValues cv = new ContentValues();
-
cursor.moveToPosition(i);
-
String name = cursor.getString(1);
-
String number = cursor.getString(2);
-
String sortKey = cursor.getString(3);
-
if (number.startsWith("+86")) {
-
cv.put(NAME, name);
-
-
cv.put(NUMBER, number.substring(3));
-
cv.put(SORT_KEY, sortKey);
-
} else {
-
cv.put(NAME, name);
-
cv.put(NUMBER, number);
-
cv.put(SORT_KEY, sortKey);
-
}
-
listData.add(cv);
-
}
-
if (listData.size() > 0) {
-
setAdapter(listData);
-
}
-
cursor.close();
-
}
-
}
-
-
}
-
-
private void setAdapter(List<ContentValues> listData) {
-
adapter = new ListAdapter(this, listData);
-
personList.setAdapter(adapter);
-
-
}
-
-
-
private class ListAdapter extends BaseAdapter {
-
-
private LayoutInflater inflater;
-
private List<ContentValues> list;
-
-
public ListAdapter(Context context, List<ContentValues> list) {
-
this.inflater = LayoutInflater.from(context);
-
this.list = list;
-
}
-
-
@Override
-
public int getCount() {
-
return list.size();
-
}
-
-
@Override
-
public Object getItem(int position) {
-
return list.get(position);
-
}
-
-
@Override
-
public long getItemId(int position) {
-
return position;
-
}
-
-
@Override
-
public View getView(int position, View convertView, ViewGroup parent) {
-
ViewHolder holder;
-
if (convertView == null) {
-
convertView = inflater.inflate(R.layout.list_item, null);
-
holder = new ViewHolder();
-
holder.name = (TextView) convertView.findViewById(R.id.name);
-
holder.number = (TextView) convertView.findViewById(R.id.number);
-
convertView.setTag(holder);
-
} else {
-
holder = (ViewHolder) convertView.getTag();
-
}
-
-
ContentValues cv = list.get(position);
-
holder.name.setText(cv.getAsString(NAME));
-
holder.number.setText(cv.getAsString(NUMBER));
-
-
return convertView;
-
}
-
-
private class ViewHolder {
-
TextView name;
-
TextView number;
-
}
-
-
}
-
-
}
这个例子，只是使用了AsyncQueryHandler类中的异步查询方法，其它的方法，也是类似，大家可以自己尝试。
源代码下载地址：
http://download.csdn.net/detail/hfreeman2011/5040647
参考资料：
1.android异步的几种方式
http://ericchan2012.iteye.com/blog/1673929
2.官方文档
http://developer.android.com/reference/android/content/AsyncQueryHandler.html
3.android快速滑动列表 首字母提示
http://download.csdn.net/detail/j1582830/4010012
Android 异步开发之 AsyncQueryHandler
