Android学习——AsyncQueryHandler

AsyncQueryHandler定义：A helper class to help make handling asynchronous

ContentResolver

queries easier.异步增删改查（

ContentProvider数据

）的帮助类一般数据量较小时，可以用ContentProvider操作数据库，数据量大时，可能会发生ANR，所以用AsyncQueryHandler来进行异步操作数据库。

//新建一个类

private class BackgroundQueryHandler extends AsyncQueryHandler {

public BackgroundQueryHandler(ContentResolver cr) {
super(cr);

}

@Override
protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
mNotesListAdapter.changeCursor(cursor);
super.onQueryComplete(token, cookie, cursor);
}

}

<pre name="code" class="java">//新建一个对象

mContentResolver = getContentResolver();
mBackgroundQueryHandler = new BackgroundQueryHandler(mContentResolver);

//查询

String selection = NoteColumns.PARENT_ID + "=?";mBackgroundQueryHandler.startQuery(FOLDER_NOTE_LIST_QUERY_TOKEN, null,<span style="white-space:pre">	</span>Notes.CONTENT_NOTE_URI, NoteItemData.PROJECTION, selection,<span style="white-space:pre">	</span>new String[] { String.valueOf(mCurrentFolderId) },<span style="white-space:pre">	</span>NoteColumns.MODIFIED_DATE + " DESC");

//查询结束后操作

@Override<span style="white-space:pre">		</span>protected void onQueryComplete(int token, Object cookie, Cursor cursor) {<span style="white-space:pre">			</span>mNotesListAdapter.changeCursor(cursor);<span style="white-space:pre">			</span>super.onQueryComplete(token, cookie, cursor);<span style="white-space:pre">		</span>}