然而,现在我想能够从数据库中读取数据。我正在使用一个带有 cursorloader 的 listview Fragment,但我无法让信息正确显示。我想在列表视图中列出第一个表中所有群组的名称。
我的问题是,在我最初使用 cursorloader 列出我的联系人时,我使用了 content provider 中 onCreateLoader 方法中的 Uri。具体来说,我使用了 ContactsContracts.Contacts 类中的 CONTENT_URI。
具有 contentprovider 的 cursorloader 示例:
@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
Uri contentUri = ContactsContract.Contacts.CONTENT_URI;
return new CursorLoader(getActivity(),contentUri,PROJECTION,SELECTION,ARGS,ORDER);
}
然而,如果不使用内容提供程序,我不知道在onCreateLoader
方法中该放什么,因为return new CursorLoader(...)
需要第二个参数中的Uri
。
有没有建议可以让我如何在列表视图中显示数据库数据?
片段类代码:
public class GroupListFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> {
CursorAdapter mAdapter;
private OnItemSelectedListener listener;
private static final String[] PROJECTION ={GroupContract.GroupDetails.COLUMN_NAME_GROUP_NAME};
private static final String SELECTION = null;
final String[] FROM = {GroupContract.GroupDetails.COLUMN_NAME_GROUP_NAME};
final int[] TO = {android.R.id.text1};
private static final String[] ARGS = null;
private static final String ORDER = null;
private Cursor c;
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
mAdapter = new SimpleCursorAdapter(getActivity(), android.R.layout.simple_list_item_1,null,FROM,TO,0 );
ReadDBAsync readDB = new ReadDBAsync();
readDB.execute();
}
@Override
public void onActivityCreated(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
setListAdapter(mAdapter);
getLoaderManager().initLoader(0,null,this);
}
@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
Uri contenturi = Uri.parse("content://preamble.oneapp");
Uri tableuri = Uri.withAppendedPath(contenturi,GroupContract.GroupDetails.TABLE_NAME);
return new CursorLoader(getActivity(),tableuri,PROJECTION,SELECTION,ARGS,ORDER);
}
@Override
public void onLoadFinished(Loader<Cursor> cursorLoader, Cursor cursor) {
mAdapter.swapCursor(cursor);
}
@Override
public void onLoaderReset(Loader<Cursor> cursorLoader) {
mAdapter.swapCursor(null);
}
private class ReadDBAsync extends AsyncTask<Void,Void,String> {
@Override
protected String doInBackground(Void... voids) {
ContractDBHelpers mDBHelper = new ContractDBHelpers(getActivity());
SQLiteDatabase db = mDBHelper.getReadableDatabase();
String returnvalue = "database read";
c = db.query(GroupContract.GroupDetails.TABLE_NAME,PROJECTION,null,null,null,null,null);
return returnvalue;
}
@Override
protected void onPostExecute(String result){
Toast.makeText(getActivity(), result, Toast.LENGTH_LONG).show();
}
}
}