I'm setting up my app so that people can create groups of their friends. When a group is created, it writes 2 tables to the SQL database. The first table has a group name and a group id. The second table has 2 columns, a group id and a user id. This is working fine.
However, now I want to be able to read from the database. I'm using a listview fragment with a cursorloader
but I'm having trouble getting the information to display. I want to list all the group names from the first table in my list view.
My problem is that, when I first used the cursorloader
to list my contacts, I was using a Uri
from the content provider
in the onCreateLoader
method. Specifically I had CONTENT_URI
from the ContactsContracts.Contacts
class.
Example of cursorloader
with contentprovider
:
@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
Uri contentUri = ContactsContract.Contacts.CONTENT_URI;
return new CursorLoader(getActivity(),contentUri,PROJECTION,SELECTION,ARGS,ORDER);
}
However, without using a content provider, I don't know what to put in the onCreateLoader
method because return new CursorLoader(...)
requires a Uri
in the second argument.
Any suggestion on how I might be able to display my database data in a listview?
fragment class code:
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();
}
}
}
Android Guide suggests to create a ContentProvider
when you want to share your data with other applications. If you don't need this, you can just override method loadInBackgroud()
of the CursorLoader
class. For example write like this in your onCreateLoader
:
return new CursorLoader( YourContext, null, YourProjection, YourSelection, YourSelectionArgs, YourOrder )
{
@Override
public Cursor loadInBackground()
{
// You better know how to get your database.
SQLiteDatabase DB = getReadableDatabase();
// You can use any query that returns a cursor.
return DB.query( YourTableName, getProjection(), getSelection(), getSelectionArgs(), null, null, getSortOrder(), null );
}
};