SimpleCursorTreeAdapter and CursorLoader for ExpandableListView
android, android-cursorloader, expandablelistadapter, simplecursoradapter
Solution
So i figured out that I needed to map loaderids to groupPositions and this solved my issue:
Here is my `Fragment` class which implements the `CursorLoader`
public class GroupsListFragment extends ExpandableListFragment implements
LoaderManager.LoaderCallbacks<Cursor> {
private final String DEBUG_TAG = getClass().getSimpleName().toString();
private static final String[] CONTACTS_PROJECTION = new String[] {
ContactsContract.Contacts._ID,
ContactsContract.Contacts.DISPLAY_NAME };
private static final String[] GROUPS_PROJECTION = new String[] {
ContactsContract.Groups.TITLE, ContactsContract.Groups._ID };
GroupsAdapter mAdapter;
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
populateContactList();
// Prepare the loader. Either re-connect with an existing one,
// or start a new one.
Loader loader = getLoaderManager().getLoader(-1);
if (loader != null && !loader.isReset()) {
getLoaderManager().restartLoader(-1, null, this);
} else {
getLoaderManager().initLoader(-1, null, this);
}
}
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
// This is called when a new Loader needs to be created.
Log.d(DEBUG_TAG, "onCreateLoader for loader_id " + id);
CursorLoader cl;
if (id != -1) {
// child cursor
Uri contactsUri = ContactsContract.Data.CONTENT_URI;
String selection = "((" + ContactsContract.Contacts.DISPLAY_NAME
+ " NOTNULL) AND ("
+ ContactsContract.Contacts.HAS_PHONE_NUMBER + "=1) AND ("
+ ContactsContract.Contacts.DISPLAY_NAME + " != '') AND ("
+ ContactsContract.CommonDataKinds.GroupMembership.GROUP_ROW_ID
+ " = ? ))";
String sortOrder = ContactsContract.Contacts.DISPLAY_NAME
+ " COLLATE LOCALIZED ASC";
String[] selectionArgs = new String[] { String.valueOf(id) };
cl = new CursorLoader(getActivity(), contactsUri,
CONTACTS_PROJECTION, selection, selectionArgs, sortOrder);
} else {
// group cursor
Uri groupsUri = ContactsContract.Groups.CONTENT_URI;
String selection = "((" + ContactsContract.Groups.TITLE
+ " NOTNULL) AND (" + ContactsContract.Groups.TITLE
+ " != '' ))";
String sortOrder = ContactsContract.Groups.TITLE
+ " COLLATE LOCALIZED ASC";
cl = new CursorLoader(getActivity(), groupsUri,
GROUPS_PROJECTION, selection, null, sortOrder);
}
return cl;
}
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
// Swap the new cursor in.
int id = loader.getId();
Log.d(DEBUG_TAG, "onLoadFinished() for loader_id " + id);
if (id != -1) {
// child cursor
if (!data.isClosed()) {
Log.d(DEBUG_TAG, "data.getCount() " + data.getCount());
HashMap<Integer,Integer> groupMap = mAdapter.getGroupMap();
try {
int groupPos = groupMap.get(id);
Log.d(DEBUG_TAG, "onLoadFinished() for groupPos " + groupPos);
mAdapter.setChildrenCursor(groupPos, data);
} catch (NullPointerException e) {
Log.w("DEBUG","Adapter expired, try again on the next query: "
+ e.getMessage());
}
}
} else {
mAdapter.setGroupCursor(data);
}
}
public void onLoaderReset(Loader<Cursor> loader) {
// This is called when the last Cursor provided to onLoadFinished()
// is about to be closed.
int id = loader.getId();
Log.d(DEBUG_TAG, "onLoaderReset() for loader_id " + id);
if (id != -1) {
// child cursor
try {
mAdapter.setChildrenCursor(id, null);
} catch (NullPointerException e) {
Log.w("TAG", "Adapter expired, try again on the next query: "
+ e.getMessage());
}
} else {
mAdapter.setGroupCursor(null);
}
}
/**
* Populate the contact list
*/
private void populateContactList() {
// Set up our adapter
mAdapter = new GroupsAdapter(getActivity(),this,
android.R.layout.simple_expandable_list_item_1,
android.R.layout.simple_expandable_list_item_1,
new String[] { ContactsContract.Groups.TITLE }, // Name for group layouts
new int[] { android.R.id.text1 },
new String[] { ContactsContract.Contacts.DISPLAY_NAME }, // Name for child layouts
new int[] { android.R.id.text1 });
setListAdapter(mAdapter);
}
}
And here is my adapter which subclasses `SimpleCursorTreeAdapter`
public class GroupsAdapter extends SimpleCursorTreeAdapter {
private final String DEBUG_TAG = getClass().getSimpleName().toString();
private ContactManager mActivity;
private GroupsListFragment mFragment;
protected final HashMap<Integer, Integer> mGroupMap;
// Note that the constructor does not take a Cursor. This is done to avoid
// querying the database on the main thread.
public GroupsAdapter(Context context, GroupsListFragment glf,
int groupLayout, int childLayout, String[] groupFrom,
int[] groupTo, String[] childrenFrom, int[] childrenTo) {
super(context, null, groupLayout, groupFrom, groupTo, childLayout,
childrenFrom, childrenTo);
mActivity = (ContactManager) context;
mFragment = glf;
mGroupMap = new HashMap<Integer, Integer>();
}
@Override
protected Cursor getChildrenCursor(Cursor groupCursor) {
// Given the group, we return a cursor for all the children within that group
int groupPos = groupCursor.getPosition();
int groupId = groupCursor.getInt(groupCursor
.getColumnIndex(ContactsContract.Groups._ID));
Log.d(DEBUG_TAG, "getChildrenCursor() for groupPos " + groupPos);
Log.d(DEBUG_TAG, "getChildrenCursor() for groupId " + groupId);
mGroupMap.put(groupId, groupPos);
Loader loader = mActivity.getLoaderManager().getLoader(groupId);
if ( loader != null && !loader.isReset() ) {
mActivity.getLoaderManager().restartLoader(groupId, null, mFragment);
} else {
mActivity.getLoaderManager().initLoader(groupId, null, mFragment);
}
return null;
}
//Accessor method
public HashMap<Integer, Integer> getGroupMap() {
return mGroupMap;
}
}
Problem
I am trying to asynchronously query a provider by using a `CursorLoader` with a `SimpleCursorTreeAdapter` Here is my `Fragment` class which implements the `CursorLoader` ``` public class GroupsListFragment extends ExpandableListFragment implements LoaderManager.LoaderCallbacks<Cursor> { private final String DEBUG_TAG = getClass().getSimpleName().toString(); private static final String[] CONTACTS_PROJECTION = new String[] { ContactsContract.Contacts._ID, ContactsContract.Contacts.DISPLAY_NAME }; private static final String[] GROUPS_SUMMARY_PROJECTION = new String[] { ContactsContract.Groups.TITLE, ContactsContract.Groups._ID, ContactsContract.Groups.SUMMARY_COUNT, ContactsContract.Groups.ACCOUNT_NAME, ContactsContract.Groups.ACCOUNT_TYPE, ContactsContract.Groups.DATA_SET }; GroupsAdapter mAdapter; @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); populateContactList(); getLoaderManager().initLoader(-1, null, this); } public Loader<Cursor> onCreateLoader(int id, Bundle args) { // This is called when a new Loader needs to be created. Log.d(DEBUG_TAG, "onCreateLoader for loader_id " + id); CursorLoader cl; if (id != -1) { // child cursor Uri contactsUri = ContactsContract.Data.CONTENT_URI; String selection = "((" + ContactsContract.CommonDataKinds.GroupMembership.DISPLAY_NAME + " NOTNULL) AND (" + ContactsContract.CommonDataKinds.GroupMembership.HAS_PHONE_NUMBER + "=1) AND (" + ContactsContract.CommonDataKinds.GroupMembership.DISPLAY_NAME + " != '') AND (" + ContactsContract.CommonDataKinds.GroupMembership.GROUP_ROW_ID + " = ? ))"; String sortOrder = ContactsContract.CommonDataKinds.GroupMembership.DISPLAY_NAME + " COLLATE LOCALIZED ASC"; String[] selectionArgs = new String[] { String.valueOf(id) }; cl = new CursorLoader(getActivity(), contactsUri, CONTACTS_PROJECTION, selection, selectionArgs, sortOrder); } else { // group cursor Uri groupsUri = ContactsContract.Groups.CONTENT_SUMMARY_URI; String selection = "((" + ContactsContract.Groups.TITLE + " NOTNULL) AND (" + ContactsContract.Groups.TITLE + " != '' ))"; String sortOrder = ContactsContract.Groups.TITLE + " COLLATE LOCALIZED ASC"; cl = new CursorLoader(getActivity(), groupsUri, GROUPS_SUMMARY_PROJECTION, selection, null, sortOrder); } return cl; } public void onLoadFinished(Loader<Cursor> loader, Cursor data) { // Swap the new cursor in. int id = loader.getId(); Log.d(DEBUG_TAG, "onLoadFinished() for loader_id " + id); if (id != -1) { // child cursor if (!data.isClosed()) { Log.d(DEBUG_TAG, "data.getCount() " + data.getCount()); try { mAdapter.setChildrenCursor(id, data); } catch (NullPointerException e) { Log.w("DEBUG","Adapter expired, try again on the next query: " + e.getMessage()); } } } else { mAdapter.setGroupCursor(data); } } public void onLoaderReset(Loader<Cursor> loader) { // This is called when the last Cursor provided to onLoadFinished() // is about to be closed. int id = loader.getId(); Log.d(DEBUG_TAG, "onLoaderReset() for loader_id " + id); if (id != -1) { // child cursor try { mAdapter.setChildrenCursor(id, null); } catch (NullPointerException e) { Log.w("TAG", "Adapter expired, try again on the next query: " + e.getMessage()); } } else { mAdapter.setGroupCursor(null); } } /** * Populate the contact list */ private void populateContactList() { // Set up our adapter mAdapter = new GroupsAdapter(getActivity(),this, android.R.layout.simple_expandable_list_item_1, android.R.layout.simple_expandable_list_item_1, new String[] { ContactsContract.Groups.TITLE }, // Name for group layouts new int[] { android.R.id.text1 }, new String[] { ContactsContract.Contacts.DISPLAY_NAME }, // Name for child layouts new int[] { android.R.id.text1 }); setListAdapter(mAdapter); } } ``` And here is my adapter which subclasses `SimpleCursorTreeAdapter` ``` public class GroupsAdapter extends SimpleCursorTreeAdapter { private final String DEBUG_TAG = getClass().getSimpleName().toString(); private ContactManager mActivity; private GroupsListFragment mFragment; // Note that the constructor does not take a Cursor. This is done to avoid // querying the database on the main thread. public GroupsAdapter(Context context, GroupsListFragment glf, int groupLayout, int childLayout, String[] groupFrom, int[] groupTo, String[] childrenFrom, int[] childrenTo) { super(context, null, groupLayout, groupFrom, groupTo, childLayout, childrenFrom, childrenTo); mActivity = (ContactManager) context; mFragment = glf; } @Override protected Cursor getChildrenCursor(Cursor groupCursor) { // Given the group, we return a cursor for all the children within that group int groupId = groupCursor.getInt(groupCursor .getColumnIndex(ContactsContract.Groups._ID)); Log.d(DEBUG_TAG, "getChildrenCursor() for groupId " + groupId); Loader loader = mActivity.getLoaderManager().getLoader(groupId); if ( loader != null && loader.isReset() ) { mActivity.getLoaderManager().restartLoader(groupId, null, mFragment); } else { mActivity.getLoaderManager().initLoader(groupId, null, mFragment); } } } ``` The problem is that when i click one of the parent groups one of three things happens in what appears to be a inconsistent fashion. 1) Either the group opens up and the children appear below it 2) The group does not open and the `setChildrenCursor()` call throws an `NullPointerException` error which gets caught in the try catch block 3) The group does not open and no error is thrown Here is some debugging output in a scenario in which a group is expanded and showing the children: When all groups are displayed it ouputs: ``` 05-20 10:08:22.765: D/GroupsListFragment(22132): onCreateLoader for loader_id -1 05-20 10:08:23.613: D/GroupsListFragment(22132): onLoadFinished() for loader_id -1 ``` -1 is the loader_id of the group cursor Then if i select one group in particular (let's just call it group A) it outputs: ``` 05-20 23:22:31.140: D/GroupsAdapter(13844): getChildrenCursor() for groupId 67 05-20 23:22:31.140: D/GroupsListFragment(13844): onCreateLoader for loader_id 67 05-20 23:22:31.254: D/GroupsListFragment(13844): onLoadFinished() for loader_id 67 05-20 23:22:31.254: D/GroupsListFragment(13844): data.getCount() 4 05-20 23:22:31.254: W/GroupsListFragment(13844): Adapter expired, try again on the next query: null ``` The group does not expand and the `NullPointerException` is caught. Then if i select another group (let's just call it group B) it outputs: ``` 05-20 23:25:38.089: D/GroupsAdapter(13844): getChildrenCursor() for groupId 3 05-20 23:25:38.089: D/GroupsListFragment(13844): onCreateLoader for loader_id 3 05-20 23:25:38.207: D/GroupsListFragment(13844): onLoadFinished() for loader_id 3 05-20 23:25:38.207: D/GroupsListFragment(13844): data.getCount() 6 ``` This time, the `NullPointerException` is not thrown. And instead of group B expanding, group A is expanded. Can anyone explain the behavior that the `setChildrenCursor()` call is exhibiting? I am thinking there is a problem with how the group/child CursorLoaders are instantiated in `onCreateLoader()`. For the group `CursorLoader` i just want all groups in my phone. The child `CursorLoader` should contain all contacts within a group. Does anyone have any ideas what could be the issue? UPDATE Thanks to @Yam's advice I have now modified the `getChildrenCursor()` method. I am now selecting the groupCursor position not the value of ContactsContract.Groups._ID to pass into the initLoader() call. I also changed the logic to call restartLoader() only when loader is not null and loader isReset is false. ``` protected Cursor getChildrenCursor(Cursor groupCursor) { // Given the group, we return a cursor for all the children within that // group int groupPos = groupCursor.getPosition(); Log.d(DEBUG_TAG, "getChildrenCursor() for groupPos " + groupPos); Loader loader = mActivity.getLoaderManager().getLoader(groupPos); if (loader != null && !loader.isReset()) { mActivity.getLoaderManager().restartLoader(groupPos, null, mFragment); } else { mActivity.getLoaderManager().initLoader(groupPos, null, mFragment); } return null; } ``` This definitely makes more sense and does not exhibit some of the erratic behavior of a group expanding sometimes and not other times. However, there are contacts that are being displayed under a group that they don't belong to. And also some groups that do have contacts in them but it won't show any contacts. So it seems that the `getChildrenCursor()` issues may now be resolved. But now it looks to be an issue of how the CursorLoaders are instantiated in the `onCreateLoader()` method. Is the `CursorLoader` returned in the `onCreateLoader()` method for the child cursor being instantiated improperly? UPDATE So I have identified one of my issues. In the `getChildrenCursor()` method if I pass the groupId into the `initLoader()` method then in the `onCreateLoader()` method, when the `CursorLoader` is created it will get the correct groupid parameter for the query. However, in the `onLoadFinished()` the call to `setChildrenCursor()` is getting passed the loader id for the first parameter not the groupPosition. I'm guessing i have to map loader ids to group positions in some data structure. But i'm not sure if this is the best approach. Does anyone have any suggestions?