Removing rows from an Android SQLite Cursor

I query and get a result set back, but I need to do some calculations that are impossible in the SQLite WHERE clause in order to determine what shows up in the ListView. How can I remove certain rows fro开发者_如何学Pythonm the cursor? I know it is the same question as this Filter rows from Cursor so they don't show up in ListView but that answer does not help. Can an example be provided if there isn't a simpler way to do this?

It might work to simply retain all the rows in the Cursor, but then use a custom adapter to hide the unwanted rows at display time. For example, if you extend CursorAdapter, then you might have something like this in your bindView implementation:

View v = view.findViewById(R.id.my_list_entry);
boolean keepThisRow = .......; // do my calculations
v.setVisibility(keepThisRow ? View.VISIBLE : View.GONE);

There should be a better way to do this, but what I ended up doing is storing the ID of each row I wanted in a string ArrayList, and then requerying where _id IN arraListOfIds.toString(), replacing the square brackets with parentheses to fit SQL syntax.

// Get all of the rows from the database        
mTasksCursor = mDbHelper.fetchAllTasks();

ArrayList<String> activeTaskIDs = new ArrayList<String>();

// calculate which ones belong
// .....

if (!hasCompleted)             
                activeTaskIDs.add(mTasksCursor.getString(TaskerDBadapter.INDEX_ID));

// requery on my list of IDs
mTasksCursor = mDbHelper.fetchActiveTasks(activeTaskIDs);

public Cursor fetchActiveTasks(ArrayList<String> activeTaskIDs)
    {
        String inClause = activeTaskIDs.toString();
        inClause = inClause.replace('[', '(');
        inClause = inClause.replace(']', ')');

        Cursor mCursor = mDb.query(true, DATABASE_TABLE, columnStringArray(), 
                KEY_ROWID + " IN " + inClause, 
                null, null, null, null, null);

        if (mCursor != null) { mCursor.moveToFirst(); }

        return mCursor;
    }

ContentResolver cr = getContentResolver();
        Cursor groupCur = cr.query(
                Groups.CONTENT_URI, // what table/content
                new String [] {Groups._ID, Groups.NAME},    // what columns
                "Groups.NAME NOT LIKE + 'System Group:%'", // where clause(s)
                null, // ???
                Groups.NAME + " ASC" // sort order
        );

The "What Columns" piece above is where you can tell the cursor which rows to return. Using "null" returns them all.

I need to do some calculations that are impossible in the SQLite WHERE clause

I find this very hard to believe; my experience has been that SQL will let you query for just about anything you'd ever need (with the exception of heirarchical or recursive queries in SQLite's case). If there's some function you need that isn't supported, you can add it easily with sqlite_create_function() and use it in your app. Or perhaps a creative use of the SELECT clause can do what you are looking for.

Can you explain what these impossible calculations are?

EDIT: Nevermind, checking out this webpage reveals that the sqlite_create_function() adapter is all closed up by the Android SQLite wrapper. That's annoying.