How to update listview whose data was queried from database through SimpleCursorAdapter?

Question

I want to show the items queried from database in the listview with SimpleCursorAdapter. For example, there may be 20,000 items in the database. I want to just load 100 items(_id : 1-100) queried instead of load all items, when scrolling in the end of listview, load another 100 items(_id : 101-200) queried, how to achieve it? Any suggestion is welcome, thanks.

Relative codes are as follows:

protected void onCreate(Bundle savedInstanceState) {
    mCursor = managedQuery(CONTENT_URI, PROJECTION, null, null, "_id DESC");
    mAdapter = new SimpleCursorAdapter(this,R.layout.list_content,  mCursor, keys,  values);
    setListAdapter(mAdapter);
}

In my defined listview, i want to load more items by query database.

public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) 
{
    int lastItem = firstVisibleItem + visibleItemCount - 1;

    if (mListAdapter != null) {
        if ((lastItem == mListAdapter.getCount()-1) && (mRefreshState != REFRESHING)) {
            mFooterView.setVisibility(View.VISIBLE);
            mRefreshState = REFRESHING;
            new Handler().postDelayed(new Runnable() {  
                public void run() {  
                    //execute the task ,  i want to load more items by query database
                    RefreshListView(LOADING_STORED_INFO);                                           
                }  
             }, DEFAULT_DELAY_TIMER);           
        }
    }
}

In the AsyncTask loading data, i do the query operation.

    protected Integer doInBackground(Integer... params)
    { 
        Uri uri = ContentUris.withAppendedId(CONTENT_URI, mCursor.getInt(0)-1);
        cursor = managedQuery(uri, PROJECTION, null, null, "_id DESC");
        return (0 == params[0]) ? 1 : 0;
    }

    @Override
    protected void onPostExecute(Integer result)
    {
        mAdapter.changeCursor(cursor);//is this OK?
        mAdapter.notifyDataSetChanged();
        /*
        if (1 == result)
        {
            mListView.setSelection(1);
        }
        else
        {
            mListView.setSelection(mCount-1);               
        }*/
        // Call onRefreshComplete when the list has been refreshed.
        mListView.onRefreshComplete(result); 
        super.onPostExecute(result);
    }

Relative codes are as follows: – breeze Jan 15 '12 at 13:00 — breeze, Jan 15 '12 at 13:00

Francesco Vadicamo · Accepted Answer · 2012-01-15T18:02:41.513

2

Use the LIMIT statement in the SQL query in this way:

SELECT your_column FROM your_table ORDER BY your_order LIMIT limit_skip, limit_count

Then you can use a OnScrollListener to retrieve the index of the first visible cell and the number of visible cells so you can increment limit_skip and limit_count coherently.

Instead of the generic AsyncTask use a CursorLoader and implement LoaderManager.LoaderCallbacks<Cursor> as follow:

public Loader<Cursor> onCreateLoader(int id, Bundle args){
    String orderBy = "_id DESC"
    if(args != null){
        orderBy += " LIMIT " + args.getInt("LIMIT_SKIP") + "," + args.getInt("LIMIT_COUNT");
    }

    return new CursorLoader(this /*context*/, CONTENT_URI, PROJECTION, null, null, orderBy);
}

public void onLoadFinished(Loader<Cursor> loader, Cursor data){
    listAdapter.swapCursor(data);
}

public void onLoaderReset(Loader<Cursor> loader){
    listAdapter.swapCursor(null);
}

Then, in onCreate(), pass null as cursor to new SimpleCursorAdapter() and create the CursorLoader in this way:

getLoaderManager().initLoader(0, null, this /*LoaderCallbacks<Cursor>*/);

Then, in onScroll(), reset everytime the loader in this way:

Bundle args = new Bundle();
args.putInt("LIMIT_SKIP", limit_skip_value);
args.putInt("LIMIT_COUNT", limit_count_value);
getLoaderManager().restartLoader(0, args, this /*LoaderCallbacks<Cursor>*/);

edited Jan 15 '12 at 18:02

answered Jan 15 '12 at 09:55

Francesco Vadicamo

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I used ContentProvider's query function instead of ues sql query. my problem is that how to change cursor to ensure the count of listview items is increased when queried more items.I used changeCursor and notifyDataSetChanged function but there is no use. – breeze Jan 15 '12 at 10:18
Please, edit your question and add your code so we can help you better. – Francesco Vadicamo Jan 15 '12 at 10:33
@breeze try it and let me know! – Francesco Vadicamo Jan 15 '12 at 18:04
I got an error information when compile onCreateLoader. "Type mismatch: cannot convert from CursorLoader to Loader".But no error was found while compile the sample code LoaderThrottle.java – breeze Jan 16 '12 at 02:12
I find a class MergeCursors which can support help for my current problem.Thanks for your participation. – breeze Jan 16 '12 at 06:30
Hi Francesco Vadicamo, I tried your above solution for a list which has orderBy = "date ASC"; and limit of 15. Limit is stack from bottom. When I scroll the cursor is updated but Focus is transfered to bottom record. I tried using ListView.setselection(); and other methods but same thing happens. can you please tell me any work around?? – om252345 Oct 03 '12 at 12:04

How to update listview whose data was queried from database through SimpleCursorAdapter?

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