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);
}
Use the LIMIT statement in the SQL query in this way:
ReplyDeleteSELECT 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>*/);