CODEWITHSUNDEEP
androiddatabaselistviewandroid-asynctask
Sviatoslav
Sviatoslav

Reputation: 1312

How to update ListView from AsyncTask?

I am loading images by using AsyncTask and for updating ListView I am using notifyDataSetChanged() method.

But notifyDataSetChanged() doesn't change anything in the ListView onProgressUpdate(). I don't want to use cursor.requery because it is deprecated method.

Why notifyDataSetChanged() is not working for me?

public class News extends BasicActivity implements OnItemClickListener{
private SQLiteDatabase db = null;
private ListView lvNews;
private TaskImgSm taskImgSm = null;
private NewsListAdapter adapter;
private Cursor cur;
boolean pause = false;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.news);

    db = SQLiteDatabase.openDatabase(((MyApp) getApplication()).getDbPath(), null, SQLiteDatabase.OPEN_READWRITE);
    lvNews = (ListView) findViewById(R.id.list_news);
    lvNews.setOnItemClickListener(this);
    listFilling();

    if (taskImgSm != null && taskImgSm.getStatus() != AsyncTask.Status.FINISHED) taskImgSm.cancel(true);
    taskImgSm = new TaskImgSm();
    taskImgSm.execute();        
}

private void listFilling() {
    cur = db.query("news", new String[] { "_id", "id_news", "title", "date", "img_url", "img_sm" }, null, null, null, null, null);
    startManagingCursor(cur);
    adapter = new NewsListAdapter(this, cur, db);
    lvNews.setAdapter(adapter);
    adapter.notifyDataSetChanged();
}

class TaskImgSm extends AsyncTask<Void, String, Void> {
    Cursor curs;
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        curs = db.query("news", new String[] { "_id", "id_news", "img_url", "img_sm" }, null, null, null, null, null);
        startManagingCursor(curs);
    }

    @Override
    protected Void doInBackground(Void... unused) {
        curs.moveToFirst();
        while (curs.isAfterLast() == false) {
            if (curs.getBlob(curs.getColumnIndex("img_sm")) == null) {
                String imgUrl = curs.getString(curs.getColumnIndex("img_url"));
                String idNews = curs.getString(curs.getColumnIndex("id_news"));
                updateImg(imgUrl, idNews, "img_sm");
                publishProgress();
            }
            curs.moveToNext();
        }           
        return (null);
    }

    private void updateImg(String img_URL, String whereId, String imgColumn) {
        try {
            DefaultHttpClient mHttpClient = new DefaultHttpClient();
            HttpGet mHttpGet = new HttpGet();
            mHttpGet.setURI(new URI(img_URL));
            HttpResponse mHttpResponse = mHttpClient.execute(mHttpGet);
            if (mHttpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
                HttpEntity entity = mHttpResponse.getEntity();
                if (entity != null) {
                    // insert to database
                    ContentValues values = new ContentValues();
                    values.put(imgColumn, EntityUtils.toByteArray(entity));
                    db.update("news", values, "id_news=" + whereId, null);
                }
            }
        } catch (URISyntaxException e) {e.printStackTrace();
        } catch (ClientProtocolException e) {e.printStackTrace();
        } catch (IOException e) {e.printStackTrace();}
    }

    @Override
    protected void onProgressUpdate(String... item) {
        if (pause == false) {
            adapter.notifyDataSetChanged();
        }
    }

    @Override
    protected void onPostExecute(Void unused) {}
}

@Override
protected void onPause() {
    pause = true;
    super.onPause();
}

@Override
protected void onResume() {
    pause = false;
    adapter.notifyDataSetChanged();
    super.onResume();
}

@Override
protected void onDestroy() {
    if (taskImgSm != null && taskImgSm.getStatus() != AsyncTask.Status.FINISHED) taskImgSm.cancel(true);
    super.onDestroy();
}
}

Upvotes: 1

Views: 4659

Answers (3)

Etienne Lawlor
Etienne Lawlor

Reputation: 6687

I think you may want to update the ImageView in a ListView in the onPostExecute() method. This is how I accomplished something similar to what you are doing : Multithreading For Performance

Upvotes: 0

dmon
dmon

Reputation: 30168

The reason it's not working is because notifyDataSetChanged() only tells the ListView that the data in the adapter has changed. Since that data hasn't changed (because you haven't queried the database again), then the ListView won't show any updates. You need to execute the query again and update the data in the adapter, then call notifyDatasetChanged().

Upvotes: 2

Mathieu Hausherr
Mathieu Hausherr

Reputation: 3485

Why don't use a ContentProvider.

With a ContentProvider you can update your table with the notifyChange(uri) method

Tutorial for that here http://thinkandroid.wordpress.com/2010/01/13/writing-your-own-contentprovider/

Upvotes: 1

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