call public class and refresh list view in the activity

Question

i have a MainActivity with a list view. in this activity is a private void showList() which query all of my database and show it in the list view.

i have another public class "Sync" which send an http post to my MYSQL Database, get the result and write this into the android database.

i would like to realize, that on each resume of the main activity, the public class Sync will call and on finish the list view in the main activity should be refresh.

in the MainActivity, i call it like this:

@Override
public void onResume() {
   super.onResume();
   new Sync.SyncMYSQL(context).execute();
}

this is the Sync Class:

public class Sync {


        // MYSQL => Database
        static class SyncMYSQL extends AsyncTask<String, String, String> {

            Context context;

            public SyncMYSQL(Context c) {
                this.context = c;
            }


            @Override
            protected String doInBackground(String... params) {
                try {

                       // DO SOMETHING


                } catch (MalformedURLException e) {
                    Log.e("-->", Log.getStackTraceString(e));
                } catch (IOException e) {
                    Log.e("-->", Log.getStackTraceString(e));
                }
                return null;
            }


            protected void onPostExecute(String result) {

                // DO SOMETHING

            }
        }

MainActivity

public class OverviewData extends Fragment {

    private View FragementView;
    DatabaseHandler dbHandler;
    ListView ListView;
    DatabaseListAdapter databaseListAdapter;
    Context context;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        context = getContext();

        FragementView = inflater.inflate(R.layout.overview, container, false);
        ListView = (ListView) FragementView.findViewById(R.id.listView);

        dbHandler = new DatabaseHandler(getActivity());

        showList();

        return FragementView;
    }


    @Override
    public void onResume() {
        super.onResume();
        new Sync.SyncMYSQL(context, 0).execute();
    }




    private void showList() {

        ArrayList<DatabaseListItems> databaseList = new ArrayList<>();
        databaseList.clear();

        String query = "SELECT * FROM " + DatabaseHelper.DATABASE_TABLE;

        Cursor c1 = dbHandler.selectQuery(query);
        if (c1 != null && c1.getCount() != 0) {
            if (c1.moveToFirst()) {
                do {
                    DatabaseListItems databaseListItems = new DatabaseListItems();

                    databaseListItems.setIdentifier(c1.getString(c1.getColumnIndex(DatabaseHelper.COLUMN_ID)));

                    databaseList.add(databaseListItems);

                } while (c1.moveToNext()) ;
            }
            c1.close();

        }


        databaseListAdapter = new DatabaseListAdapter(getActivity(), databaseList);
        ListView.setAdapter(databaseListAdapter);
    }
}

the problem is, that i dont know, how i can refresh the list view of the main activity AFTER the Sync process ist executed — Stack108, May 27 '16 at 08:33
there is nothing in `doInBackground()` how are you taking the data from server? — Devendra Singh, May 27 '16 at 08:36
this part i comment out, because that is not important, fact is: i get data of my MYSQL Database and this data will write in the android database. but now i have to find a way to refresh the list view, to show the new data — Stack108, May 27 '16 at 08:37
ok, when you saved the data in the `SQLite` pass the data to adapter too and call `notifiyDataSetChanged()` — Devendra Singh, May 27 '16 at 08:39
Before just use dataList notifyDataSetChanged in the last line — Meghal Agrawal, May 27 '16 at 08:47

score 0 · Answer 1 · answered May 27 '16 at 08:39

0

For the listView adapter -

firstly set the data like

adapter=new Adapter(context,newDataList);

adapter.notifyDatasetChanged();

answered May 27 '16 at 08:39

Meghal Agrawal

177
10

mmmh, maybe i have to say that i use a custom list view adapter. i will post the showList Function in my first post now – Stack108 May 27 '16 at 08:42
I am talking about custom list view adapter only! make a constructor in adapter class to receive dataList. – Meghal Agrawal May 27 '16 at 08:45
sry, but i dont know what i have to do, where should i put your code? int the post onPostExecute of the Sync class? – Stack108 May 27 '16 at 08:51

Dhaval Parmar · Answer 2 · 2016-05-27T10:18:59.127

0

its bad idea to refresh list data every time in onResume(because, its load data whenever you open and close activity, or come back from last activity) instead of that call sync method in onStart/onCreate(at end of onCreate).

To refresh listview use interface. implement interface in activity and add below code in interface method after that call interface method from onPostExecute

if(databaseListAdapter != null)
databaseListAdapter.notifyDataSetChanged();

edited May 27 '16 at 10:18

answered May 27 '16 at 10:04

Dhaval Parmar

18,812
8
82
177

if i only put this code to my `onPostExecute`, i get the error: `cannot find symbol variable databaseListAdapter` – Stack108 May 27 '16 at 10:10
check edited answer and here is answer how to use interface http://stackoverflow.com/a/12142530/1168654 – Dhaval Parmar May 27 '16 at 10:19
what do you mean with implement interface? – Stack108 May 27 '16 at 10:21
sry sry sry, but can you tell me where i have to put the code into my code parts? i try to implement the interface - but i think that this is not correctly – Stack108 May 27 '16 at 11:14

score 0 · Answer 3 · answered May 27 '16 at 10:15

Use a cursor loader. As soon as you database changes the cursor loader will call onLoadFinished() in which you can update your list view.

Initialize a loader:

getLoaderManager().initLoader(1, null, this);

In your onResume() restart it:

getLoaderManager().restartLoader(1, null, this);

In onDetach()/onDestroy() destroy it:

getLoaderManager().destroyLoader(1);

Make your class implement: LoaderManager.LoaderCallbacks And you will have to override its three main methods. onLoadFinished() will help you yo update the UI/list view.

call public class and refresh list view in the activity

3 Answers3