auto load more items with android

Question

i have this code which bring JSON data from the website and it's working very fine

whai i want to do is, load 10 items and when the user scroll to the bottom it loads another 10 items ...etc until the items finished

public class MainActivity extends Activity  {
    private static final String TAG = MainActivity.class.getSimpleName();
    private ListView listView;
    private FeedListAdapter listAdapter;
    private List<FeedItem> feedItems;

    //Feeds URL - Your Website URL where you uploaded the admin panel
    private String URL_FEED = "http://EXAMPLE.COM";


    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);




        //Getting feeds from the website into listview 
        listView = (ListView) findViewById(R.id.list);
        feedItems = new ArrayList<FeedItem>();
        listAdapter = new FeedListAdapter(this, feedItems);
        listView.setAdapter(listAdapter);



            // making fresh volley request and getting json
            JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
                    URL_FEED, null, new Response.Listener<JSONObject>() {

                        @Override
                        public void onResponse(JSONObject response) {
                            VolleyLog.d(TAG, "Response: " + response.toString());
                            if (response != null) {
                                parseJsonFeed(response);
                            }
                        }
                    }, new Response.ErrorListener() {

                        @Override
                        public void onErrorResponse(VolleyError error) {
                            VolleyLog.d(TAG, "Error: " + error.getMessage());
                        }
                    });

            // Adding request to volley request queue
            AppController.getInstance().addToRequestQueue(jsonReq);


    }

    /**
     * Parsing json reponse and passing the data to feed view list adapter
     * */
    private void parseJsonFeed(JSONObject response) {
        try {
            JSONArray feedArray = response.getJSONArray("feed");

            for (int i = 0; i < feedArray.length(); i++) {
                JSONObject feedObj = (JSONObject) feedArray.get(i);

                FeedItem item = new FeedItem();
                item.setId(feedObj.getInt("id"));
                item.setName(feedObj.getString("name"));

                // Image might be null sometimes
                String image = feedObj.isNull("image") ? null : feedObj
                        .getString("image");
                item.setImge(image);
                item.setStatus(feedObj.getString("status"));
                item.setProfilePic(feedObj.getString("profilePic"));
                item.setTimeStamp(feedObj.getString("timeStamp"));

                // url might be null sometimes
                String feedUrl = feedObj.isNull("url") ? null : feedObj
                        .getString("url");
                item.setUrl(feedUrl);

                feedItems.add(item);
            }

            // notify data changes to list adapater
            listAdapter.notifyDataSetChanged();
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }


    ///Menus functions
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int itemId = item.getItemId();

        switch (itemId) {
        case R.id.action_logout:
            session.logoutUser();
            break;
        case R.id.myProfile:
            Intent intent2 = new Intent(this, ProfileActivity.class);
            startActivity(intent2);
            break;
        case R.id.addPhoto:
            Intent intent1 = new Intent(this, UploadPhoto.class);
            startActivity(intent1);
            break;
        }

        // TODO Auto-generated method stub
        return super.onOptionsItemSelected(item);
    }



}

Answer 1

implement the onscrolllistener()

public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    this.currentFirstVisibleItem = firstVisibleItem;
    this.currentVisibleItemCount = visibleItemCount;
}

public void onScrollStateChanged(AbsListView view, int scrollState) {
    this.currentScrollState = scrollState;
    this.isScrollCompleted();
 }

private void isScrollCompleted() {
    if (this.currentVisibleItemCount > 0 && this.currentScrollState == SCROLL_STATE_IDLE) {
        /*** In this way I detect if there's been a scroll which has completed ***/
        /*** do the work for load more date! ***/
        if(!isLoading){
             isLoading = true;
             GetMoreJsonData();
        }
    }
}

as you implement and add this listener to your listview this will detect for the end of listview as scroll position was at end of list just get more data. And during the loading data you need one flag to load data at once when the scroll position goes to end. So if data is loading and during that time you scroll up then scroll down then it will not get more data for duplication.

You can create a new method and move you code of making fresh volley request and getting json in it:

private void GetMoreJsonData()
{
    // making fresh volley request and getting json
    JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
            URL_FEED, null, new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    VolleyLog.d(TAG, "Response: " + response.toString());
                    if (response != null) {
                        parseJsonFeed(response);
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    VolleyLog.d(TAG, "Error: " + error.getMessage());
                }
            });

    // Adding request to volley request queue
    AppController.getInstance().addToRequestQueue(jsonReq);     
}

Dont forget to get 10-10 items when you send json request