Loading next page from json data to listview (endless scroll)

Question

Everything is working smoothly, but when I scroll to the bottom of the list view the list view refreshes with the next page, and doesn't append to the bottom of the list view. How can I have so the new data gets placed beneath the current data?

My Code

        @Override
            public void onScrollStateChanged(AbsListView listView, int scrollState) {
                if (scrollState == SCROLL_STATE_IDLE) {
                    if (listView.getLastVisiblePosition() >= listView.getCount() - 1 - 1) {
                        CURRENT_PAGE_NUMBER = CURRENT_PAGE_NUMBER + 25;

                        Toast.makeText(getActivity(), CURRENT_PAGE_NUMBER + " - " + JSON_AFTER, Toast.LENGTH_SHORT).show();

                        GetBlogPost getBlogPost = new GetBlogPost();
                        getBlogPost.execute();
                        adapter.notifyDataSetChanged();
                    }
                }
            }

private class GetBlogPost extends AsyncTask<Object, Void, JSONObject> {
    @Override
    protected JSONObject doInBackground(Object... params) {
        int responseCode;
        JSONObject jsonResponse = null;
        StringBuilder builder = new StringBuilder();
        HttpClient client = new DefaultHttpClient();
        HttpGet httpget = new HttpGet("http://www.website.com/" + SUBS[Integer.parseInt(SUB)] + "/.json?count=" + CURRENT_PAGE_NUMBER + "&after=" + JSON_AFTER );

        try {
            HttpResponse response = client.execute(httpget);
            StatusLine statusLine = response.getStatusLine();
            responseCode = statusLine.getStatusCode();

            if (responseCode == HttpURLConnection.HTTP_OK) {
                HttpEntity entity = response.getEntity();
                InputStream content = entity.getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(content));
                String line;
                while((line = reader.readLine()) != null){
                    builder.append(line);
                }

                jsonResponse = new JSONObject(builder.toString());
            }
            else {
                Log.i(TAG, String.format("Unsuccessful HTTP response code: %d", responseCode));
            }
        }
        catch (JSONException e) {
            Log.v(TAG, "Exception caught!", e);
        }
        catch (Exception e) {
            Log.v(TAG, "Exception caught!", e);
        }

        return jsonResponse;
    }

    @Override
    protected void onPostExecute(JSONObject result) {
        mBlogData = result;
        handleAsyncResponse();
    }
}

private void handleAsyncResponse() {
    if (mBlogData != null) {
        try {
            JSONObject jsonData = mBlogData.getJSONObject("data");
            JSONArray jsonChildren = jsonData.getJSONArray("children");
            mPostTitles = new String[jsonChildren.length()];

            for (int i = 0; i < jsonChildren.length(); i ++) {
                JSONObject children = jsonChildren.getJSONObject(i);
                JSONObject post = children.getJSONObject("data");

                JSON_AFTER = jsonData.getString("after");

                String title = post.getString("title");
                title = Html.fromHtml(title).toString();
                mPostTitles[i] = title;

                Target.add(title);

                ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_1, Target);
                setListAdapter(adapter);

                adapter = new ArrayAdapter<String>(
                        getActivity(),
                        android.R.layout.simple_list_item_1,
                        Target
                );

                setListAdapter(adapter);
            }

        } catch (JSONException e) {
            Log.wtf(TAG, "Exception caught!", e);
        }
    } else {
        Toast.makeText(
                getActivity(),
                "Nothing to display!",
                Toast.LENGTH_SHORT).show();
    }
}

score 1 · Accepted Answer · answered Mar 05 '14 at 04:35

1

The problem come from here

adapter = new ArrayAdapter<String>...
setListAdapter(adapter);

You should keep the adapter somewhere, after loading new json data, try to append it to the existing adapter and request invalidate the list view

answered Mar 05 '14 at 04:35

VinhNT

1,091
8
13

How would I go about keeping the adapter somewhere else? – Eric Goncalves Mar 05 '14 at 04:36
1

some thing like this ListView lstView; ArrayList Target = new ArrayList(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); lstView = getListView(); lstView.setChoiceMode(ListView.CHOICE_MODE_SINGLE); lstView.setTextFilterEnabled(true); Target.add("hi"); Target.add("hello"); ; ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_checked, Target); setListAdapter(adapter); Target.add("myname"); adapter.notifyDataSetChanged(); } } – VinhNT Mar 05 '14 at 04:44
I replaced a few lines of code in the "HandleBlogResponse" class, but now when i scroll to the bottom, i get a null pointer exception. any idea why? – Eric Goncalves Mar 05 '14 at 05:08
private adapter; loadListView() { initadapter() } dataincome() { pustdatatoadapter(adapter, data) adapter.notifyDataSetChanged(); } – VinhNT Mar 05 '14 at 06:08

score 0 · Answer 2 · edited Jan 04 '23 at 12:08

0

After getting data from JSON response update your adapter.

 adapter.notifyDataSetChanged();

edited Jan 04 '23 at 12:08

Martijn Pieters

1,048,767
296
4,058
3,343

answered Mar 05 '14 at 04:41

Arvind Kanjariya

2,089
1
18
23

Isnt that just checking if scroll to bottom too? – Eric Goncalves Mar 05 '14 at 04:43
no and also you can set number of item i means update listview when 3 item remaining or as you set – Arvind Kanjariya Mar 05 '14 at 04:47
I already try this and this is woking fine...In my case I update listview after every 30 item load and new item added when I reach at 27th item in list – Arvind Kanjariya Mar 05 '14 at 04:49

Loading next page from json data to listview (endless scroll)

2 Answers2