I'm new to Android and got stuck on one moment. I have working practice in a company, but I have no people to give an advice. My application is something like RSS feed. I have to load data from API which returns me JSON object. The address of API is http://itvdn-api.azurewebsites.net/api/news/1. There are only 4 pages for now. I'm loading info from the first page instantly, then when there are 2 items left I'm trying to load the next one. It loads 2nd page but then it stops loading. I tried to debug and after it parses 3rd page I'm throwed to AbsListView.java. The applications works fine, without any crashes.
This is Fragment class where I'm representing parsed data.
public class NewsFragment extends android.support.v4.app.Fragment implements AbsListView.OnItemClickListener {
private static final String ARG_SECTION_NUMBER = "section_number";
private ArrayList<NewsBlogData> newsData;
private OnFragmentInteractionListener mListener;
/**
* The fragment's ListView/GridView.
*/
private AbsListView mListView;
/**
* The Adapter which will be used to populate the ListView/GridView with
* Views.
*/
private NewsBlogItemAdapter mAdapter;
// TODO: Rename and change types of parameters
public static NewsFragment newInstance(int sectionNumber) {
NewsFragment fragment = new NewsFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public NewsFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// TODO: Change Adapter to display your content
/*mAdapter = new ArrayAdapter<DummyContent.DummyItem>(getActivity(),
android.R.layout.simple_list_item_1, android.R.id.text1, DummyContent.News);*/
newsData = new ParserJson().getNewsBlogData(1);
mAdapter = new NewsBlogItemAdapter(getActivity(),
R.layout.news_blog_list_item,
newsData);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_news, container, false);
// Set the adapter
mListView = (AbsListView) view.findViewById(android.R.id.list);
mListView.setAdapter(mAdapter);
// Set OnItemClickListener so we can be notified on item clicks
mListView.setOnItemClickListener(this);
//mListView.setOnScrollListener(new EndlessScrollListener());
mListView.setOnScrollListener(new EndlessScrollListener() {
@Override
public void onLoadMore(int page, int totalItemsCount) {
// TODO Auto-generated method stub
newsData.addAll(new ParserJson().getNewsBlogData(page));
}
});
return view;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (OnFragmentInteractionListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnFragmentInteractionListener");
}
((NavigationActivity) activity).onSectionAttached(
getArguments().getInt(ARG_SECTION_NUMBER));
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//FragmentManager fragmentManager = NavigationActivity.getSupportFragmentManager();
}
/**
* The default content for this Fragment has a TextView that is shown when
* the list is empty. If you would like to change the text, call this method
* to supply the text it should use.
*/
public void setEmptyText(CharSequence emptyText) {
View emptyView = mListView.getEmptyView();
if (emptyView instanceof TextView) {
((TextView) emptyView).setText(emptyText);
}
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onNewsFragmentInteraction(String id);
}
}
This is EndlessScrollListener that I found on endless scroll list view
public abstract class EndlessScrollListener implements AbsListView.OnScrollListener {
// The minimum amount of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 2;
// The current offset index of data you have loaded
private int currentPage = 0;
// The total number of items in the dataset after the last load
private int previousTotalItemCount = 0;
// True if we are still waiting for the last set of data to load.
private boolean loading = true;
// Sets the starting page index
private int startingPageIndex = 1;
public EndlessScrollListener() {
}
public EndlessScrollListener(int visibleThreshold) {
this.visibleThreshold = visibleThreshold;
}
public EndlessScrollListener(int visibleThreshold, int startPage) {
this.visibleThreshold = visibleThreshold;
this.startingPageIndex = startPage;
this.currentPage = startPage;
}
// This happens many times a second during a scroll, so be wary of the code
// you place here.
// We are given a few useful parameters to help us work out if we need to
// load some more data,
// but first we check if we are waiting for the previous load to finish.
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// If the total item count is zero and the previous isn't, assume the
// list is invalidated and should be reset back to initial state
// If there are no items in the list, assume that initial items are
// loading
if (!loading && (totalItemCount < previousTotalItemCount)) {
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = totalItemCount;
if (totalItemCount == 0) {
this.loading = true;
}
}
// If it’s still loading, we check to see if the dataset count has
// changed, if so we conclude it has finished loading and update the
// current page
// number and total item count.
if (loading) {
if (totalItemCount > previousTotalItemCount) {
loading = false;
previousTotalItemCount = totalItemCount;
currentPage++;
}
}
// If it isn’t currently loading, we check to see if we have breached
// the visibleThreshold and need to reload more data.
// If we do need to reload some more data, we execute onLoadMore to
// fetch the data.
if (!loading
&& (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
onLoadMore(currentPage + 1, totalItemCount);
loading = true;
}
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page, int totalItemsCount);
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// Don't take any action on changed
}
}
Please tell me if I can do the whole thing in other way, or may be I should attach another code or log data.
I found the answer on stackoverflow. Now my fragment implements OnScrollListener instead of making separate class.
My code looks like this
public class NewsFragment extends android.support.v4.app.Fragment implements
AbsListView.OnItemClickListener, AbsListView.OnScrollListener {
private static final String ARG_SECTION_NUMBER = "section_number";
// Amount of items in the end of the list that should trigger the loading
private int threshold = 2;
// The index of the page from where I'm loading data
private int currentPage = 1;
// The list that is represented in the ListView
private ArrayList<NewsBlogData> newsData;
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
//leave this empty
}
@Override
public void onScrollStateChanged(AbsListView listView, int scrollState) {
if (scrollState == SCROLL_STATE_IDLE) {
if (listView.getLastVisiblePosition() >= listView.getCount() - 1 - threshold) {
currentPage++;
//load more list items:
newsData.addAll(new ParserJson().getNewsBlogData(currentPage));
mAdapter.notifyDataSetChanged();
}
}
}
Found this answer over here Android Endless List
Added only
mAdapter.notifyDataSetChanged();
Because data was loading not from the main thread.
Probably it should work with EndlessScrollListener as a separate class, but i didn't test it out.