ListFragments infinite scroll don't work after switching tabs to and fro

Question

I have a application which has a main activity hosting 2 list fragments controlled by tabs (courtesy of actionbarsherlock).

Both fragments are more less same in code and load data from server dynamically. One shows latest content second shows all the content in database with endless scrolling implemented.

All works well if if use only in the following order: latestFragment -> allFragment

But when i comeback from latestFragment to allFragment allFragment -> latestFragment

Endless scroll stops working!!

I am new to android development, having studied some bits and pieces did manage to put it all together but its stuck here. I simply cant get around. then no matter what i do scroll wont work until i close app and start again.

MainActivity.java

public class MainActivity extends SlidingFragmentActivity implements OnQueryTextListener
{ protected static DisplayImageOptions options; protected static ImageLoader imageLoader; ArrayList latest; ArrayList generes;

            ActionBar.Tab latestTab;
            ActionBar.Tab AllTab;

            LatestNewsFragment latestNews;
            AllNewsFragment allNews;


            MenuItem search;
            SearchView searchView;
            ProgressBar pBar;
            SharedPreferences settings;

            protected CategoryListFragment mFrag;


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

            pBar = (ProgressBar) this.findViewById(R.id.pBar);
            pBar.setVisibility(View.GONE);

            ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(this.getApplicationContext())
            .build();

            imageLoader = ImageLoader.getInstance();
            imageLoader.init(config);

            options = new DisplayImageOptions.Builder()
            .showStubImage(R.drawable.poster)
            .delayBeforeLoading(2000)
            .showImageForEmptyUri(R.drawable.poster)
            .showImageOnFail(R.drawable.poster)
            .bitmapConfig(Bitmap.Config.RGB_565)
            .imageScaleType(ImageScaleType.NONE)
            .cacheOnDisc()
            .cacheInMemory()
            .build();

            Bundle extras = getIntent().getExtras();
            latest = extras.getParcelableArrayList("latest");
            generes = extras.getParcelableArrayList("generes");
            disclaimer = extras.getString("disclaimer");

            /* Tabs */
            getSupportActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

            /* Latest list fragment */
            latestNews = new LatestNewsFragment();
            latestNews.setImagLoader(imageLoader);
            latestNews.setImageDisplayOptions(options);
            latestNews.setData(latest);
            latestTab = getSupportActionBar().newTab().setText("Latest");
            latestTab.setTabListener(new TabListener(latestNews));
            getSupportActionBar().addTab(latestTab);

            /* All news list fragment */
            allNews = new AllNewsFragment();
            allNews.setImagLoader(imageLoader);
            allNews.setImageDisplayOptions(options);
            AllTab = getSupportActionBar().newTab().setText("Browse All");
            AllTab.setTabListener(new TabListener(allNews));
            getSupportActionBar().addTab(AllTab);

            /* Sliding menu */

            // set the Behind View
            setBehindContentView(R.layout.menu_frame);
            if (savedInstanceState == null) {
            FragmentTransaction t = this.getSupportFragmentManager().beginTransaction();
            mFrag = new CategoryListFragment();
            mFrag.setData(generes);
            t.replace(R.id.menu_frame, mFrag);
            t.commit();
            } else {
            mFrag = (CategoryListFragment)this.getSupportFragmentManager().findFragmentById(R.id.menu_frame);
            }

            // customize the SlidingMenu
            SlidingMenu sm = getSlidingMenu();
            sm.setShadowWidthRes(R.dimen.shadow_width);
            sm.setShadowDrawable(R.drawable.shadow);
            sm.setBehindOffsetRes(R.dimen.slidingmenu_offset);
            sm.setFadeDegree(0.35f);
            sm.setTouchModeAbove(SlidingMenu.TOUCHMODE_MARGIN);

            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            getSupportActionBar().setDisplayShowTitleEnabled(false);

            settings = getSharedPreferences("com.newsspace.mobile.android", Context.MODE_PRIVATE);
            boolean hasAcceptedPolicy = settings.getBoolean("disclaimeraccept", false);

            if(!hasAcceptedPolicy)
            showDisclaimer(this, disclaimer);
            }

            void showDisclaimer(final Activity context, String message)
            {
            AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);

            // Setting Dialog Title
            alertDialog.setTitle(getText(R.string.disclaimer));

            // Setting Dialog Message
            alertDialog.setMessage(message);

            // Setting Icon to Dialog
            //alertDialog.setIcon(R.drawable.delete);

            // Setting Positive "Yes" Button
            alertDialog.setPositiveButton(getText(R.string.disclaimer_agree), new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
            Editor editor = settings.edit();
            editor.putBoolean("disclaimeraccept", true);
            editor.commit();
            }
            });

            // Setting Negative "NO" Button
            alertDialog.setNegativeButton(getText(R.string.disclaimer_disagree), new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            Editor editor = settings.edit();
            editor.putBoolean("disclaimeraccept", false);
            editor.commit();
            context.finish();
            }
            });

            // Showing Alert Message
            alertDialog.show();
            }

            @Override
            public boolean onCreateOptionsMenu(Menu menu) {
            getSupportMenuInflater().inflate(R.menu.action_menu, menu);
            search = menu.findItem(R.id.search);
            SearchView searchView = (SearchView) search.getActionView();
            searchView.setOnQueryTextListener(this);
            SearchManager searchManager = (SearchManager)getSystemService(Context.SEARCH_SERVICE);
            SearchableInfo info = searchManager.getSearchableInfo(getComponentName());
            searchView.setSearchableInfo(info);

            return true;
            }





            @Override
            public boolean onOptionsItemSelected(MenuItem item) {
            switch (item.getItemId()) {
            case android.R.id.home:
            toggle();
            return true;

            case R.id.refresh:
            refreshCurrentFragment();
            return true;
            }

            return super.onOptionsItemSelected(item);
            }

            @Override
            public void onItemClick(AdapterView<?> parent, final View view, int position, long id) 
            {
            // NO OP
            }



            void refreshCurrentFragment()
            {

            }




            @Override
            public void hideProgressbar() {
            // TODO Auto-generated method stub
            pBar.setVisibility(View.GONE);
            }


            @Override
            public void showProgressbar() {
            // TODO Auto-generated method stub
            pBar.setVisibility(View.VISIBLE);
            }



            @Override
            public boolean onQueryTextSubmit(String query) {
            // TODO Auto-generated method stub 
            search.collapseActionView();
            return false;
            }



            @Override
            public boolean onQueryTextChange(String newText) {
            // TODO Auto-generated method stub
            return false;
            }


            @Override
            protected void onNewIntent(Intent intent) {
            super.onNewIntent(intent);
            handleIntent(intent);
            }

            private void handleIntent(Intent intent){
            if(Intent.ACTION_SEARCH.equals(intent.getAction())){
            String searchQuery = intent.getStringExtra(SearchManager.QUERY);
            }
            }

            }

TabListener.java

public class TabListener implements ActionBar.TabListener {

Fragment fragment;

public TabListener(Fragment fragment) {
  this.fragment = fragment;
}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub
    ft.replace(R.id.fragment_container, fragment);
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub
    ft.remove(fragment);
}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub  
}

}

AllNewsFragment.java

public class AllNewsFragment extends ListFragment implements OnRefreshListener, OnConnectivityHandler, OnScrollListener {

ArrayList<News> news;
OnNewsSelectedListener listener;
DisplayImageOptions options;
ImageLoader imageLoader;
LazyAdapter adapter;

NewsListQueryData data;
boolean canLoadNewss = true;

int page = 1;
int total = 0;
int category = 0;
String searchterm = "";
View rootview;

int mVisibleThreshold = 5;
int mPreviousTotal = 0;
boolean mLoading = true;
boolean mLastPage = false;

ConnectionManager connectionManager;
boolean isConnected;
boolean failedCall = false;
boolean activityReady = false;



public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    rootview = inflater.inflate(R.layout.list, null);
    Log.d("APP", "createView");
    return rootview;
}




@Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    Log.d("APP", "onCreate");
}




@Override
public void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
}




public void setImageDisplayOptions(DisplayImageOptions options){
    this.options = options;
}

public void setImagLoader(ImageLoader imageLoader){
    this.imageLoader = imageLoader;
}

public void setData(ArrayList<News> news){
    this.news = news;
}

public ArrayList<News> getData(){
    return this.news;
}

void init()
{
    if(news == null)
    this.news = new ArrayList<News>();

    adapter = new LazyAdapter(news, getActivity(), options, imageLoader);
    setListAdapter(adapter);

    ListView list = (ListView) this.rootview;
    list.setOnScrollListener(this);


    this.category = 0;
    this.page = 1;
    this.searchterm = "";

    this.total = 0;
    this.mPreviousTotal = 0;
    this.mLoading = true;
    this.mLastPage = false;

    connectionManager = new ConnectionManager(this.getActivity(), this);
    isConnected = connectionManager.isConnectedToInternet();
    connectionManager.regsiterForNetworkChanges();

    loadMoreNewss(category, page, searchterm);
}

public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    if(!activityReady) init();
    activityReady = true;
}

@Override
public void onListItemClick(ListView lv, View v, int position, long id) {
    News selectedNews =  (News) getListAdapter().getItem(position);
    if (selectedNews != null)
    showNewsDetails(selectedNews);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);

    try {
    listener = (OnNewsSelectedListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnHeadlineSelectedListener");
    }


}

void showNewsDetails(News news)
{
    listener.newsSelected(news);
}

@Override
public void result(Object args) {
    listener.hideProgressbar();

    // TODO Auto-generated method stub
    if(args instanceof NewsListQueryData){
    data = (NewsListQueryData) args;
    page = data.page;
    category = data.category;
    searchterm = data.searchterm;
    total = data.total;
    appendData(data.news);
    canLoadNewss = true;
    }
}

@Override
public void fault(Object args) {
    // TODO Auto-generated method stub
    listener.hideProgressbar();
    canLoadNewss = true;
    Toast.makeText(this.getActivity(), R.string.loading_reported_failed, Toast.LENGTH_LONG).show();
}

@Override
public void started(Object args) {
    // TODO Auto-generated method stub
    listener.showProgressbar();
}

@SuppressWarnings("unchecked")
void loadMoreNewss(int category, int page, String searchterm)
{
    if(canLoadNewss){
        if(isConnected){
        new LoadNewsTask(this).execute(Constants.SEARCH_SCRIPT, category, searchterm, page);
        canLoadNewss = false;
        failedCall = false;
        }
        else{
        failedCall = true;
        connectionManager.showProgressDialog();
        }       
    }
}

void appendData(ArrayList<News> news)
{
    for(int i=0;i<news.size();i++)
    adapter.add(news.get(i));
    adapter.notifyDataSetChanged();
}

@Override
public void onScroll(AbsListView view, int firstVisible, int visibleCount, int totalCount) {
    if (mLoading) {
        if (totalCount > mPreviousTotal) {
            mLoading = false;
            mPreviousTotal = totalCount;
            page++;

            // Find your own condition in order to know when you have finished displaying all items
            if (page + 1 > total) {
            mLastPage = true;
            }
        }
    }
    if (!mLastPage && !mLoading && (totalCount - visibleCount) <= (firstVisible + mVisibleThreshold)) {
        loadMoreNewss(category, page, searchterm);
        mLoading = true;
    }
}

@Override
public void onScrollStateChanged(AbsListView arg0, int arg1) {
    // TODO Auto-generated method stub

}

@Override
public void connectToInternet() {
    // TODO Auto-generated method stub

}

@Override
public void doNotConnectToInternet() {
    // TODO Auto-generated method stub

}

@Override
public void connectionStatusChanged() {
    /*
    // TODO Auto-generated method stub
    isConnected = connectionManager.isConnectedToInternet();
    if(isConnected){
    connectionManager.hideProgressDialog();
    if(failedCall) loadMoreNewss(category, page, searchterm);
    }else{
    connectionManager.showProgressDialog();
    }
    */
}

void emptyAdapter()
{
    adapter.clear();
    adapter.notifyDataSetChanged();
}

@Override
public void refresh() 
{
    this.page = 1;
    this.total = 0;
    this.mPreviousTotal = 0;
    this.mLoading = true;
    this.mLastPage = false;

    if(adapter != null) 
    emptyAdapter();

    loadMoreNewss(category, page, searchterm);      
}

}

Furthermore latestNews Fragment is exactly the same as AllNewsFragment except for the endless scroll. I can post here is needed. but i thing this much is good. Please help me find a answer to this problem.

Answer 1

Hopefully you got your solution by now. But anyway, I got it working by moving following lines from init to outside if(!activityReady) block in onActivityCreated

ListView list = (ListView) this.rootview;
list.setOnScrollListener(this);