android- Replacing fragment in ViewPager from NavigationBar

Question

I'm developing an Android application that allow to view the results of hockey matches. I'm using a ViewPager with a custom FragmentPagerAdapter to display three fragments,and a NavigationDrawer with an ExpandableListView,used to display the championships. When I click on the ExpandableListView childrens,I want to update the three fragments with the data of the selected championship.

I set an OnchildClickListener in the NavigationDrawer,where I istantiated a FragmentManager and called replace() method. But it just returns a blank screen.

I searched in every forum and tried different solutions,but no one was effective When I use ft.add() instead of ft.replace() and I refresh the page with the SwipeRefreshLayout,I get the correct result,but I want to get it without manually refreshing the page. I also tried to replace FragmentPagerAdapter with FragmentStatePagerAdapter,but nothing changed.

NavigationDrawerFragment

 package com.dcdeveloper.fihresults;

    public class NavigationDrawerFragment extends Fragment {

    /**
     * Immagazzina lo stato della posizione dell'elemento selezionato.
     */
    private static final String STATE_SELECTED_POSITION = "selected_navigation_drawer_position";

    /**
     * Per the design guidelines, you should show the drawer on launch until the user manually
     * expands it. This shared preference tracks this.
     */
    private static final String PREF_USER_LEARNED_DRAWER = "navigation_drawer_learned";

    /**
     * A pointer to the current callbacks instance (the Activity).
     */
    private NavigationDrawerCallbacks mCallbacks;

    /**
     * Helper component that ties the action bar to the navigation drawer.
     */
    private ActionBarDrawerToggle mDrawerToggle;
    /**
     * Memorizza l'istanza del DrawerLayout
     */
    private DrawerLayout mDrawerLayout;
    /**View di questa barra di navigazione*/
    private View mFragmentContainerView;
    /**Posizione dell'elemento selezionato all'interno della lista*/
    private int mCurrentSelectedPosition = 0;
    private boolean mFromSavedInstanceState;
    /**Boolean che indica se l'utente è venuto a conoscenza dell'utilizzo della barra laterale.Utilizzato per accessibilità.*/
    private boolean mUserLearnedDrawer;
    private ActionBarDrawerToggle actionBarDrawerToggle;
    /**Lista con elementi espandibili,contiene i dati relativi ai campionati*/
    ExpandableListView expListView;
    /**adapter per inserire i dati nella ExpandableListView*/
    MyExpandableListAdapter expandableListAdapter;
    /*ArrayList dei titoli dei campionati*/
    List<String> listDataHeader;
    /**Hashmap contenente i dati relativi ai campionati,collegati ai relativi titoli*/
    HashMap<String, List<String>> listDataChild;
    HashMap<Campionato,Integer>listaCampionati;
    /**Stringa contenente l'url del WS a cui si effettueranno le richieste HTTP per ricevere i dati dei campionati*/
    String wsURL;
    /**ID del campionato,utilizzato per aggiornare le pagine una volta premuto l'elemento di un campionato nella lista*/
    protected int key;
    /**Memorizza il titolo dell'Activity,in modo da cambiare il titolo della MainActivity*/
    CharSequence mDrawerTitle;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Read in the flag indicating whether or not the user has demonstrated awareness of the
        // drawer. See PREF_USER_LEARNED_DRAWER for details.
        SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity());
        mUserLearnedDrawer = sp.getBoolean(PREF_USER_LEARNED_DRAWER, false);

        if (savedInstanceState != null) {
            mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
            mFromSavedInstanceState = true;
        }

        // Select either the default item (0) or the last selected item.
        selectItem(mCurrentSelectedPosition);
        //Stringa contenente l'url del Web Service
        wsURL = "http://fihresults.altervista.org/WebServiceFihResults/service.php";
        //Prepara le intestazioni standard dei campionati
        prepareHeaderData();

    }

    /**
     * Metodo costruttore della view.Utilizza il layout predefinito del frammento.
     * I dati inseriti all'interno del ListLayout vengono ricevuti dal server ed organizzati
     * all' interno della lista.
     *
     */
    @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {
        expListView  = (ExpandableListView) inflater.inflate(
                R.layout.fragment_navigation_campionati, container, false);
        expListView .setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                selectItem(position);
        mDrawerTitle= getActionBar().getTitle();
            }
        });
        /**
         * Definisce una nuova richiesta HTTP. Essa preleva i nomi ed i dati dei vari campionati,
         * riempiendo degli ArrayList che saranno poi usati per creare l'ExpandableListView
         */
        if(hasConnection(getActivity())) {
            HTTPRequest http=new HTTPRequest() {
            @Override
            protected void onPostExecute(String result) {
                //ArrayList di tutti i children che saranno inseriti nell'ExpandableListView
                ArrayList<String>A1M=new ArrayList();
                ArrayList<String>A1F=new ArrayList();
                ArrayList<String>A2M=new ArrayList();
                ArrayList<String>A2F=new ArrayList();
                ArrayList<String>B=new ArrayList();
                ArrayList<String>U21M=new ArrayList();
                ArrayList<String>U19F=new ArrayList();
                ArrayList<String>U17M=new ArrayList();
                ArrayList<String>U16F=new ArrayList();
                ArrayList<String>U14M=new ArrayList();
                ArrayList<String>U14F=new ArrayList();
                ArrayList<String>U12X=new ArrayList();
                super.onPostExecute(result);
                try {
                    //Formatta il risultato in un JSONArray
                    JSONArray dati = new JSONArray(result);
                    Log.i("INFO",result);
                    String categoria;   //Categoria del campionato
                    String genere;     //Genere (Maschile,Femminile,Misto)
                    String girone;     //Girone del campionato
                    String idcampionato;
                    for(int i=0;i<dati.length();i++)
                    {
                        JSONObject jsonobject = dati.getJSONObject(i);
                        categoria=jsonobject.getString("Categoria");
                        genere= jsonobject.getString("Genere");
                        girone= jsonobject.getString("Girone");
                        idcampionato= jsonobject.getString("IDCampionato");
                        switch (categoria){
                            case "A1":
                                if(genere.equals("Maschile")) {
                                    A1M.add(idcampionato+" Serie " + categoria + " " + genere + " " + girone);
                                }
                                else {
                                    A1F.add(idcampionato+" Serie " + categoria + " " + genere + " " + girone);
                                }
                                break;
                            case "A2":
                                if(genere.equals("Maschile")) {
                                    A2M.add(idcampionato+" Serie " +categoria + " " + genere + " " + girone);
                                }
                                else {
                                    A2F.add(idcampionato+" Serie " +categoria + " " + genere + " " + girone);
                                }
                                break;
                            case "B":
                                B.add(idcampionato+" Serie " +categoria + " " + genere + " "+girone);
                                break;
                            case "UNDER 21":
                                U21M.add(categoria + " " + genere + " "+girone);
                                break;
                            case "UNDER 19":
                                U19F.add(categoria + " " + genere + " "+girone);
                                break;
                            case "UNDER 17":
                                U17M.add(categoria + " " + genere + " "+girone);
                                break;
                            case "UNDER 16":
                                U16F.add(categoria + " " + genere + " "+girone);
                                break;
                            case "UNDER 14":
                                if(genere.equals("Maschile")) {
                                    U14M.add(categoria + " " + genere + " " + girone);
                                }
                                else {
                                    U14F.add(categoria + " " + genere + " " + girone);
                                }
                                break;
                            case "UNDER 12":
                                U12X.add(categoria + " " + genere + " "+girone);
                                break;
                        }
                        setChildGroupData(A1M, A1F, A2M, A2F, B, U21M, U19F, U17M, U16F, U14M
                                , U14F, U12X);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            @Override
            protected String doInBackground(String... params) {
                return super.doInBackground(params);
            }
        };
        //Effettua richiesta HTTP al WS

            http.execute(wsURL, "0", "mostraCampionati");
            //Crea un adapter per inserire gli ArrayList nell'ExpandableListView
            Log.i("INFO", String.valueOf(listDataChild.size()));
            expandableListAdapter = new MyExpandableListAdapter(getActivity().getBaseContext(), listDataHeader, listDataChild);
            //Sets the adapter for ExpandableList
            expListView.setAdapter(expandableListAdapter);
            //Sets the OnClickListener for childrens of the list
            expListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
                @Override
                public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                    String child = (String) parent.getExpandableListAdapter().getChild(groupPosition, childPosition);
                    String[] parti = child.split(" ");
                    key = Integer.parseInt(parti[0]);   //gets the key of tuple which is the first part of the string
                    //gets Fragment Manager
                    FragmentManager fragmentManager = getFragmentManager();
                    //starts the transaction
                    android.support.v4.app.FragmentTransaction ft = fragmentManager.beginTransaction();
                    ft.replace(R.id.viewpager, PagePartite.newInstance(key));   //first page
                    ft.replace(R.id.viewpager, PageClassifica.newInstance(key));    //second page
                    ft.replace(R.id.viewpager, PageStatistiche.newInstance(key));
                    ft.addToBackStack(null);
                    ft.commit();
                    mDrawerTitle = (child);
                    return true;
                }
            });
        }
        else
            Toast.makeText(getActivity(),"Connessione Internet assente",Toast.LENGTH_LONG).show();
        return expListView ;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mCallbacks = (NavigationDrawerCallbacks) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException("Activity must implement NavigationDrawerCallbacks.");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mCallbacks = null;
    }


    /**
     * Per the navigation drawer design guidelines, updates the action bar to show the global app
     * 'context', rather than just what's in the current screen.
     */
    private void showGlobalContextActionBar() {
        ActionBar actionBar = getActionBar();
        actionBar.setDisplayShowTitleEnabled(true);
    }

    private ActionBar getActionBar() {
        return ((ActionBarActivity) getActivity()).getSupportActionBar();
    }


    /**
     * Funzione che riempie l'HashMap ListDataChild con i dati ricevuti tramite richiesta HTTP.
     * @param par   ArrayList contenente i dati per ogni campionato
     */
    protected void setChildGroupData(ArrayList<String> ... par){
        //inserisce i dati dei Children e dei parent in un HashMap
        listDataChild.put(listDataHeader.get(0), par[0]);
        listDataChild.put(listDataHeader.get(1),par[1]);
        listDataChild.put(listDataHeader.get(2),par[2]);
        listDataChild.put(listDataHeader.get(3),par[3]);
        listDataChild.put(listDataHeader.get(4),par[4]);
        listDataChild.put(listDataHeader.get(5),par[5]);
        listDataChild.put(listDataHeader.get(6),par[6]);
        listDataChild.put(listDataHeader.get(7),par[7]);
        listDataChild.put(listDataHeader.get(8),par[8]);
        listDataChild.put(listDataHeader.get(9),par[9]);
        listDataChild.put(listDataHeader.get(10),par[10]);
        listDataChild.put(listDataHeader.get(11),par[11]);
    }

    /**
     * Lista che inserisce i titoli dei campionati all'interno di una HashMap
     */
    private void prepareHeaderData() {
        listDataHeader = new ArrayList<String>();
        listDataChild = new HashMap<String, List<String>>();
        //Titoli delle sezioni
        listDataHeader.add("Serie A1 Maschile");
        listDataHeader.add("Serie A1 Femminile");
        listDataHeader.add("Serie A2 Maschile");
        listDataHeader.add("Serie A2 Femminile");
        listDataHeader.add("Serie B Maschile");
        listDataHeader.add("Under 21 Maschile");
        listDataHeader.add("Under 19 Femminile");
        listDataHeader.add("Under 17 Maschile");
        listDataHeader.add("Under 16 Femminile");
        listDataHeader.add("Under 14 Maschile");
        listDataHeader.add("Under 14 Femminile");
        listDataHeader.add("Under 12 Mista");
    }

    /**
     * Callbacks interface that all activities using this fragment must implement.
     */
    public static interface NavigationDrawerCallbacks {
        /**
         * Called when an item in the navigation drawer is selected.
         */
        void onNavigationDrawerItemSelected(int position);
    }

First Fragment

package com.dcdeveloper.fihresults;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ProgressBar;
import android.widget.Spinner;
import android.widget.Toast;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;


/**
 * Fragment contenente le partite del campionato,disposte in giornate
 * Use the {@link PagePartite#newInstance} factory method to
 * create an instance of this fragment.
 */
// In this case, the fragment displays simple text based on the page
public class PagePartite extends Fragment implements AdapterView.OnItemSelectedListener{
/** View del frammento*/
protected View view;

private int mPage;
/**URL del WEB Service a cui effettuare richieste HTTP per ottenere i risultati delle partite*/
private String wsURL;
/**ID del campionato scelto*/
private static int idcampionato;
/**Layout che consente l'aggiornamento della pagina tramite swipe verticale*/
SwipeRefreshLayout mSwipeRefreshLayout;
/**Barra di progresso mostrata quando c'e una attesa nel caricamento dei dati*/
ProgressBar progressBar;
/**Spinner per scegliere la giornata del campionato di cui visualizzare le partite*/
Spinner spinner;
/**RecyclerView contenente le Card delle partite*/
RecyclerView recyclerList;
/**Giornata del campionato scelta*/
private int giornata;

/**
 * Inizializza il fragment con il campionato scelto.
 * @param IDCampionato  Il campionato scelto
 * @return  Fragment il fragment PagePartite
 */
public static Fragment newInstance(int IDCampionato) {
    PagePartite fragment = new PagePartite();
    idcampionato=IDCampionato;
    return fragment;
}

/**
 * Costruttore vuoto richiesto
 */
public PagePartite(){
    //required empty public constructor
}

/**
 * Funzione che inizializza i dati del Fragment
 * @param savedInstanceState
 */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

/**
 * Funzione che crea la grafica del Fragment definito nella funzione newIstance.Inizializza la RecyclerView con le View delle Card, lo SwipeRefreshLayout
 * @param inflater  Layout utilizzato per creare la grafica
 * @param container Container del Fragment
 * @param savedInstanceState
 * @return  View rappresentante il fragment
 */
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    //inflates the view inside ViewPager
    view = inflater.inflate(R.layout.fragment_partite, container, false);
    mSwipeRefreshLayout = (SwipeRefreshLayout) view.findViewById(R.id.partite_swipe_refresh_layout);
    mSwipeRefreshLayout.setColorSchemeResources(R.color.colore_sfondo_menu, R.color.indicator_color, R.color.colore_menu);
    mSwipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            refresh();
        }
    });
    giornata=1;

    spinner = (Spinner) view.findViewById(R.id.spinner);
    //adding recyclerList and setting its layout
    recyclerList = (RecyclerView) view.findViewById(R.id.cardList);
    recyclerList.setHasFixedSize(true);
    LinearLayoutManager layout = new LinearLayoutManager(view.getContext());
    layout.setOrientation(LinearLayoutManager.VERTICAL);
    recyclerList.setLayoutManager(layout);

    getGiornate();
    getPartite();
    return view;
}

/**
 * Funzione che riceve i risultati delle partite dopo aver effettuato una Richiesta HTTP,e li formatta all'interno di Card
 */
public void getPartite(){
    wsURL = "http://fihresults.altervista.org/WebServiceFihResults/service.php";
    if(hasConnection(view.getContext())) {
    HTTPRequest http=new HTTPRequest() {

        @Override
        protected void onPreExecute() {
            mSwipeRefreshLayout.setRefreshing(true);
            super.onPreExecute();
        }
        @Override
        protected String doInBackground(String... params) {
            return super.doInBackground(params);
        }

        @Override
        protected void onPostExecute(String result) {
            mSwipeRefreshLayout.setRefreshing(false);
            super.onPostExecute(result);
            Log.i("INFO getPartite", result);
            JSONArray dati = null;
            ArrayList partite = new ArrayList();
            try {
                dati = new JSONArray(result);
                for(int i=0;i<dati.length();i++) {
                    JSONObject jsonobject = dati.getJSONObject(i);
                    partite.add(new Partita(jsonobject));
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
            CardAdapter cardadapt = new CardAdapter(0,partite);
            recyclerList.setAdapter(cardadapt);
        }
    };

        http.execute(wsURL, "4", "mostraPartite", "IDCampionato", String.valueOf(idcampionato), "NumGiornata", String.valueOf(giornata));
    }
    else
        Toast.makeText(view.getContext(),"Connessione Internet assente",Toast.LENGTH_LONG).show();
}

/**
 * Funzione che effettua una richiesta HTTP per ricevere il numero di giornate del campionato,quindi inserisce tali dati all'interno dello Spinner
 */
public void getGiornate() {
    Log.i("INFO PagePartite", "ESEGUO getGiornate()");
    wsURL = "http://fihresults.altervista.org/WebServiceFihResults/service.php";
    if(hasConnection(view.getContext())) {
    HTTPRequest http=new HTTPRequest() {

        @Override
        protected void onPreExecute() {
            if(!mSwipeRefreshLayout.isRefreshing())
                mSwipeRefreshLayout.setRefreshing(true);
            super.onPreExecute();
        }

        @Override
        protected String doInBackground(String... params) {
            return super.doInBackground(params);
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            Log.i("INFO getGiornate",result);
            int numgiornate;
            ArrayList<String> giornate = new ArrayList();
            JSONArray dati = null;
            try {
                dati = new JSONArray(result);
                JSONObject jsonobject = dati.getJSONObject(0);
                numgiornate= jsonobject.getInt("NumGiornate");
                for(int i=1;i<=numgiornate;i++) {
                    String riga = "Giornata "+i;
                    giornate.add(riga);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            final ArrayAdapter<String> adapter = new ArrayAdapter<String>(view.getContext(),
                    android.R.layout.simple_list_item_1,giornate);
            spinner.setAdapter(adapter);
        }
    };

        http.execute(wsURL, "2", "getMaxGiornate", "IDCampionato", String.valueOf(idcampionato));
        spinner.setOnItemSelectedListener(this);
    }
    else
        Toast.makeText(view.getContext(),"Connessione Internet assente",Toast.LENGTH_LONG).show();
}

/**
 * Funzione che cambia i dati a seconda della giornata selezionata all'interno dello spinner
 * @param parent    Parent dello Spinner
 * @param view  View
 * @param position  Posizione selezionata all'interno dello spinner
 * @param id
 */
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    giornata=position+1;
    getPartite();
}

/**
 * Funzione che effettua il refresh dei dati della pagina
 */
public void refresh(){
    getGiornate();
    getPartite();
}
}

EDIT:

FragmentPagerAdapter

package com.dcdeveloper.fihresults;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.util.Log;
import android.view.View;

/**
 * Adapter per l'inserimento del frammento in un ViewPager.
 * Settato per contenere tre pagine, "Partite","Classifica" e "Statistiche"
 * Created by Dario on 06/06/2015.
 *
 */
public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
    final int PAGE_COUNT = 3;
    private String tabTitles[] = new String[] { "Partite", "Classifica", "Statistiche" };

    public MyFragmentPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    protected int idcampionato=1;  //default value
    @Override
    public int getCount() {
        return PAGE_COUNT;
    }

    /**
     * Funzione richiamata quando un Fragment non è inizializzato,come all'avvio dell'applicazione.Restituisce il Fragment creato.
     * @param position  Posizione in cui creare il Fragment
     * @return  Fragment appena creato ed inserito nell'Adapter
     */
    @Override
    public Fragment getItem(int position) {
        Fragment fragment=null;
        Log.i("MyFragmentPagerAdapter "+(String)getPageTitle(position),Integer.toString(position));
        switch(position) {
            //when created,cards will get the default value (idcampionato=1)
            case 0:
                fragment = PagePartite.newInstance(idcampionato);
                break;
            case 1:
                fragment = PageClassifica.newInstance(idcampionato);
                break;
            case 2:
                fragment = PageStatistiche.newInstance(idcampionato);
                break;
        }
        return fragment;
    }

    /**
     * Ritorna il titolo della pagina corrente
     * @param position  posizione corrente
     * @return  Charsequence che rappresenta il titolo
     */
    @Override
    public CharSequence getPageTitle(int position) {
        // Generate title based on item position
        return tabTitles[position];
    }

}

Answer 1

What I am going to show you is a very basic way to update ViewPager fragments by replacing the existing fragments with new instances every time the data changes.

This is the formula:

• Allow the FragmentPagerAdapter to get some updated data. In your case, you have an int value called "key" that gets updated when the user selects an item from the nav drawer. We are going to put a method on your FragmentPagerAdapter that will take a key value argument and start the update.
• Implement getItemPosition() on the FragmentPagerAdapter to return POSITION_NONE. This is what will tell the ViewPager that the current fragment is out of date and needs to be replaced with another fragment.
• In the getItem() method of the adapter, use the current key value when instantiating the new fragment. (You already have this part.)

This is what I would suggest for code changes:

1. Modify your Activity so that you have a reference to your FragmentPagerAdapter instance.

   private MyFragmentPagerAdapter mAdapter;
   

2. In your Activity, make sure your ViewPager is set up with your FragmentPagerAdapter. (You didn't post your Activity code, so just making sure you didn't miss this.) This should probably happen in onCreate().

   mAdapter = new MyFragmentPagerAdapter();
   ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
   

3. Add a method to your Activity to accept the key value from your nav drawer and pass it on to the adapter (we'll handle the adapter in a minute):

   public void select(int key) {
       mAdapter.setKey(key);
   }
   

4. Remove this FragmentTransaction code from your nav drawer onChildClick():

               //gets Fragment Manager
               FragmentManager fragmentManager = getFragmentManager();
               //starts the transaction
               android.support.v4.app.FragmentTransaction ft = fragmentManager.beginTransaction();
               ft.replace(R.id.viewpager, PagePartite.newInstance(key));   //first page
               ft.replace(R.id.viewpager, PageClassifica.newInstance(key));    //second page
               ft.replace(R.id.viewpager, PageStatistiche.newInstance(key));
               ft.addToBackStack(null);
               ft.commit();
   

   Your MyFragmentPagerAdapter is going to do all this fragment management for you. So replace that code with:

   ((MainActivity) getActivity()).select(key);
   

   (I don't know what your activity is called so I just used MainActivity for example.)

5. Override & implement getItemPosition() on your FragmentPagerAdapter so that it always returns POSITION_NONE:

   public int getItemPosition(Object object) {
       return POSITION_NONE;
   }
   

   You have to override this method because the base class method just returns POSITION_UNCHANGED, which results in getItem() never being called.

6. Finally, add the method to get the key value on the FragmentPagerAdapter. You already have a variable for the key so you can just use that to store the value:

   public void setKey(int key) {
       idcampionato = key;
       notifyDataSetChanged();
   }
   

So here is the sequence of events:

• User selects item from nav drawer.
• onChildClick() calls Activity.select() with value.
• select() calls setKey() on the adapter.
• adapter stores key value and calls notifyDataSetChanged().
• ViewPager notices adapter has changed and starts by calling adapter's getCount() to see if the number of fragments has changed.
• ViewPager calls getItemPosition() on each page position. POSITION_NONE is returned, which tells the ViewPager that the fragment at that page needs to be removed and replaced with a new fragment.
• ViewPager then calls getItem() on each page position. This will call the newInstance method of the fragment. Since your idcampionato value has been updated, the fragment is created with the new key.
• ViewPager displays the new fragment with the updated data.

This is not as elegant as the method I initially suggested, which is to create the fragments only once, then have a custom method on the fragment to update the key and refresh the fragment view. But that method would have required a lot more code changes for you, so I decided to go with the simpler solution.