Android - Fragment not attached to activity

Question

I have an activity which loads a fragment but when I press back button on the fragment it shows the error :-

"java.lang.IllegalStateException: Fragment ProductFragment{c46ba8a} not attached to Activity"

Code is below:-

Product Fragment:

public class ProductFragment extends Fragment implements TabLayout.OnTabSelectedListener, ViewPager.OnPageChangeListener {
    private static final String PRODUCT_DATA = "product_data";
    private TabLayout tabLayout;
    private ViewPager viewPager;
    NestedScrollView nestedScrollView;

    //RecyclerView listView;
    //ImageView ivHeader;
    ProgressDialog pd;
    Bundle bundle;
    ViewPager viewPager1;
    private LinearLayout pager_indicator;
    public String DATA = "data";
    public String PRODUCTS = "products";
    //public String SPRODUCTS = "sproducts";
    public String ID = "id";
    public String NAME = "productName";
    public String IMAGEURL = "productImg1";
    public String DESCRIPTION = "description";
    public String PRICE = "price";
    public String DELIVERYTYPE = "deliverytype";
    //String url = "https://chiraggohil.000webhostapp.com/product.php";
    String url = "http://www.thinkdream.in/lunchbox2/product_api/getProductList";
    String sliderImageUrl = "http://www.thinkdream.in/lunchbox2/assets/images/product/2.png";

    ArrayList<Product> list = new ArrayList<>();
    ArrayList<Product> sliderImagesList = new ArrayList<>();
    private int dotsCount = 0;
    private ImageView[] dots;
    private static int CURRENT_PAGE = 0;
    ViewPagerSliderAdapter viewPagerSliderAdapter;

    ConnectivityManager cm;
    NetworkInfo activeNetwork;
    boolean isConnected;

    //private boolean load = false;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        final View v = inflater.inflate(R.layout.fragment_product, container, false);
        viewPager1 = (ViewPager) v.findViewById(R.id.viewpager);
        //listView = (RecyclerView) v.findViewById(R.id.gvProducts);
        nestedScrollView = (NestedScrollView) v.findViewById(R.id.nestedSV);
        pager_indicator = (LinearLayout) v.findViewById(R.id.viewPagerCountDots);

        //nestedScrollView.setFillViewport(true);
        //ivHeader = (ImageView) v.findViewById(R.id.ivHeader);
        bundle = new Bundle();
        tabLayout = (TabLayout) v.findViewById(R.id.tabLayout);
        viewPager = (ViewPager) v.findViewById(R.id.pager);

        viewPagerSliderAdapter = new ViewPagerSliderAdapter(getActivity(), sliderImagesList);

        cm = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
        activeNetwork = cm.getActiveNetworkInfo();
        isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();

        if (savedInstanceState != null) {
            sliderImagesList = savedInstanceState.getParcelableArrayList(PRODUCT_DATA);
            viewPager1.setAdapter(viewPagerSliderAdapter);
            viewPagerSliderAdapter.notifyDataSetChanged();
        } else {
            if (isConnected) {
                new GetUrlData(getActivity()).execute();
            } else {
                Toast.makeText(getActivity(), "You are not connected to the internet!", Toast.LENGTH_SHORT).show();
            }
        }

        tabLayout.addTab(tabLayout.newTab().setText("Pizza"));
        tabLayout.addTab(tabLayout.newTab().setText("Sandwich"));
        tabLayout.addTab(tabLayout.newTab().setText("Burger"));
        Pager adapter = new Pager(getChildFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(this);

        viewPager1.addOnPageChangeListener(this);
        return v;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putParcelableArrayList(PRODUCT_DATA, sliderImagesList);
    }

    @Override
    public void onResume() {
        super.onResume();
        pager_indicator.removeAllViews();
        //Picasso.with(getActivity()).load(sliderImageUrl).into(ivHeader);
    }

    @Override
    public void onTabSelected(TabLayout.Tab tab) {
        viewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(TabLayout.Tab tab) {

    }

    @Override
    public void onTabReselected(TabLayout.Tab tab) {

    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    @Override
    public void onPageSelected(int position) {
        for (int i = 0; i < dotsCount; i++) {
            dots[i].setImageDrawable(getResources().getDrawable(R.drawable.nonselecteditem_dot));
        }
        if (position >= dotsCount) {
            dots[0].setImageDrawable(getResources().getDrawable(R.drawable.selecteditem_dot));
        } else {
            dots[position].setImageDrawable(getResources().getDrawable(R.drawable.selecteditem_dot));
        }
    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }

    private class GetUrlData extends AsyncTask<Void, Void, Void> {

        GetUrlData(Context context) {
            pd = new MyCustomProgressDialog(context, R.style.NewDialog);
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pd.setCancelable(false);
            pd.show();
        }

        @Override
        protected Void doInBackground(Void... voids) {
            ServiceHandler sh = new ServiceHandler();
            String result = sh.Getdata(url);
            //list.clear();
            sliderImagesList.clear();

            if (result != null) {
                try {
                    list.clear();
                    JSONObject jsonObject = new JSONObject(result);
                    JSONArray jsonArray = jsonObject.getJSONArray(DATA);

                    //JSONArray jsonArray = jsonObject1.getJSONArray(PRODUCTS);

                    for (int i = 0; i < jsonArray.length(); i++) {
                        JSONObject jsonObject2 = jsonArray.getJSONObject(i);
                        String id = jsonObject2.getString(ID);
                        String name = jsonObject2.getString(NAME);
                        String imgpath = jsonObject2.getString(IMAGEURL);
                        String desc = jsonObject2.getString(DESCRIPTION);
                        String price = jsonObject2.getString(PRICE);
                        //String deliverytype = jsonObject2.getString(DELIVERYTYPE);

                        Product product = new Product();
                        product.setId(id);
                        product.setProductName(name);
                        product.setProductImage(imgpath);
                        product.setProductDescription(desc);
                        product.setProductPrice(price);
                        //list.add(product);
                        sliderImagesList.add(product);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            pd.dismiss();
            // Picasso.with(getActivity()).load(sliderImageUrl).into(ivHeader);
            if(isAdded()) {
            viewPagerSliderAdapter = new ViewPagerSliderAdapter(getActivity(), sliderImagesList);
            Log.e("slider",sliderImagesList.toString());
            viewPager1.setAdapter(viewPagerSliderAdapter);
            viewPagerSliderAdapter.notifyDataSetChanged();
            slider();
            setUiPageViewController();
            }else {
                Log.e("not added","not added");
            }
        }

    }

    private void slider() {
        int NUM_PAGES = sliderImagesList.size();
        final android.os.Handler handler = new android.os.Handler();
        final Runnable runnable = new Runnable() {
            @Override
            public void run() {
                CURRENT_PAGE = viewPager1.getCurrentItem();
                if (CURRENT_PAGE == 2) {
                    CURRENT_PAGE = -1;
                }
                viewPager1.setCurrentItem(CURRENT_PAGE + 1, true);
            }
        };
        Timer swipeTimer = new Timer();
        swipeTimer.schedule(new TimerTask() {
            @Override
            public void run() {
                handler.post(runnable);
            }
        }, 100, 4000);
    }

    private void setUiPageViewController() {
        dotsCount = 3;
        dots = new ImageView[dotsCount];

        for (int i = 0; i < dotsCount; i++) {
            dots[i] = new ImageView(getActivity());
            dots[i].setImageDrawable(getResources().getDrawable(R.drawable.nonselecteditem_dot));

            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.WRAP_CONTENT,
                    LinearLayout.LayoutParams.WRAP_CONTENT
            );

            params.setMargins(4, 0, 4, 0);

            pager_indicator.addView(dots[i], params);
        }
        dots[0].setImageDrawable(getResources().getDrawable(R.drawable.selecteditem_dot));
    }


}

I don't know where I am wrong. I have searched for the error and even tried the solution from the link below:
Fragment MyFragment not attached to Activity
I ask questions on SO but I don't get response/answers. May be there is a small mistake, grammatical/formating problem, or a duplicate question but there is a possibility of my case that is different then others.
So please help and response.
Thanks.
--Edited--
HomeActivity :

public class HomeActivity extends AppCompatActivity implements View.OnClickListener {
    DrawerLayout drawerLayout;
    NavigationView navigationView;
    Toolbar toolbar;
    TextView tvActionTitle;
    SessionManager sessionManager;
    GPSTracker gps;
    int i = 0;
    private FrameLayout redCircle;
    private TextView countTextView;
    int cartcount = 0;
    Menu menu;
    LunchBoxDB lunchBoxDB;
    private String uid;
    SharedPreferences pref;
    private int totalquantity = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        navigationView = (NavigationView) findViewById(R.id.navigation);
        tvActionTitle = (TextView) findViewById(R.id.tvActionTitle);

        Typeface custom_font = Typeface.createFromAsset(getAssets(), "fonts/Quicksand_Bold_Oblique.otf");
        tvActionTitle.setTypeface(custom_font);

        setSupportActionBar(toolbar);
        //getSupportActionBar().setDisplayShowTitleEnabled(false);
        lunchBoxDB = new LunchBoxDB(this);
        pref = getSharedPreferences("loginPref", Context.MODE_PRIVATE);
        uid = pref.getString("id", null);

        ProductFragment pf = new ProductFragment();
        getFragmentManager().beginTransaction().replace(R.id.content_frame, pf).commit();

        sessionManager = new SessionManager(this);
        toolbar.setNavigationIcon(R.mipmap.ic_menu_white_24dp);
        toolbar.setNavigationOnClickListener(this);

        navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem item) {
                Fragment frag = null;
                int itemId = item.getItemId();
                if (itemId == R.id.nav_home) {
                    drawerLayout.closeDrawers();
                    Intent i = new Intent(HomeActivity.this, HomeActivity.class);
                    startActivity(i);
                    HomeActivity.this.finish();
                } else if (itemId == R.id.nav_profile) {
                    frag = new AccountFragment();
                    getFragmentManager().beginTransaction().replace(R.id.content_frame, frag).addToBackStack("Account").commit();
                    drawerLayout.closeDrawers();
                } else if (itemId == R.id.nav_order) {
                    drawerLayout.closeDrawers();
                    OrdersFragment of = new OrdersFragment();
                    getFragmentManager().beginTransaction().replace(R.id.content_frame, of).addToBackStack("Orders").commit();
                } else if (itemId == R.id.nav_store_locator) {
                    Intent i = new Intent(HomeActivity.this, LocationActivity.class);
                    startActivity(i);
                    drawerLayout.closeDrawers();
                } else if (itemId == R.id.nav_logout) {
                    drawerLayout.closeDrawers();
                    sessionManager.logoutUser();
                } else if (itemId == R.id.nav_help) {
                    drawerLayout.closeDrawers();
                    Intent i = new Intent(Intent.ACTION_DIAL);
                    i.setData(Uri.parse("tel:+918460765785"));
                    startActivity(i);
                } else if (itemId == R.id.nav_corpinquiry) {
                    drawerLayout.closeDrawers();
                    CorpInquiryFragment crpf = new CorpInquiryFragment();
                    getFragmentManager().beginTransaction().replace(R.id.content_frame, crpf).addToBackStack("CorpInquiry").commit();
                }
                return false;
            }
        });

    }

    private void setNavigationDrawer() {
        if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
            drawerLayout.closeDrawer(GravityCompat.START);
        } else {
            drawerLayout.openDrawer(GravityCompat.START);

        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.nav_drawer, menu);
        final MenuItem alertMenuItem = menu.findItem(R.id.shopping_bag);
        FrameLayout rootView = (FrameLayout) alertMenuItem.getActionView();

        redCircle = (FrameLayout) rootView.findViewById(R.id.view_alert_red_circle);
        countTextView = (TextView) rootView.findViewById(R.id.view_alert_count_textview);

        rootView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onOptionsItemSelected(alertMenuItem);
            }
        });
        badgeupdate();
        return super.onCreateOptionsMenu(menu);
    }

    void badgeupdate() {
        SQLiteDatabase db = lunchBoxDB.getReadableDatabase();
        String query = "select sum(quantity) from cart where uid = " + uid;
        Cursor c = db.rawQuery(query, null);
        if (c != null && c.moveToFirst()) {
            totalquantity = c.getInt(0);
        }
        c.close();
        cartcount = totalquantity;
        countTextView.setText(String.valueOf(cartcount));
        redCircle.setVisibility((cartcount > 0) ? VISIBLE : GONE);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.shopping_bag) {
            SharedPreferences pref = this.getSharedPreferences("couponPref", Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = pref.edit();
            editor.putString("discount", null);
            editor.apply();
            CartFragment cf = new CartFragment();
            getFragmentManager().beginTransaction().replace(R.id.content_frame, cf, "CartFragment").addToBackStack(null).commit();
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onBackPressed() {
        if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
            drawerLayout.closeDrawer(GravityCompat.START);
        }/*else if(i==0){
            Toast.makeText(this, "Press back again to exit!", Toast.LENGTH_SHORT).show();
            i=1;
        }*/ else {
            //i=0;
            super.onBackPressed();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        gps = new GPSTracker(this);
    }

    @Override
    public void onClick(View view) {
        setNavigationDrawer();
    }
}

Logcat error :

FATAL EXCEPTION: main Process: com.pisac.foodrestaurant, PID: 29700 java.lang.IllegalStateException: Fragment ProductFragment{13525074} not attached to Activity at android.app.Fragment.getResources(Fragment.java:800) at com.pisac.foodrestaurant.ProductFragment.onPageSelected(ProductFragment.java:149) at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1967) at android.support.v4.view.ViewPager.scrollToItem(ViewPager.java:685) at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:669) at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:630) at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:622) at com.pisac.foodrestaurant.ProductFragment$1.run(ProductFragment.java:244) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5910) at java.lang.reflect.Meth od.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200)

Answer 1

You have problem with the line

    pd.dismiss();

in onPostExecute of your GetUrlData . Put it inside if (isAdded ()) As per the answer of the question you reffered in your question. Your dialog uses the context of the activity.

EDIT

Add an if block in onPageSelected method that checks if Fragment if attached ie

@Override
public void onPageSelected(int position) {
    if(!isAdded ())
         return;

    for (int i = 0; i < dotsCount; i++) {
        dots[i].setImageDrawable(getResources().getDrawable(R.drawable.nonselecteditem_dot));
    }
    if (position >= dotsCount) {
        dots[0].setImageDrawable(getResources().getDrawable(R.drawable.selecteditem_dot));
    } else {
        dots[position].setImageDrawable(getResources().getDrawable(R.drawable.selecteditem_dot));
    }
}

Answer 2

Thanks for helping me.
I got the answer.
I added onStop in the ProductFragment code as below :

@Override
public void onStop() {
    viewPager1.setAdapter(null);
    super.onStop();
}  

and update the onResume :

@Override
public void onResume() {
    super.onResume();
    pager_indicator.removeAllViews();
    if(viewPagerSliderAdapter==null){
        new GetUrlData(getActivity()).execute();
    }
}

Thanks once again.