in viewPager's fragment, recyclerView adapter notifyDataSetChanged not works on first time

Question

I have fragment view pager in activity, that creates a number of pages of entered number before. In each fragment, i have recycler view that needs to update each time user moves to the relevant page. on resume() of each fragment I have getter of data from main activity.

What I am experiencing is while I'm going to next page first time it's not updated, but if after some page movements I would back to it, it is updated, with same resume() code.

I tried some delays after updating the data, it didn't help.

So if before updating data I would check every page it would work as I planned, but if the page was not created before (due to pager adapter) but I still use the same code for updating, it does not work.

I would be glad for some help, stacked on it for 2 days already.

Main Activity:

package com.slavafleer.tipcalculator02;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import com.slavafleer.tipcalculator02.recycler.PageHeaderAdapter;

import java.util.ArrayList;

public class ManualModeActivity extends AppCompatActivity implements
        PageHeaderAdapter.Callbacks, DinerFragment.Callbacks {

    private int mDinersAmount;
    private ViewPager mViewPagerDiners;
    private PageHeaderAdapter mHeaderAdapter;
    private DinersPagerAdapter mDinersPagerAdapter;
    private ArrayList<Order> mOrders;

    public ArrayList<Order> getOrders() {
        return mOrders;
    }

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

        mOrders = new ArrayList<>();

        // Get diners amount from previous activity
        Intent intent = getIntent();
        mDinersAmount = intent.getIntExtra(Constants.KEY_DINNERS_AMOUNT, 1);

        // Initialise PageHeader Recycler
        mHeaderAdapter = new PageHeaderAdapter(this, mDinersAmount, this);
        final RecyclerView recyclerPageHeader = (RecyclerView) findViewById(R.id.recyclerViewPagerHeader);
        final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
        recyclerPageHeader.setLayoutManager(linearLayoutManager);
        recyclerPageHeader.setAdapter(mHeaderAdapter);

        // Initialise ViewPager
        mViewPagerDiners = (ViewPager) findViewById(R.id.viewPagerDiners);
        FragmentManager fragmentManager = getSupportFragmentManager();
        mDinersPagerAdapter = new DinersPagerAdapter(fragmentManager, mDinersAmount);
        mViewPagerDiners.setAdapter(mDinersPagerAdapter);

        // ViewPager Listener - synchronise with headers recycler
        mViewPagerDiners.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {

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

            }

            // Gets position for selected page
            @Override
            public void onPageSelected(int position) {

                mHeaderAdapter.selectItem(position);
                linearLayoutManager.smoothScrollToPosition(recyclerPageHeader, null,position);
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

    // HeaderPage Adapter Callbacks
    // Scroll ViewPager by clicked Header
    @Override
    public void onItemClick(int position) {
        mViewPagerDiners.setCurrentItem(position, true);
    }

    // DinerFragment.OrderDialog.Callbacks
    // Send data to PagerAdapter that would sent to each fragment
    @Override
    public void onDialogAddClick(Order order) {

        Log.d("test", "onDialogAddClick");

        mOrders.add(order);
        mDinersPagerAdapter.updateOrders();
    }
}

PagerAdapter

package com.slavafleer.tipcalculator02;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;

import java.util.ArrayList;

/**
 * PagerAdapter for ManualModeActivity ViewPager
 */
public class DinersPagerAdapter extends FragmentPagerAdapter {

    private int mDinersAmount;
    private ArrayList<DinerFragment> mDinerFragments;

    public DinersPagerAdapter(FragmentManager fm, int dinersAmount) {
        super(fm);

        mDinersAmount = dinersAmount;
        mDinerFragments = new ArrayList<>();
    }

    @Override
    public Fragment getItem(int position) {

        // Insert diners amount to fragment
        Bundle bundle = new Bundle();
        bundle.putInt(Constants.KEY_DINNERS_AMOUNT, mDinersAmount);
        bundle.putInt(Constants.KEY_CURRENT_PAGE, position);
        DinerFragment dinerFragment = new DinerFragment();
        dinerFragment.setArguments(bundle);
        mDinerFragments.add(dinerFragment); // save fragments references

        return dinerFragment;
    }

    // Diners amount + All
    @Override
    public int getCount() {
        return mDinersAmount + 1;
    }

    // Update order list in each fragment of view pager
    public void updateOrders() {

        for(DinerFragment dinerFragment : mDinerFragments) {
            dinerFragment.onResume();
        }
    }
}

Fragment

package com.slavafleer.tipcalculator02;


import android.os.Bundle;
import android.support.v4.app.Fragment;
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.ImageView;

import com.slavafleer.tipcalculator02.recycler.OrdersAdapter;

import java.util.ArrayList;


/**
 * Diner Fragment Class
 */
public class DinerFragment extends Fragment implements OrderDialog.Callbacks {

    private ArrayList<Order> mOrders = new ArrayList<>();
    private RecyclerView mRecyclerViewOrders;
    private ImageView mImageViewAddOrderButton;
    private int mDinersAmount;
    private OrdersAdapter mOrdersAdapter;
    private int mDinerId;
    private Callbacks mCallbacks;

    public DinerFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        Log.d("test", "onCreateView");

        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_diner, container, false);

        mCallbacks = (Callbacks) inflater.getContext();

        // Get Diners Amount
        final Bundle bundle = getArguments();
        if(bundle != null) {
            mDinersAmount = bundle.getInt(Constants.KEY_DINNERS_AMOUNT);
            mDinerId = bundle.getInt(Constants.KEY_CURRENT_PAGE);

            Log.d("test", "onCreateView " + mDinerId);
        }

        mRecyclerViewOrders = (RecyclerView) view.findViewById(R.id.recyclerViewOrders);

        mOrdersAdapter = new OrdersAdapter(getActivity(), mOrders);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
        mRecyclerViewOrders.setLayoutManager(linearLayoutManager);
        mRecyclerViewOrders.setAdapter(mOrdersAdapter);

        // Due to the bug, we could use just listener and not OnClick in Fragment
        mImageViewAddOrderButton = (ImageView) view.findViewById(R.id.imageViewAddButton);
        mImageViewAddOrderButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ArrayList<Integer> currentPage = new ArrayList<>();
                currentPage.add(mDinerId);
                OrderDialog orderDialog = new OrderDialog(getActivity(),
                        mDinersAmount, currentPage, DinerFragment.this);
                orderDialog.show();
            }
        });

        return view;
    }

    @Override
    public void onResume() {
        super.onResume();

        Log.d("test", "onResume " + mDinerId);

        ManualModeActivity activity = (ManualModeActivity) getActivity();
        mOrders = activity.getOrders();

        for(Order order : mOrders) {
            Log.d("test", order.getPrice() + "");
        }

        int size = mOrders.size();
        mOrdersAdapter.notifyDataSetChanged();
        mRecyclerViewOrders.smoothScrollToPosition(size);
    }

    // Blank OrderDialog.Callbacks
    // used due to Implements for creation OrderDialog
    @Override
    public void onDialogAddClick(Order order) {

        mCallbacks.onDialogAddClick(order);
    }

    public interface Callbacks {

        void onDialogAddClick(Order order);
    }
}

Answer 1

ViewPager adapter creates 2 fragments at the same time. for instance when you're on page 0, it also creates page 1(lifecycle for page 1: OnCreate->OnCreateView->OnResume->OnPause->OnResume).When you swipe to page 1 only method that is being called is SetMenuVisibility. So in order to update data for page 1 is to call setMenuVisibilty inside of Fragment:

@Override
public void setMenuVisibility(boolean menuVisible) {
    super.setMenuVisibility(menuVisible);
    if(menuVisible && isResumed()){
            settingAdapter();
    }
}

So here inside of settingAdapter i reloaded data. so far,it's the best trick i made toward fragments with recyclerviews inside viewpager. But still there are few milliseconds delay for populating fragment with new data))) I hope this will help you

Answer 2

Finally what I did is replacing mOrdersAdapter.notifyDataSetChanged() on recreating the adapter. I understand that is not a very smart solution but visually it does work as I needed.

I would not mark it as answer cause I still want to know why it acts like I wrote before.

Thanks again.

//        mOrdersAdapter.notifyDataSetChanged();
        mOrdersAdapter = new OrdersAdapter(getActivity(), mOrders);
        mRecyclerViewOrders.setAdapter(mOrdersAdapter);

Answer 3

Instead of using onResume use the onPageSelected method and used the passed fragment for context to call the updating method in the fragment.