java - Recyclerviews in ViewPager

Question

I'm trying to get this working: I basically want two Recyclerviews in one ViewPager. I followed this Tutorial: http://android-java-development.blogspot.de/2012/05/system.html, but it doesn't seem to work. I looks like the view pager is empty and the recycler view doesn't show up.

Here's my layout code:

<android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/pager_refresh_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingTop="@dimen/tab_height">

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@color/accent"/>
    </android.support.v4.widget.SwipeRefreshLayout>

And my PageAdapter:

public class NewsPagerAdapter extends PagerAdapter {
    private Context context;
    private Vector<RecyclerView> recyclerViewList;
    private String[] titles;

    public NewsPagerAdapter(Context context, int titlesId) {
        this.context = context;
        this.recyclerViewList = new Vector<>();

        setTitles(titlesId);
    }

    public void add(RecyclerView recyclerView) {
        recyclerViewList.add(recyclerView);
    }

    public RecyclerView.Adapter getAdapterForViewAtIndex(int index) {
        return recyclerViewList.get(index).getAdapter();
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        container.addView(recyclerViewList.get(position),
                new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 100)
        );
        return container;
    }

    @Override
    public int getCount() {
        return recyclerViewList.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view.equals(object);
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View) object);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return titles[position];
    }

    public void setTitles(int titles) {
        this.titles = context.getResources().getStringArray(titles);
    }
}

And my onCreatView method:

GridLayoutManager layoutManager1 = new GridLayoutManager(getActivity(), getResources().getInteger(R.integer.news_column_count));

GridLayoutManager layoutManager2 = new GridLayoutManager(getActivity(), getResources().getInteger(R.integer.news_column_count));

RecyclerView listView1 = new RecyclerView(getActivity());
RecyclerView listView2 = new RecyclerView(getActivity());
listView1.setLayoutManager(layoutManager1);
listView2.setLayoutManager(layoutManager2);

NewsAdapter adapter1 = new NewsAdapter(getActivity(), null);
NewsAdapter adapter2 = new NewsAdapter(getActivity(), null);
adapter1.setOnItemClickListener(this);
adapter2.setOnItemClickListener(this);

listView1.setAdapter(adapter1);
listView2.setAdapter(adapter2);

newsPagerAdapter.add(listView1);
newsPagerAdapter.add(listView2);

newsViewPager.setAdapter(newsPagerAdapter);

Here I'm passing the cursor object to the adapter:

@Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        ((NewsAdapter) newsPagerAdapter.getAdapterForViewAtIndex(0)).swapCursor(data);
    }

Answer 1

You have to extend FragmentPagerAdapter or FragmentStatePagerAdapter in order to easily embed RecyclerView. If you are going to update your ViewPager contents during its lifecycle it is strictly recommended to use FragmentStatePagerAdapter

You will have to create additional fragment layout, containing RecyclerView.

If you wish to update your ViewPager with SwipeRefreshLayout, don't wrap it with SwipeRefreshLayout. Instead, you must have SwipeRefreshLayout inside fragment layout.

Therefore for your fragment you may get the following xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.SwipeRefreshLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/listRefresh"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v7.widget.RecyclerView
        android:id="@+id/categoryList"
        android:scrollbars="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</android.support.v4.widget.SwipeRefreshLayout>

And create additional Fragment class, which will inflate that layout and implement methods, that you will need to update refresh indicator status.

A bit old example is found here: http://developer.android.com/training/implementing-navigation/lateral.html

If you wish to connect your ViewPager with new support library TabLayout, it is easily one with:

tabLayout.setupWithViewPager(viewPager);

Finally, if you will update your "fragmented" ViewPager, don't try to reset the adapter, as fragments are managed not with adapter, but with FragmentManager. It is wiser to update content of corresponding RecyclerViews

public class MyFragmentedPagerAdapter extends FragmentStatePagerAdapter {
    private final TabLayout mTabLayout;
    private final SwipeRefreshLayout.OnRefreshListener mRefreshListener;
    private Vector<PriceListFragment> fragmentList;
    private Vector<String> titles;

    public MyFragmentedPagerAdapter(FragmentManager fm, MyComplexData data, OnCartActionListener listener, TabLayout tabLayout, SwipeRefreshLayout.OnRefreshListener refreshListener) {
        super(fm);
        mTabLayout = tabLayout;

        // external refresh listener, that will trigger an updateData() 
        mRefreshListener = refreshListener;

        fragmentList = new Vector<>();
        titles = new Vector<>();
        updateData(data);
    }

    public void updateData(MyComplexData data) {
        boolean updateTabs = false;
        boolean hasNewData = false;

        Vector<String> newTitles = new Vector<>();

        int position = 0;
        for(TabContents tabContents : data.getTabContents()) {

            if(tabContents.getListContents() == null)
                continue;
            hasNewData = true;
            boolean isNewFragment;

            MyFragment fragment;
            try {
                fragment = fragmentList.get(position);
                isNewFragment = false;
            } catch (ArrayIndexOutOfBoundsException e) {
                fragment = new MyFragment();
                isNewFragment = true;
            }
            // Update the data, title and hide update indicator of SwipeRefreshLayout
            fragment.setTabContents(tabContents);

            newTitles.add(tabContents.getName());

            if(isNewFragment) {
                fragment.setRefreshListener(mRefreshListener);
                fragmentList.add(fragment);
            }
            position++;
        }

        if(!hasNewData)
            return;

        // we need to decide, whether to update tabs
        if(titles.size() != newTitles.size()) {
            updateTabs = true;
        } else {
            for(position = 0; position < titles.size(); position++) {
                if(!titles.get(position).equals(newTitles.get(position))) {
                    updateTabs = true;
                    break;
                }
            }
        }

        titles = newTitles;
        notifyDataSetChanged();

        if(updateTabs)
            mTabLayout.setTabsFromPagerAdapter(this);
    }

    @Override
    public Fragment getItem(int position) {
        return fragmentList.get(position);
    }

    // You need to override this method as well
    @Override
    public int getItemPosition(Object object) {
        MyFragment fragment = (MyFragment) object;
        String title = (String) fragment.getTitle();
        int position = titles.indexOf(title);

        if (position >= 0) {
            return position;
        } else {
            return POSITION_NONE;
        }
    }

    @Override
    public int getCount() {
        return titles.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return fragmentList.get(position).getTitle();
    }
}

Your MyFragment class has to implement getTitle() method.