RecyclerView: No adapter is attached; skipping layout - error inside of Fragment

Issue

I have MainActivity that holds three tabs. In each tab I'm displaying data taken from SQLite db as list using RecyclerView.

When I first launch app the data is shown properly. After I return to previously opened tab the data is not there.

The problem started to appear after I have implemented following:

1. Check if adapter is null.
2. If yes, create adapter instance and fill it with data.
3. If no, just update the data inside of adapter and call notifyDataSetChanged()

This idea was working in other project where I had to do same with Activity. In this case I have fragment. I have just get to know that Fragment has different lifecycle behavior.

How I can solve this problem?

One of the tabs class:

public class AllTabView extends Fragment {

Context ourContext;

RecyclerView mList;
AllAdapter adapter;
RecyclerView.LayoutManager layoutManager;
TextView mEmptyText;

long movedItem, draggedItem;

ArrayList<ArrayList<String>> mDays;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v1 = inflater.inflate(R.layout.list_view_content, container, false);

    mList = (RecyclerView) v1.findViewById(R.id.recycler_view);
    mEmptyText = (TextView) v1.findViewById(R.id.empty_text);
    ourContext = getContext();

    layoutManager = new LinearLayoutManager(ourContext);
    mList.setLayoutManager(layoutManager);
    RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();
    mList.setItemAnimator(itemAnimator);

    return v1;
}

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

    if (mDays.size() == 0) {
        mList.setVisibility(View.GONE);
        mEmptyText.setVisibility(View.VISIBLE);
    } else {
        mList.setVisibility(View.VISIBLE);
        mEmptyText.setVisibility(View.GONE);

        if(adapter == null) {
            Log.v(TAG, "adapter null");
            adapter = new AllAdapter(ourContext, mDays);
        }
        else {
            Log.v(TAG, "notify");
            adapter.updateData(mDays);
        }

        mList.setAdapter(adapter);
    }
}

public void getDays() {
    DaysDatabase info = new DaysDatabase(ourContext);
    info.open();
    mDays = info.getData();
    info.close();
}

public void setAdapter() {
    adapter = new AllAdapter(ourContext, mDays);
    mList.setAdapter(adapter);
}
}

MainActivity that holds fragments:

public class MainActivity extends AppCompatActivity {

FragmentTabHost mFragmentTabHost;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    mFragmentTabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);
    mFragmentTabHost.setup(MainActivity.this, getSupportFragmentManager(), android.R.id.tabcontent);

    String tag1 = "all";
    String tag2 = "since";
    String tag3 = "until";

    final View tabView1 = createTabView(MainActivity.this, "All");
    final View tabView2 = createTabView(MainActivity.this, "Since");
    final View tabView3 = createTabView(MainActivity.this, "Until");

    mFragmentTabHost.addTab(mFragmentTabHost.newTabSpec(tag1).setIndicator(tabView1).setContent(new FragmentTabHost.TabContentFactory() {
        public View createTabContent(String tag1) {
            return tabView1;
        }
    }), AllTabView.class, null);
    mFragmentTabHost.addTab(mFragmentTabHost.newTabSpec(tag2).setIndicator(tabView2).setContent(new FragmentTabHost.TabContentFactory() {
        public View createTabContent(String tag2) {
            return tabView2;
        }
    }), SinceTabView.class, null);
    mFragmentTabHost.addTab(mFragmentTabHost.newTabSpec(tag3).setIndicator(tabView3).setContent(new FragmentTabHost.TabContentFactory() {
        public View createTabContent(String tag1) {
            return tabView3;
        }
    }), UntilTabView.class, null);

    mFragmentTabHost.getTabWidget().setDividerDrawable(R.drawable.tab_divider);

}

private static View createTabView(final Context context, final String text) {
    View view = LayoutInflater.from(context).inflate(R.layout.tabs_bg, null);
    TextView tv = (TextView) view.findViewById(R.id.tabsText);
    tv.setText(text);
    return view;
}

Solution

I have edited your code. Please take a look.

public class AllTabView extends Fragment {

Context ourContext;

RecyclerView mList;
AllAdapter adapter;
RecyclerView.LayoutManager layoutManager;
TextView mEmptyText;

long movedItem, draggedItem;

ArrayList<ArrayList<String>> mDays = new ArrayList<>();

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v1 = inflater.inflate(R.layout.list_view_content, container, false);

    mList = (RecyclerView) v1.findViewById(R.id.recycler_view);
    mEmptyText = (TextView) v1.findViewById(R.id.empty_text);
    ourContext = getContext();
    layoutManager = new LinearLayoutManager(ourContext);
    mList.setLayoutManager(layoutManager);
    getDays();
    RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();
    mList.setItemAnimator(itemAnimator);
    adapter = new AllAdapter(ourContext, mDays);
    mList.setAdapter(adapter);
    return v1;
}

@Override
public void onResume() {
    super.onResume();
    getDays();
    if (mDays.size() == 0) {
        mList.setVisibility(View.GONE);
        mEmptyText.setVisibility(View.VISIBLE);
    } else {
        mList.setVisibility(View.VISIBLE);
        mEmptyText.setVisibility(View.GONE);
    }
}

public void getDays() {
    DaysDatabase info = new DaysDatabase(ourContext);
    info.open();
    mDays.clear();
    mDays.addAll(info.getData());
    if (adapter != null)
        adapter.notifyDataSetChanged();
    info.close();
}
}

Answered By - Aman Jain