Bundle being passed to Fragment is null?

Question

I'm working on a tab layout with several fragments which need to have an object passed to them from a previous activity so they can populate their lists, and I'm running into an error when I try to retrieve that object from the bundle. I have previously passed this same object between other activities with no issue. I made the object Parcelable so I can add it to a bundle and pass it as an argument. Here is the code for the adapter class that spits out the Fragments used in the tab layout:

package edu.uml.android.adventurersarchive;

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

import edu.uml.android.adventurersarchive.character.CharacterInfo;

public class SpellbookTabAdapter extends FragmentPagerAdapter {
    private Context mContext;
    private CharacterInfo myCharacter;

    public SpellbookTabAdapter(Context context, CharacterInfo ch, FragmentManager fm) {
        super(fm);
        mContext = context;
        myCharacter = ch;
    }

    @Override
    public Fragment getItem(int position) {
        Bundle bundle = new Bundle();
        if(position == 0) {
            PreparedSpellsFragment prepared = new PreparedSpellsFragment();
            bundle.putParcelable("character", myCharacter);
            prepared.setArguments(bundle);
            return prepared;
        } else if(position == 1) {
            MySpellbookFragment myspellbook = new MySpellbookFragment();
            bundle.putParcelable("character", myCharacter);
            myspellbook.setArguments(bundle);
            return myspellbook;
        } else if(position == 2) return new FullSpellbookFragment();
        else return null;
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        if(position == 0) return "Prepared";
        else if(position == 1) return "My Spells";
        else if(position == 2) return "All Spells";
        else return "";
    }
}

Here is the PreparedSpellsFragment class. The code is almost identical in the MySpellbookFragment class (with the exception of how the fragment interacts with the object):

package edu.uml.android.adventurersarchive;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;

import java.util.List;
import java.util.Map;

import edu.uml.android.adventurersarchive.character.CharacterInfo;
import edu.uml.android.adventurersarchive.info.Spell;

public class PreparedSpellsFragment extends Fragment {
    private SpellListAdapter adapter;
    private List<String> groupHeaders;
    private Map<String, List<Spell>> groupItems;

    public PreparedSpellsFragment() {
        Bundle bundle = getArguments();
        CharacterInfo myCharacter = (CharacterInfo) bundle.getParcelable("character");
        prepareGroups(myCharacter);
    }

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

        adapter = new SpellListAdapter(groupHeaders, groupItems);
        ExpandableListView expView = (ExpandableListView) rootView.findViewById(R.id.spell_list);
        expView.setAdapter(adapter);

        expView.setOnChildClickListener(new OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
                // TODO: Launch activity to show detailed information about the spell.
                return false;
            }
        });

        return rootView;
    }

    private void prepareGroups(CharacterInfo myCharacter) {
        // TODO: Take spells in player's prepared list and populate the groups and their items.
        if(myCharacter != null) {

        }
    }
}

I get an error saying that in the PreparedSpellsFragment constructor, I'm invoking the "getParcelable()" method on a null object reference, suggesting the Bundle object retrieved from "getArguments()" is null, but I can't see any reason for the bundle itself to be null, short of maybe an OutOfMemoryException, where it could not allocate space for the object. I could understand if maybe the object just hadn't been passed correctly or if there was a typo in the string for the key representing the object, but no... it says the Bundle object itself is null.

Can anyone figure out what the cause is?

Answer 1

Bundle bundle = getArguments();
CharacterInfo myCharacter = (CharacterInfo) bundle.getParcelable("character");
prepareGroups(myCharacter);

Write this code in onCreateView() and check.

Answer 2

You are checking the Bundle in the constructor. Get rid of the constructors and check the Bundle in onCreateView() of the fragment instead.