Bundle null in fragment

Question

When i try to pass bundle variables to my Fragment in android they return as null in the fragment itself, yes I know this question has been asked a lot but this is my first 5 weeks in android and i am completely new to fragments and passing bundles

this is the hero activity code (inside on create)

// create bundle of variables
    final Bundle bundle = new Bundle();
    bundle.putString("description",description);
    bundle.putString("affiliation",affiliation);
    bundle.putString("role",role);
    bundle.putString("realName",realName);
    bundle.putString("occupation",occupation);
    bundle.putString("base",base);
    bundle.putString("backstory",backstory);
    bundle.putInt("difficulty",difficulty);
    bundle.putInt("age",age);

    // pass data to fragments
    FragmentTransaction transaction = getFragmentManager().beginTransaction();


    HeroDescriptionFragment descriptionFragment = new HeroDescriptionFragment();
    descriptionFragment.setArguments(bundle);

    HeroStoryFragment storyFragment = new HeroStoryFragment();
    storyFragment.setArguments(bundle);

    transaction.commit();

here i am trying to read the bundle in the fragment:

 @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootView = inflater.inflate(R.layout.fragment_hero_description, container, false);

    // populate hero description
    description = this.getArguments().getString("description");
    TextView heroDesc = (TextView) rootView.findViewById(R.id.heroDescription);
    heroDesc.setText(description);

    return rootView;
}

all fragments are created via this pager adapter :

    public class PageAdapter extends FragmentStatePagerAdapter {

    int numberOfTabs;

    public PageAdapter(FragmentManager manager, int numberOfTabs) {
        super(manager);
        this.numberOfTabs =  numberOfTabs;
    }
    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return new HeroDescriptionFragment();
            case 1:
                return new HeroStoryFragment();
            default:
                return null;
        }
    }

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

I have the feeling i am really close to solving this but i can't figure this out on my own and my teacher has 0 experience in fragments.

OneCricketeer · Accepted Answer · 2019-12-05 05:42:27Z

1

Your problem is you are trying to manage Fragments in two different ways - manually and with a ViewPager. These are contradictory - choose one and only one.

You are setting the arguments Bundles in a transaction and then having the Adapter return Fragments that have no arguments set. To fix your problem, you will have to refactor your ViewPager method to set the arguments:

@Override
public Fragment getItem(int position) {
    switch (position) {
        case 0:
            Fragment frag = new HeroDescriptionFragment();
            frag.setArguments(createBundle());
            return frag;
        case 1:
            Fragment frag = new HeroStoryFragment();
            frag.setArguments(createBundle());
            return frag;
        default:
            return null;
    }
}

where createBundle() a method for creating the bundle as in your original code.

edited Dec 5, 2019 at 5:42

OneCricketeer

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answered Nov 8, 2017 at 8:47

David Rawson

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6 Comments

Zoe - Save the data dump Over a year ago

though it's still good practice to keep an instance of the fragments and rather pass new data to the instance than constantly creating a new one, considering memory usage

David Rawson Over a year ago

@Zoe I'm sorry but I don't think that's correct - getItem basically means createItem and the PagerAdapter handles caching itself

Zoe - Save the data dump Over a year ago

if you try creating an Activity with tabs and create an AsyncThread that launches in onCreate (to delay the start) and set text in a TExtView from it, you''ll see that it's blank every time the fragment is opened if you return a new instance. There's no caching by default with it at least

David Rawson Over a year ago

@Zoe caching Fragments yourself can be a source of memory leaks. The FragmentManager manages these for you. For instance, if you pause and resume your Activity the previous instances of the Fragment will be reused without a call to getItem(). Also, the FragmentManager will attempt to save instance state of your Fragments on onSaveInstanceState in your Activity and then attempt to restore them in onCreate()

user5486075 Over a year ago

I've put the createBundle() in the heroActivity class and call it like so: heroActivity.createBundle() where the function is declared as a bundle and all the bundle code is moved inside of it and returned once the variables are set, however i get a null reference exeption in the PageAdapter class

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himel · Accepted Answer · 2017-11-08 12:23:24Z

0

use a static method in your fragment class like this

public static MyFragment newInstance(String data1,String data2){
 MyFragment fragment=new MyFragment();
Bundle budle=new Bundle();
bundle.putString("key",data1);
....
fragment.setArguments(bundle);
return fragment;
}


//then create new Fragment like this
MyFragment f=MyFragment.newInstance("a","b");
return f;

answered Nov 8, 2017 at 12:23

himel

5106 silver badges15 bronze badges

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