Android-setArguments在FragmentPagerAdapter中进行片段化

Question

I've got an AppCompatActivity that has a fragment on it called TabbedScoreboardFragment ,

Inside that fragment there is a Tabbar Layout with ViewPager , and the class SectionsPagerAdapter that subclass from FragmentPagerAdapter .

That is my SectionsPagerAdapter

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    private static final String ME_FRAGMENT_TAG = "meFragment";
    private static final String FRIENDS_FRAGMENT_TAG = "friendsFragment";

    SectionsPagerAdapter(FragmentManager fm) { super(fm); }

    @Override
    public Fragment getItem(int position) {
        if (position == 0) {
            ScoreboardListFragment friendScoreboardListFragment = (ScoreboardListFragment) getChildFragmentManager().findFragmentByTag(FRIENDS_FRAGMENT_TAG);
            if (friendScoreboardListFragment == null) {
                friendScoreboardListFragment = ScoreboardListFragment.newInstance(UserType.friend);
            }
            return friendScoreboardListFragment;
        } else {
            ScoreboardListFragment meScoreboardListFragment = (ScoreboardListFragment) getChildFragmentManager().findFragmentByTag(ME_FRAGMENT_TAG);
            if (meScoreboardListFragment == null) {
                meScoreboardListFragment = ScoreboardListFragment.newInstance(UserType.me);
            }
            return meScoreboardListFragment;
        }
    }

    @Override
    public int getCount() {
        return 2;
    }
}

The problem starts here:

I'm trying to set the arguments of one of the fragments that I've passed into the getItem function, but I can't get the fragment itself, cause it isn't FragmentTransaction that has the replace function so it could take a tag and with my the tag i could identify the fragment, get it and fire the function setArguments(Bundle bundle)

What I've tried to do in TabbedScoreboardFragment is:

public class TabbedScoreboardFragment extends Fragment {

    private static final String ME_FRAGMENT_TAG = "meFragment";
    private static final String FRIENDS_FRAGMENT_TAG = "friendsFragment";

    private ViewPager viewPager;
    private SectionsPagerAdapter sectionsPagerAdapter;

    enum UserType {
         me, friend
    }

    public static TabbedScoreboardFragment newInstance() {
        return new TabbedScoreboardFragment();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_tabbed_scoreboard, container, false);
        this.viewPager = view.findViewById(R.id.container);
        this.sectionsPagerAdapter = new SectionsPagerAdapter(getChildFragmentManager());
        this.viewPager.setAdapter(this.sectionsPagerAdapter);

        TabLayout tabLayout = view.findViewById(R.id.tabs);
        this.viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(this.viewPager));
        this.viewPager.setCurrentItem(1);
        return view;
    }

    @Override
    public void setArguments(Bundle args) {
        ArrayList<MyScores.MyScore> myScores = args.getParcelableArrayList("myScores");
        if (myScores != null) {
            for (int i = 0; i < this.sectionsPagerAdapter.getCount(); i++) {
                if (this.sectionsPagerAdapter.getItem(i) instanceof ScoreboardListFragment) {
                    ScoreboardListFragment item = (ScoreboardListFragment) this.sectionsPagerAdapter.getItem(i);
                    Bundle myScoresBundle = new Bundle();
                    myScoresBundle.putParcelableArrayList("myScores", myScores);
                    item.setArguments(myScoresBundle);
                }
            }
        } else {
            super.setArguments(args);
        }
    }
}

But when I'm doing this.sectionsPagerAdapter.getItem(i) it always creating a new instance of ScoreboardListFragment instead to use and retrieve the existing one.

Thanks for helpers!

Answer 1

Not all the fragments inside are created when you are trying to pass the arguments. You will have to pass the data in another way or to "ask" for the data when you are creating/showing the fragment

Answer 2

First of all you should not create the create the fragments inside the get item type, because you are recreating the fragment every time the fragments l is on screen. What you should do is initiate the adapter with a list of fragments, so then you can have more than two fragments but also the fragments would be just initialize once so the instance is the same as when you initialized them with setArgs.