Fragment's on CreateView is not called when using ViewPager

Question

I'm developing an Android Application where I have a ViewPager in my MainActivity, consisting of 3 Fragments. The Problem is as follows, when I swipe to the 3rd fragment, and get back to the 1st one, onCreateView of fragment 1 is called which is what I really want, however, If I swipped to the 2nd fragment only, and returned to the 1st one, onCreateView is not called! I need to find a solution to this problem, I spent hours trying to find a solution but didn't know to solve it. Here's the code related to the ViewPager in my MainActivity

    private void setupViewPager(final ViewPager viewPager) {
    final ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFrag(new voting(), "ONE");
    adapter.addFrag(new dashboard(), "TWO");
    adapter.addFrag(new chats(), "THREE");
    myAdapter=adapter;
    viewPager.setAdapter(adapter);
    viewPager.setOffscreenPageLimit(0);
}

private class ViewPagerAdapter extends FragmentStatePagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<Fragment>();
    private final List<String> mFragmentTitleList = new ArrayList<String>();

    private ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        Log.i("getItem","getItem");
        return mFragmentList.get(position);
    }


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

    private void addFrag(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    //added newly
    @Override
    public int getItemPosition(Object object){
        return PagerAdapter.POSITION_NONE;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return null;
    }
}

"If I swipped to the 2nd fragment only, and returned to the 1st one, onCreateView is not called" -- if you mean that `onCreateView()` is not called again on the first fragment, that is perfectly normal. "I need to find a solution to this problem" -- why do you think that it is a problem? — CommonsWare, Sep 12 '17 at 14:25
@CommonsWare Yes this is what I mean, but did not find a solution yet — Ahmed Khairy, Sep 12 '17 at 14:31

score 2 · Answer 1 · edited Oct 04 '19 at 12:02

2

This is intended behavior with a FragmentPagerAdapter. If the fragment was already created and is still in memory, it is just reattached to the ViewPager. Hence, the reason why onCreateView(...) isn't called a second time.

Implementation of PagerAdapter that represents each page as a Fragment that is persistently kept in the fragment manager as long as the user can return to the page.

You're using a FragmentStatePagerAdapter which is a subclass of FragmentPagerAdapter, so it inherits this behavior.

Generally, it's not a good idea to recreate a view on every page change, as that is expensive and can lead to non smooth scrolling. If you had some logic in onCreateView(...) that you want to run again on each fragment change, then I suggest looking into ViewPager.OnPageChangeListener interface.

edited Oct 04 '19 at 12:02

Firdavs Khodzhiev

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answered Sep 12 '17 at 15:09

Jon

1,715
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what if my logic is somehow related to the inflater in onCreateView and ViewGroup and that stuff? how can i execute this logic from the mainActivity? – Ahmed Khairy Sep 12 '17 at 15:17
1

Use the inflater to create views, and hold references to those views in the fragment to interact with them later. You shouldn't need an inflater after `onCreateView(...)` unless you're dynamically creating views for some reason. Update your question with your inflater use case and maybe we can suggest a better pattern :) – Jon Sep 12 '17 at 15:23

Fragment's on CreateView is not called when using ViewPager

1 Answers1