Я не могу обновлять Контент в ViewPager.

Вопрос: Что такое отношения и правильного использования методов instantiateItem() и getItem() в FragmentPagerAdapter класс?

Я использовал только getItem() для создания экземпляра и вернуть мои фрагменты:

@Override
public Fragment getItem(int position) {
    return new MyFragment(context, paramters);
}

Этот работал хорошо (но как сказал я не могу изменить содержимое).

Так что я нашел это: ViewPager PagerAdapter не обновляя вид

Особенно тот, в котором он рассказал о методе instantiateItem():

"Мой подход заключается в том, чтобы использовать setTag() метод для любого инстанцировать посмотреть в instantiateItem() метод"

Так что теперь я хочу реализовать instantiateItem() чтобы это сделать. Но я не знаю, что мне придется туда вернуться (возвращение объекта) и какова связь с getItem(инт позиции)?

В настоящее время я использую getItem чтобы создать фрагмент, что не так? But then do I have to put the fragments in instance variable, or not implement getItem() at all...? I just don't understand it.

I tried reading the reference:

  • public abstract Fragment getItem (int position)

    Return the Fragment associated with a specified position.

  • public Object instantiateItem (ViewGroup container, int position)

    Create the page for the given position. The adapter is responsible for adding the view to the container given here, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup). Parameters

    container The containing View in which the page will be shown. position The page position to be instantiated.

    Returns

    Returns an Object representing the new page. This does not need to be a View, but can be some other container of the page.

... но я все равно не понимаю, как они связаны между собой и что я должен сделать.

Here's my code. I'm using support package v4.

ViewPagerTest

public class ViewPagerTest extends FragmentActivity {
    private ViewPager pager;
    private MyFragmentAdapter adapter; 

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.pager1);

        pager = (ViewPager)findViewById(R.id.slider);

        String[] data = {"page1", "page2", "page3", "page4", "page5", "page6"};

        adapter = new MyFragmentAdapter(getSupportFragmentManager(), 6, this, data);
        pager.setAdapter(adapter);

        ((Button)findViewById(R.id.button)).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                reload();
            }
        });
    }

    private void reload() {
        String[] data = {"changed1", "changed2", "changed3", "changed4", "changed5", "changed6"};
        //adapter = new MyFragmentAdapter(getSupportFragmentManager(), 6, this, data);
        adapter.setData(data);
        adapter.notifyDataSetChanged();
        pager.invalidate();

        //pager.setCurrentItem(0);
    }
}

MyFragmentAdapter

class MyFragmentAdapter extends FragmentPagerAdapter {
    private int slideCount;
    private Context context;
    private String[] data;

    public MyFragmentAdapter(FragmentManager fm, int slideCount, Context context, String[] data) {
        super(fm);
        this.slideCount = slideCount;
        this.context = context;
        this.data = data;
    }

    @Override
    public Fragment getItem(int position) {
        return new MyFragment(data[position], context);
    }

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

    public void setData(String[] data) {
        this.data = data;
    }

    @Override
    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }
}

MyFragment

public final class MyFragment extends Fragment {
    private String text;

    public MyFragment(String text, Context context) {
        this.text = text;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.slide, null);
        ((TextView)view.findViewById(R.id.text)).setText(text);

        return view;
    }
}

Here is also somebody with a similar problem, no answers...

http://www.mail-archive.com/android-developers@googlegroups.com/msg200477.html

share|improve this question
    
To get a better understanding of the components involved it might help to read my tutorial about a tabbed ViewPager with separate back navigation history. It comes with a working example on GitHub and additional resources: medium.com/@nilan/… – marktani Jan 3 '16 at 17:45
    
got some issue stackoverflow.com/questions/40149039/… – albert Oct 21 '16 at 12:25

18 Answers 18

up vote 516 down vote accepted

When using FragmentPagerAdapter or FragmentStatePagerAdapter, it is best to deal solely with getItem() and not touch instantiateItem() at all. The instantiateItem()-destroyItem()-isViewFromObject() interface on PagerAdapter is a lower-level interface that FragmentPagerAdapter uses to implement the much simpler getItem() interface.

Before getting into this, I should clarify that

если вы хотите перейти из фактического фрагменты, которые выводятся на экран, вы должны избегать FragmentPagerAdapter и использовать FragmentStatePagerAdapter.

Более ранняя версия этого ответа сделал ошибку, используя FragmentPagerAdapter на своем примере - это не сработает, потому что FragmentPagerAdapter никогда не разрушает фрагмент после того, как оно отображается в первый раз.

I don't recommend the setTag() and findViewWithTag() workaround provided in the post you linked. As you've discovered, using setTag() and findViewWithTag() doesn't work with fragments, so it's not a good match.

The right solution is to override getItemPosition(). When notifyDataSetChanged() is called, ViewPager calls getItemPosition() on all the items in its adapter to see whether they need to be moved to a different position or removed.

By default, getItemPosition() returns POSITION_UNCHANGED, which means, "This object is fine where it is, don't destroy or remove it." Returning POSITION_NONE fixes the problem by instead saying, "This object is no longer an item I'm displaying, remove it." Так что это имеет эффект удаления и повторного создания каждого отдельного элемента в вашем адаптере.

Это совершенно законные исправить! Это исправление позволяет notifyDataSetChanged вести себя как обычный адаптер без зрения утилизации. Если вы реализуете это исправить и производительность удовлетворительная, ты вне конкуренции. Job done.

If you need better performance, you can use a fancier getItemPosition() implementation. Вот пример для пейджера создания фрагментов из списка строк:

ViewPager pager = /* get my ViewPager */;
// assume this actually has stuff in it
final ArrayList titles = new ArrayList();

FragmentManager fm = getSupportFragmentManager();
pager.setAdapter(new FragmentStatePagerAdapter(fm) {
    public int getCount() {
        return titles.size();
    }

    public Fragment getItem(int position) {
        MyFragment fragment = new MyFragment();
        fragment.setTitle(titles.get(position));
        return fragment;
    }

    public int getItemPosition(Object item) {
        MyFragment fragment = (MyFragment)item;
        String title = fragment.getTitle();
        int position = titles.indexOf(title);

        if (position >= 0) {
            return position;
        } else {
            return POSITION_NONE;
        }
    }
});

С этой реализацией, только фрагменты показа новых названий будет отображаться. Любые фрагменты показа титров, которые все еще находятся в списке, будут перемещены в новую позицию в списке, и фрагменты с названиями, которые больше не в списке вообще будет уничтожено.

Что, если фрагмент не был воссоздан, но должен быть обновлен в любом случае? Обновления для гостиной фрагмента лучше всего заниматься самому фрагменту. Вот и будете получать фрагмент, в конце концов - это его собственный контроллер. A fragment can add a listener or an observer to another object in onCreate(), and then remove it in onDestroy(), thus managing the updates itself. You don't have to put all the update code inside getItem() like you do in an adapter for a ListView or other AdapterView types.

Одна последняя вещь - просто потому что FragmentPagerAdapter не уничтожить фрагмент не значит, что getItemPosition совершенно бесполезна в FragmentPagerAdapter. Вы все еще можете использовать этот обратный вызов, чтобы изменить порядок отображения фрагментов в ViewPager. Он никогда не удалить их полностью из FragmentManager, хотя.

share|improve this answer
4  
Doesn't work, it's still not updating anything... posted my code. – Ixx Jun 2 '12 at 18:53
50  
Okay, figured out the problem - you need to use FragmentStatePagerAdapter rather than FragmentPagerAdapter. FragmentPagerAdapter never removes fragments from the FragmentManager, it only detaches and attaches them. Check the docs for more info - in general, you only want to use FragmentPagerAdapter for fragments that are permanent. I've edited my example with the correction. – Bill Phillips Jun 4 '12 at 17:38
1  
I will review this at some point later... thanks for your answer. And then I accept your answer if it works. Before your last comment I implemented to remove and add a new ViewPager each time and that works. Not very good solution, but I don't have time now to change it. – Ixx Jun 12 '12 at 12:08
9  
You're right, changing the class of the adapter to FragmentStatePagerAdapter fixed all my trouble. Thanks! – Ixx Jun 17 '12 at 22:06
1  
I think you'll get better feedback if you submit a standalone question for that, darkravedev. – Bill Phillips Aug 14 '13 at 15:34

Вместо возврата POSITION_NONE от getItemPosition() и вызывая полный вид отдыха, сделать это:

//call this method to update fragments in ViewPager dynamically
public void update(UpdateData xyzData) {
    this.updateData = xyzData;
    notifyDataSetChanged();
}

@Override
public int getItemPosition(Object object) {
    if (object instanceof UpdateableFragment) {
        ((UpdateableFragment) object).update(updateData);
    }
    //don't return POSITION_NONE, avoid fragment recreation. 
    return super.getItemPosition(object);
}

Ваш фрагментов следует осуществлять UpdateableFragment интерфейс:

public class SomeFragment extends Fragment implements
    UpdateableFragment{

    @Override
    public void update(UpdateData xyzData) {
         // this method will be called for every fragment in viewpager
         // so check if update is for this fragment
         if(forMe(xyzData)) {
           // do whatever you want to update your UI
         }
    }
}

and the interface:

public interface UpdateableFragment {
   public void update(UpdateData xyzData);
}

Your data class:

public class UpdateData {
    //whatever you want here
}
share|improve this answer
1  
Означает ли это, что ваш файл mainactivity также должен реализовывать интерфейс ??? Please help me out here. In my current implementation, I am using my MainActivity class as a communicator between the fragments, so I was confused about this solution. – Rakeeb Rajbhandari Nov 20 '13 at 9:44
1  
Ok I have answered at another place with full implementation where I am updating Fragment dynamically, have a look: stackoverflow.com/questions/19891828/… – M-WaJeEh Nov 20 '13 at 12:50
    
@M-WaJeEh maybe some example please!!! i have a listview with list of cities and after selecting city opens viewpager (3 pages) with information about this city. it works ok. but after selecting another city viewpager shows only the 3d page on refreshes the 1-st page only after swiping pages? thw 2d page is always blank. thanks – SERG Apr 22 '14 at 12:45
3  
among all the stuff i ve seen for the past 2.5 days of my work life.. this is the only one that worked for me.. all sorts of arigato, thanks, spaciba, sukran .. n. – Zortkun Mar 5 '15 at 17:05
2  
Mother of Dragons!, this works like a charm, the only solution worked for me... thx a lot !! – Sebastián Guerrero Apr 17 '15 at 20:09

I have encountered this problem and finally solved it today, so I write down what I have learned and I hope it is helpful for someone who is new to Android's ViewPager and update as I do. I'm using FragmentStatePagerAdapter in API level 17 and currently have just 2 fragments. I think there must be something not correct, please correct me, thanks. enter image description here

  1. Сериализованные данные должны быть загружены в память. This can be done using a CursorLoader/AsyncTask/Thread. Будет ли это автоматически загружаются зависит от вашего кода. Если вы используете CursorLoaderэто автоматически загружаться так как есть зарегистрированные данные наблюдателя.

  2. After you call viewpager.setAdapter(pageradapter), the adapter's getCount() is constantly called to build fragments. So if data is being loaded, getCount() can return 0, thus you don't need to create dummy fragments for no data shown.

  3. After the data is loaded, the adapter will not build fragments automatically since getCount() is still 0, so we can set the actually loaded data number to be returned by getCount(), then call the adapter's notifyDataSetChanged(). ViewPager begin to create fragments (just the first 2 fragments) by data in memory. It's done before notifyDataSetChanged() is returned. Then the ViewPager has the right fragments you need.

  4. If the data in the database and memory are both updated (write through), or just data in memory is updated (write back), or only data in the database is updated. In the last two cases if data is not automatically loaded from the database to memory (as mentioned above). The ViewPager and pager adapter just deal with data in memory.

  5. So when data in memory is updated, we just need to call the adapter's notifyDataSetChanged(). Since the fragment is already created, the adapter's onItemPosition() will be called before notifyDataSetChanged() returns. Nothing needs to be done in getItemPosition(). Then the data is updated.

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4  
Do you have a code example of this? – Edmund Rojas Aug 27 '13 at 14:30
    
i have found the nothing need to do after you update data(in memeory), just call notifyDataSetChanged() then just updated automatically, because the fragment(with chartview) i use will refresh itself. if it's not, like a static fragment, i will have to call onItemPositon() and returns POSITION_NONE sorry about that – oscarthecat Sep 1 '13 at 7:54
    
where to notifyDataSetChanged()... – GvSharma Jun 16 '14 at 8:56
    
Does anyone have an idea of what tool was used to make that diagram? – JuiCe Aug 11 '16 at 15:17

Try destroyDrawingCache() on ViewPager after notifyDataSetChanged() in your code.

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3  
definitely the only solution that worked – Rafael Ruiz Dec 12 '14 at 22:34
2  
Same here. Works great thank you. I had especially a tough time cause I am not using Fragments in my view pager. So thank you! – Seth Apr 8 '15 at 20:12

for those who still face the same problem which i faced before when i have viewpager with seven fragments. the default for these fragments to load the english content from service but the problem here that i want to change the language from settins activity and after finish Settings activity i want viewpager in main activity to refresh the fragments to match the langauge selection from the user and load the arabic content if user choose arabic here what i did to work from the first time

1-you must use vFragmentStatePagerAdapter as mentioned above.

2-on mainActivity i overrided the onResume and did the following

if (!(mPagerAdapter == null)) {

            mPagerAdapter.notifyDataSetChanged();


        }

3-i ovveride the getItemPosition() in mPagerAdapter and make it return POSITION_NONE.

@Override
        public int getItemPosition(Object object) {

            return POSITION_NONE;
        }

works like charm

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This is the only thing that works for me right now! Thanks. – cherry-wave Jun 16 '16 at 18:56
    
Works except in one situtaion. When you delete last item in viewPager. Then it doesn't remove from list. – Vlado Pandžić Jul 11 '16 at 13:57
    
This is the simplest and only working solution for me too. Thanks. – Zafer Jun 10 at 17:21

After hours of frustration while trying all the above solutions to overcome this problem and also trying many solutions on other similar questions like this, this and this which all FAILED with me to solve this problem and to make the ViewPager to destroy the old Fragment and fill the pager with the new Fragments. I have solved the problem as following:

1) Make the ViewPager class to extends FragmentPagerAdapter as following:

 public class myPagerAdapter extends FragmentPagerAdapter {

2) Create an Item for the ViewPager that store the title and the fragment as following:

public class PagerItem {
private String mTitle;
private Fragment mFragment;


public PagerItem(String mTitle, Fragment mFragment) {
    this.mTitle = mTitle;
    this.mFragment = mFragment;
}
public String getTitle() {
    return mTitle;
}
public Fragment getFragment() {
    return mFragment;
}
public void setTitle(String mTitle) {
    this.mTitle = mTitle;
}

public void setFragment(Fragment mFragment) {
    this.mFragment = mFragment;
}

}

3) Make the constructor of the ViewPager take my FragmentManager instance to store it in my class as following:

private FragmentManager mFragmentManager;
private ArrayList mPagerItems;

public MyPagerAdapter(FragmentManager fragmentManager, ArrayList pagerItems) {
    super(fragmentManager);
    mFragmentManager = fragmentManager;
    mPagerItems = pagerItems;
}

4) Create a method to re-set the adapter data with the new data by deleting all the previous fragment from the fragmentManager itself directly to make the adapter to set the new fragment from the new list again as following:

public void setPagerItems(ArrayList pagerItems) {
    if (mPagerItems != null)
        for (int i = 0; i < mPagerItems.size(); i++) {
            mFragmentManager.beginTransaction().remove(mPagerItems.get(i).getFragment()).commit();
        }
    mPagerItems = pagerItems;
}

5) From the container Activity or Fragment do not re-initialize the adapter with the new data. Set the new data through the method setPagerItems with the new data as following:

ArrayList pagerItems = new ArrayList();
    pagerItems.add(new PagerItem("Fragment1", new MyFragment1()));
    pagerItems.add(new PagerItem("Fragment2", new MyFragment2()));

    mPagerAdapter.setPagerItems(pagerItems);
    mPagerAdapter.notifyDataSetChanged();

I hope it helps.

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can you help me in my issue stackoverflow.com/questions/40149039/… – albert Oct 22 '16 at 5:36
    
can you please help me with this issue stackoverflow.com/questions/41547995/… – viper Jan 17 at 4:31

For some reason none of the answers worked for me so I had to override the restoreState method without calling super in my fragmentStatePagerAdapter. Code:

private class MyAdapter extends FragmentStatePagerAdapter {

    // [Rest of implementation]

    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {}

}
share|improve this answer
    
After trying everything else in this SO answer, this is the one that worked for me. I'm finish()ing an activity that's returning to the Activity that hosts the PagerAdapter in question. I want all my fragments to be re-created in this case because the Activity that I just finished may have changed the state that is used to draw the fragments. – JohnnyLambada Nov 23 '16 at 1:28
    
This worked for me too : thank you !!! – Jonatha ANTOINE Feb 21 at 20:59
    
OMG.. it works.. it works.. kudos :D In my case i need to remove viewpager current item object. but the current fragment is not updating after trying all the above methods/steps. – Rahul Khurana May 5 at 7:53

I slightly modified the solution provided by Bill Phillips to suit my needs

private class PagerAdapter extends FragmentStatePagerAdapter{
    Bundle oBundle;
    FragmentManager oFragmentManager;
    ArrayList oPooledFragments;

public PagerAdapter(FragmentManager fm) {
    super(fm);
    oFragmentManager=fm;

    }
@Override
public int getItemPosition(Object object) {

    Fragment oFragment=(Fragment)object;
    oPooledFragments=new ArrayList<>(oFragmentManager.getFragments());
    if(oPooledFragments.contains(oFragment))
        return POSITION_NONE;
    else
        return POSITION_UNCHANGED;
    } 
}

so that the getItemPosition() returns POSITION_NONE only for those fragments which are currently in the FragmentManager when getItemPosition is called. (Note that this FragmentStatePager and the ViewPager associated with it are contained in a Fragment not in a Activity)

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I had a similar problem but don't want to trust on the existing solutions (hard coded tag names etc.) and I couldn't make M-WaJeEh's solution work for me. Here is my solution:

I keep references to the fragments created in getItem in an array. This works fine as long as the activity is not destroyed due to configurationChange or lack of memory or whatever (--> when coming back to the activity, fragments return to their last state without 'getItem' being called again and thus without updating the array).

To avoid this problem I implemented instantiateItem(ViewGroup, int) and update my array there, like this:

        @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Object o = super.instantiateItem(container, position);
        if(o instanceof FragmentX){
            myFragments[0] = (FragmentX)o;
        }else if(o instanceof FragmentY){
            myFragments[1] = (FragmentY)o;
        }else if(o instanceof FragmentZ){
            myFragments[2] = (FragmentZ)o;
        }
        return o;
    }

So, on the one hand I'm happy that I found a solution that works for me and wanted to share it with you, but I also wanted to ask whether somebody else tried something similar and whether there is any reason why I shouldn't do it like that? So far it works very good for me...

share|improve this answer
    
I've done something related in stackoverflow.com/a/23427215/954643, although you should probably remove the item from myFragments in public void destroyItem(ViewGroup container, int position, Object object) as well so you don't grab a stale fragement reference. – qix May 8 '14 at 18:28

If you want to use FragmentStatePagerAdapter, please take a look at https://code.google.com/p/android/issues/detail?can=2&start=0&num=100&q=&colspec=ID%20Type%20Status%20Owner%20Summary%20Stars&groupby=&sort=&id=37990. There are issues with FragmentStatePagerAdapter that may or may not trouble your use case.

Also, link has few solutions too..few may suit to your requirement.

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From that URL I found solution. I used the modified FragmentStatePagerAdapter from this gist gist.github.com/ypresto/8c13cb88a0973d071a64 in my code and it started to work as supposed to be. – Rafael Muhamedzyanov Feb 22 '16 at 4:02
    
Cool. Yes. Link has few solutions too. – cgr Feb 22 '16 at 7:53

I use EventBus library to update Fragment content in ViewPager. The logic is simple, just like document of EventBus how to do. It is no need to control FragmentPagerAdapter instance. The code is here:

1: Define events

Define which message which is needed to update.

public class UpdateCountEvent {
    public final int count;

    public UpdateCountEvent(int count) {
        this.count = count;
    }
}

2.Prepare subscribers

Write below code in the Fragment which is needed update.

@Override
public void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
public void onStop() {
    EventBus.getDefault().unregister(this);  
    super.onStop();
}

public void onEvent(UpdateCountEvent event) {//get update message
    Toast.makeText(getActivity(), event.count, Toast.LENGTH_SHORT).show();
}

3.Post events

Write below code in other Activity or other Fragment which needs to update parameter

//input update message
EventBus.getDefault().post(new UpdateCountEvent(count));
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I had been trying so many different approaches, none really sove my problem. Below are how I solve it with a mix of solutions provided by you all. Thanks everyone.

class PagerAdapter extends FragmentPagerAdapter {

    public boolean flag_refresh=false;

    public PagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int page) {
        FragmentsMain f;
        f=new FragmentsMain();
        f.page=page;
        return f;
    }

    @Override
    public int getCount() {
        return 4;
    }

    @Override
    public int getItemPosition(Object item) {
        int page= ((FragmentsMain)item).page;

        if (page == 0 && flag_refresh) {
            flag_refresh=false;
            return POSITION_NONE;
        } else {
            return super.getItemPosition(item);
        }
    }

    @Override
    public void destroyItem(View container, int position, Object object) {

        ((ViewPager) container).removeView((View) object);
    }
}

I only want to refresh page 0 after onResume().

 adapter=new PagerAdapter(getSupportFragmentManager());
 pager.setAdapter(adapter);

@Override
protected void onResume() {
    super.onResume();

    if (adapter!=null) {
        adapter.flag_refresh=true;
        adapter.notifyDataSetChanged();
    }
}

In my FragmentsMain, there is public integer "page", which can tell me whether it is the page I want to refresh.

public class FragmentsMain extends Fragment {

private Cursor cursor;
private static Context context;
public int page=-1;
share|improve this answer

I know am late for the Party. I've fixed the problem by calling TabLayout#setupWithViewPager(myViewPager); just after FragmentPagerAdapter#notifyDataSetChanged();

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This solution won't work for everyone, but in my case, every Fragment in my ViewPager is a different class, and only one of them ever exist at a time.

With this constraint, this solution is safe and should be safe to use in production.

private void updateFragment(Item item) {

    List fragments = getSupportFragmentManager().getFragments();
    for (Fragment fragment : fragments) {

        if (fragment instanceof MyItemFragment && fragment.isVisible()) {
            ((MyItemFragment) fragment).update(item);
        }

    }
}

If you have multiple versions of the same fragment, you can use this same strategy to call methods on those fragments to determine if it is the fragment you wish to update.

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This might be of help to someone - in my case when inserting a new page the view pager was asking for the position of an existing fragment twice, but not asking for the position of the new item, causing incorrect behaviour and data not displaying.

  1. Copy the source for for FragmentStatePagerAdapter (seems to have not been updated in ages).

  2. Override notifyDataSetChanged()

    @Override
    public void notifyDataSetChanged() {
        mFragments.clear();
        super.notifyDataSetChanged();
    }
    
  3. Add a sanity check to destroyItem() to prevent crashes:

    if (position < mFragments.size()) {
        mFragments.set(position, null);
    }
    
share|improve this answer

Accepted answer is not understand, That's why added easy solution. find Working solution.

Just notify to your adapter, it's working amazing,

Reference code

 void setAdapter(int position) {
        PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager());
        viewPager.setAdapter(pagerAdapter);
        // when notify then set manually current position.
        viewPager.setCurrentItem(position);
        pagerAdapter.notifyDataSetChanged();
    }

call this code when you set adapter and when you want to refresh UI.

In Your fragment add this code for refresh Use instanceof for cast context.

((YourActivityName) getContext()).setAdapter(selectedTabPosition);

This code share only helping purpose who find working solution, Hope its helpful !

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I've gone through all the answers above and a number of others posts but still couldn't find something that worked for me (with different fragment types along with dynamically adding and removing tabs). FWIW following approach is what worked for me (in case anyone else has same issues).

public class MyFragmentStatePageAdapter extends FragmentStatePagerAdapter {
    private static final String TAB1_TITLE = "Tab 1";
    private static final String TAB2_TITLE = "Tab 2";
    private static final String TAB3_TITLE = "Tab 3";

    private ArrayList titles = new ArrayList<>();
    private Map fragmentPositions = new HashMap<>();


    public MyFragmentStatePageAdapter(FragmentManager fm) {
        super(fm);
    }


    public void update(boolean showTab1, boolean showTab2, boolean showTab3) {
        titles.clear();

        if (showTab1) {
            titles.add(TAB1_TITLE);
        }
        if (showTab2) {
            titles.add(TAB2_TITLE);
        }
        if (showTab3) {
            titles.add(TAB3_TITLE);
        }
        notifyDataSetChanged();
    }


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

    @Override
    public Fragment getItem(int position) {
        Fragment fragment = null;

        String tabName = titles.get(position);
        if (tabName.equals(TAB1_TITLE)) { 
            fragment =  Tab1Fragment.newInstance();
        } else if (tabName.equals(TAB2_TITLE)) {
            fragment =  Tab2Fragment.newInstance();
        } else if (tabName.equals(TAB3_TITLE)) {
            fragment =  Tab3Fragmen.newInstance();
        } 

        ((BaseFragment)fragment).setTitle(tabName);
        fragmentPositions.put(fragment, position);
        return fragment;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return titles.get(position);
    }

    @Override
    public int getItemPosition(Object item) {
        BaseFragment fragment = (BaseFragment)item;
        String title = fragment.getTitle();
        int position = titles.indexOf(title);

        Integer fragmentPosition = fragmentPositions.get(item);
        if (fragmentPosition != null && position == fragmentPosition) {
            return POSITION_UNCHANGED;
        } else {
            return POSITION_NONE;
        }
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        super.destroyItem(container, position, object);
        fragmentPositions.remove(object);
    }
}
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I have lived same problem and I have searched too much times. Any answer given in stackoverflow or via google was not solution for my problem. My problem was easy. I have a list, I show this list with viewpager. When I add a new element to head of the list and I refresh the viewpager nothings changed. My final solution was very easy anybody can use. When a new element added to list and want to refresh the list. Firstly set viewpager adapter to null then recreate the adapter and set i to it to viewpager.

myVPager.setAdapter(null);
myFragmentAdapter = new MyFragmentAdapter(getSupportFragmentManager(),newList);
myVPager.setAdapter(myFragmentAdapter);

Be sure your adapter must extend FragmentStatePagerAdapter

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