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View pager fragments and Tabs are out of sync android

In my project I have a tab layout and a fragments viewpager. When I load the fragments and tabs the tab index and the displayed fragment is out of sync, and also when I swipe back and forth the fragments are not in sync with the tabs. I checked the getItem(int position) and the getTitle(int position) methods both have the same position number and the corresponding entries in the ArrayList<Fragments> and the ArrayList<String> (for tab headings) are correct but some how the tabs display is out of sync with the view pager.
Here is my fragmentPagerAdapter.java
public class DetailsFragmentPagerAdapter extends FragmentPagerAdapter {
private ArrayList<Fragment> fragments;
private ArrayList<String> titles;
public DetailsFragmentPagerAdapter(FragmentManager fm) {
super(fm);
fragments = new ArrayList<>();
titles = new ArrayList<>();
}
#Override
public Fragment getItem(int position) {
return fragments.get(position);
}
#Override
public int getCount() {
return titles.size();
}
#Override
public CharSequence getPageTitle(int position) {
return titles.get(position);
}
public void setFragment(Fragment fragment, String title) {
fragments.add(fragment);
titles.add(title);
notifyDataSetChanged();
}
}
this is activity on create.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
tabLayout = (TabLayout) findViewById(R.id.detailsTabs);
viewPager = (ViewPager) findViewById(R.id.viewPager);
new GetCategoriesAsync2().execute();
}
the async task's doInBackground is calling is preparing arraylist
and the onPostExecute
#Override
protected void onPostExecute(Void aVoid) {
int size = lists.size();
ArrayList<Fragment> fragments = new ArrayList<>(size);
ArrayList<String> titles = new ArrayList<>(size);
for (int i = 0; i < lists.size(); i++) {
ArrayList<String> x = lists.get(i);
titles.add(x.remove(0));
fragments.add(DetailsListFragment.newInstance(x));
}
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentPagerAdapter = new DetailsFragmentPagerAdapter(fragmentManager);
fragmentPagerAdapter.setFragments(fragments,titles);
viewPager.setAdapter(fragmentPagerAdapter);
tabLayout.setupWithViewPager(viewPager);
progressDialog.dismiss();
}
I am using design support library 23.0.1 and the build target is 23.
how can I fix this tab layout out of sync?

if you use a TabLayout, you need to connect it to the adapter
If you're using a ViewPager together with this layout, you can use
setTabsFromPagerAdapter(PagerAdapter) which will populate the tabs
using the given PagerAdapter's page titles. You should also use a
TabLayout.TabLayoutOnPageChangeListener to forward the scroll and
selection changes to this layout like so:
ViewPager viewPager = ...;
TabLayout tabLayout = ...;
viewPager.addOnPageChangeListener(new TabLayoutOnPageChangeListener(tabLayout));

Try this, it worked for me
public class DetailsFragmentPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> fragments= new ArrayList<Fragment>();
private final List<String> titles= new ArrayList<String>();
public DetailsFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return fragments.get(position);
}
#Override
public int getCount() {
return fragments.size();
}
#Override
public CharSequence getPageTitle(int position) {
return titles.get(position);
}
public void setFragment(Fragment fragment, String title) {
fragments.add(fragment);
titles.add(title);
}
}
And Change
fragmentPagerAdapter.setFragments(fragments,titles); To
for (int i=0;i<fragments.size();i++)
{
adapter.setFragments(fragments.get(i),titles.get(i));
}

Check this out
it's a demo app that uses a TabLayout with a ViewPager
https://github.com/chrisbanes/cheesesquare
and if you don't know the number of the fragments that you will have in the ViewPager
your pageadapter should extends FragmentStatePagerAdapter
https://developer.android.com/reference/android/support/v4/app/FragmentStatePagerAdapter.html

Dynamically assign the final NUM_PAGES of viewpager

I got the screenslider to work from the android Screenslider,
put a webview in and got it to load the urls i assign to it.
It works fine but now i'd like to control the private static final int NUM_PAGES = 5;
and dynamically change it from a sqlite database numrowcount when i move to this activity.
I tried wrappers and then some but it will crash everytime.
My knowledge of java is somewhat limited elas.
Now i know this works in the oncreate
Bundle bundle = new Bundle();
bundle.putString("urlData", urlData);
ScreenSlidePageFragment fragobj = new ScreenSlidePageFragment();
fragobj.setArguments(bundle);
So i assign the url thats being used to get content within the fragment.
Now how do i control the private static final int NUM_PAGES = 5,
and reassign it to whatever number i want or get from the database?
I just cant get why this is such a difficult thing to create
or find on the web.
Seems to me it should be a non final static number.
I know i am totaly not getting it, but someone does ;)
Anybody any idea?
this is the code:
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
...
public class ScreenSlidePagerActivity extends FragmentActivity {
/**
* The number of pages (wizard steps) to show in this demo.
*/
private static final int NUM_PAGES = 5;
private ViewPager mPager;
private PagerAdapter mPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_screen_slide);
// Instantiate a ViewPager and a PagerAdapter.
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
}
#Override
public void onBackPressed() {
if (mPager.getCurrentItem() == 0) {
// If the user is currently looking at the first step, allow the system to handle the
// Back button. This calls finish() on this activity and pops the back stack.
super.onBackPressed();
} else {
// Otherwise, select the previous step.
mPager.setCurrentItem(mPager.getCurrentItem() - 1);
}
}
/**
* A simple pager adapter that represents 5 ScreenSlidePageFragment objects, in
* sequence.
*/
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public ScreenSlidePagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return new ScreenSlidePageFragment();
}
#Override
public int getCount() {
return NUM_PAGES;
}
}
}

Mm i turn out to be easy just make it non final and slip in a variable (int count) with the constructor.
public class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public int NUM_COUNT;
#Override
public int getCount() {
return NUM_COUNT;
}
public ScreenSlidePagerAdapter(FragmentManager fm,int count) {
super(fm);
this.NUM_COUNT = count;
}
#Override
public Fragment getItem(int position) {
return ScreenSlidePageFragment.create(position);
}
}

Fragments in viewpager

I have viewpager with some fragments and i set to each fragment my model class according which UI of fragment should be edited. That model class i set to fragment at constructor before i add that fragment to FragmentStatePagerAdapter. My problem is that after rotating screen or when system kills my application and i restore it, my fragment are recreated by system and my model class instance is lost. Even if I set new FragmentStatePagerAdapter, fragments created by system are visible. Is there any right way of achive that i create new instances of my fragments and place them into viewpager? I tried so many thinks like removing fragments from FragmentManager, adding Adapter to viewpager again, change FragmentStatePagerAdapter only to FragmentPagerAdapter and nothing helped.
My activity class with loading model classes in loader from some resource:
List<Fragment> visibleFragment = new ArrayList<Fragment>();
for (Screen screen : wizard.screens) {
if (screen.visible) {
visibleFragment.add(new ScreenUI(screen));
}
}
viewPager.setAdapter(null);
viewPager.setAdapter(new WizardPagerAdapter(getSupportFragmentManager(), visibleFragment));
My FragmentStatePagerAdapter
public class WizardPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragments;
private final int count;
public WizardPagerAdapter(FragmentManager fm, List<Fragment> fragments) {
super(fm);
mFragments = fragments;
count = mFragments.size();
}
#Override
public Fragment getItem(int index) {
return mFragments.get(index);
}
#Override
public int getCount() {
return count;
}
}

try add in Manifest android:configChanges="orientation|keyboardHidden|screenSize" to activity.
OR something like that
public class ViewPagerTaskAdapter extends FragmentStatePagerAdapter {
Map<Integer, FragmentViewTask> fragmentsTask = new HashMap<Integer, FragmentViewTask>();
#Override
public Fragment getItem(int arg0) {
FragmentViewTask myFragment = FragmentViewTask.newInstance(arg0,
tasks.get(arg0));
fragmentsTask.put(arg0, myFragment);
return myFragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
fragmentsTask.remove(position);
}
public FragmentViewTask getFragment(int key) {
return fragmentsTask.get(key);
}
#Override
public int getCount() {
if (tasks != null)
return tasks.size();
return 0;
}
}

Have you tried using onRetainInstance(true) on your Fragments?
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}

Android FragmentStatePagerAdapter

I'm working with a FragmentStatePagerAdapter using this example.
The MyAdapter class is implemented as follows:
public static class MyAdapter extends FragmentStatePagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
#Override
public int getCount() {
return NUM_ITEMS;
}
#Override
public Fragment getItem(int position) {
return ArrayListFragment.newInstance(position);
}
}
The ListFragment class includes the following method to create a new instance:
/**
* Create a new instance of CountingFragment, providing "num"
* as an argument.
*/
static ArrayListFragment newInstance(int num) {
ArrayListFragment f = new ArrayListFragment();
// Supply num input as an argument.
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
When I create a new fragment state pager adapter in my activity, getItem is called, which in turn calls the newInstance method in the ListFragment class. This is great when I want to create a new fragment.
But it's not clear to me how to modify getItem (if even needed) to get the fragment object when it already exists and the user pages from, for example, page 2 to page 1. I'd like my Activity to retrieve that existing, previously created fragment so that it can run an inner class AsyncMethod, which resides in the fragment class.

I think the solution is much simpler than the answers provided.
If you take a look at the source of FragmentStatePagerAdapter.instantiateItem(), you'll notice that instantiateItem() handles this logic for you, and thus your implementation of getItem() should always return a new instance.
So in order to return an existing Fragment, simply do (assuming you're calling from ViewPager):
Fragment f = (Fragment) getAdapter().instantiateItem(this, getCurrentItem());

While #imiric's solution is very concise, it still bothers me that it requires knowledge of the implementation of the class. My solution involves adding the following to your adapter, which should behave nicely with a FragmentStatePagerAdapter possibly destroying fragments:
private SparseArray<WeakReference<Fragment>> mFragments = new SparseArray<>();
#Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment f = (Fragment) super.instantiateItem(container, position);
mFragments.put(position, new WeakReference<>(f)); // Remember what fragment was in position
return f;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
mFragments.remove(position);
}
public Fragment getFragment(int position) {
WeakReference<Fragment> ref = mFragments.get(position);
Fragment f = ref != null ? ref.get() : null;
if (f == null) {
Log.d(TAG, "fragment for " + position + " is null!");
}
return f;
}

I have implemented something similar to what you have. I extended the FragmentPagerAdapter class like so:
public class ContactsFragmentPagerAdapter extends FragmentPagerAdapter {
ActionBar mActionBar;
private List<Fragment> mFragments;
public ContactsFragmentPagerAdapter(FragmentManager fm, List<Fragment> fragments) {
super(fm);
mFragments = fragments;
}
#Override
public int getCount() {
return mFragments.size();
}
#Override
public Fragment getItem(int position) {
return mFragments.get(position);
}
public void setActionBar(ActionBar bar) {
mActionBar = bar;
}
}
Notice I have added an argument to the constructor to pass in the List of Fragment objects. This way the getItem() method of this class can return any class that extends Fragment or any of its subclasses and not just one specific class ArrayListFragment like you have done.
In the Activity where I instantiate my subclass of FragmentPagerAdapter I have passed in the list of Fragment objects:
Class the instantiates the FragmentPagerAdapter
public final class ContactManager extends Activity {
private ContactsFragmentPagerAdapter mAdapter;
private ViewPager mPager;
public ActionBar mActionBar;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.contact_manager);
List<Fragment> fragments = new Vector<Fragment>();
fragments.add(Fragment.instantiate(this, ContactsListFragment.class.getName()));
fragments.add(Fragment.instantiate(this, GroupsListFragment.class.getName()));
mAdapter = new ContactsFragmentPagerAdapter(this.getFragmentManager(), fragments);
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
mPager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageScrollStateChanged(int arg0) {}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {}
#Override
public void onPageSelected(int arg0) {
mActionBar.getTabAt(arg0).select();
}
});
}
}
By accessing the variable "fragments", you can access a previously created Fragment so that you can run methods of that Fragment.

public class MyPagerAdapter extends FragmentStatePagerAdapter {
final Context m_context;
final WeakReference<Fragment>[] m_fragments;
public DetailPagerAdapter(FragmentManager fm) {
super(fm);
m_context = ...
m_fragments = new WeakReference[enter size here];
}
#Override
public Fragment getItem(int position) {
final Fragment fragment = instantiate your fragment;
m_fragments[position] = new WeakReference<Fragment>(fragment);
return fragment;
}
#Override
public int getCount() {
return ...
}
public Fragment getFragment(final int position) {
return m_fragments[position] == null ? null :
m_fragments[position].get();
}
}

Do not need modify the FragmentPagerAdapter, because fragments are cached by the FragmentManager. So you must need find inside it. Use this function to find the fragment by pager adapter position.
public Fragment findFragmentByPosition(int position) {
FragmentPagerAdapter fragmentPagerAdapter = getFragmentPagerAdapter();
return getSupportFragmentManager().findFragmentByTag(
"android:switcher:" + getViewPager().getId() + ":"
+ fragmentPagerAdapter.getItemId(position));
}
Sample code for v4 support api.

I think this could help:
class HomePagerAdapter(fragmentManager: FragmentManager) : FragmentStatePagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
private val fragmentConstructors: List<() -> Fragment> by lazy {
listOf(
::AuctionLotsFragment,
::ChatListFragment,
::MarketHomeFragment,
::WalletSectionsFragment,
::SettingsFragment
)
}
private val fragments: HashMap<Int, WeakReference<Fragment>> by lazy {
HashMap()
}
override fun getCount(): Int = fragmentConstructors.size
override fun getItem(position: Int): Fragment {
return fragments[position]?.get() ?: this.createFragmentForPosition(position)
}
private fun createFragmentForPosition(position: Int): Fragment {
val fragment = fragmentConstructors[position].invoke()
fragments[position] = WeakReference(fragment)
return fragment
}
}

Viewpager + FragmentStatePagerAdapter + Fragment not working

I have a FragmentList with some items. If I click an item the appropriate Fragment will open which contains a Viewpager. No problem so far but if I go back to the List and click the item again the method getItem(int position) is not called anymore.
Here a link with a similar problem:
Display fragment viewpager within a fragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
view = inflater.inflate(R.layout.activity_fragment_runtime, container, false);
mViewPager = (ViewPager) view.findViewById(R.id.pager);
indicator = (TitlePageIndicator) view.findViewById(R.id.indicator);
MyFragmentPagerAdapter mMyFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity().getSupportFragmentManager());
mViewPager.setAdapter(mMyFragmentPagerAdapter);
indicator.setViewPager(mViewPager);
return view;
}
class MyFragmentPagerAdapter extends FragmentStatePagerAdapter implements TitleProvider {
public MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public String getTitle(int position) {
return muxbusTitles[position];
}
#Override
public Fragment getItem(int location) {
return muxbusFragmentList.get(location);
}
#Override
public int getCount() {
return muxbusTitles.length;
}
}
return view;
}
Edit:
If someone is interested,the solution was to extends from PagerAdapter instead of FragmentStatePagerAdpater because the Viewpager is already in a Fragment..

I did have similar problem and after scratching my head for quite some time i made an my own understanding (assumption) that ViewPager is keeping the reference of its child fragments into memory even the hosted Fragment or Activity is destroyed (didn't tested with Activity). So i wrote this method freeFragmentsFromViewPager(). You need to call it from onDestroy() of your Fragment.
/**
* This method free the child fragments from ViewPager as ViewPager keeps the reference
* of child fragments into memory and next time when you again come to visit view pager it won't show the fragment layout
* because it has the reference to the fragment whilst the fragment's view was already destroyed.
*/
private void freeFragmentsFromViewPager()
{
for(int i = 0; i < TabsFragmentPagerAdapter.fragments.length; i++)
{
Fragment fragment = TabsFragmentPagerAdapter.fragments[i];
if(fragment != null)
{
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.remove(fragment);
fragmentTransaction.commit();
TabsFragmentPagerAdapter.fragments[i] = null;
}
}
}
And this is my Adapter code
public class TabsFragmentPagerAdapter extends FragmentPagerAdapter
{
public static final int NUM_TABS = 3;
public static Fragment[] fragments = new Fragment[NUM_TABS];
public TabsFragmentPagerAdapter(FragmentManager fm)
{
super(fm);
}
#Override
public Fragment getItem(int position)
{
Log.e("TabsFragmentPagerAdapter", "getItem");
Fragment fragment = TabsFragmentFactory.newInstace(position);
fragments[position] = fragment;
return fragment;
}
#Override
public int getCount()
{
return NUM_TABS;
}
#Override
public CharSequence getPageTitle(int position)
{
return TabsFragmentFactory.getName(position);
}