Develop Reference

onTabSelected FragmentTransaction show not showing

So when I first start up my activity the code will populate each tab, and the actionBar.addTab(tab,true) will call on TabSelected which will then add each fragment. When I physically click on a tab it should then just call fragmentTransaction.Show() and show the fragment. I just get blank. Any idea?
Here is the onCreate code:
// missing some #override stuff etc.
public void onCreate {
mSectionsPagerAdapter = new SectionsPagerAdapter(this.getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
LayoutInflater inflater = LayoutInflater.from(getApplicationContext());
View tabView = inflater.inflate(R.layout.tab_title, null);
TextView titleTV = (TextView) tabView.findViewById(R.id.action_custom_title);
titleTV.setText(mSectionsPagerAdapter.getPageTitle(i));
titleTV.setSingleLine();
titleTV.setTextSize(13);
Tab t = actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this);
t.setCustomView(tabView);
actionBar.addTab(t, true);
}
}
#Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
Bundle b = new Bundle();
switch (tab.getPosition()){
case 0:
b.putString("show", getString(R.string.title_section1));
if (mShowFragment1 == null) {
mShowFragment1 = EpisodeTileFragment.instantiate(this, EpisodeTileFragment.class.getName());
mShowFragment1.setArguments(b);
ft.add(android.R.id.content, mShowFragment1);
addFragmentToActiveList(mShowFragment1);
} else {
ft.show(mShowFragment1);
}
ft.show(mShowFragment1);
break;
case 1:
b.putString("show", getString(R.string.title_section4));
if(mShowFragment3 == null) {
mShowFragment3 = EpisodeTileFragment.newInstance(getString(R.string.title_section4));
ft.add(android.R.id.content, mShowFragment3);
}
mShowFragment3.getArguments().putAll(b);
ft.show(mShowFragment3);
break;
}
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
if(position == 0 || position == 1) {
return EpisodeTileFragment.newInstance(getString(R.string.title_section1));
} else {
return PlaceholderFragment.newInstance(position + 1);
}
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
return "test";
}
}

you're calling the wrong method. FragmentTransaction.show works only for a fragment that has been already attached and that is just hidden.
What you're looking for is fragmentTransaction.commit()
At the same time you might want to replace() the current shown fragment instead of adding a new one to the existing container.
So, just to summarize:
ft.replace(id, fragment).commit();

ViewPager, FragmentStatePagerAdapter and Infinite Scrolling

What I'm trying to achieve:
An Activity with a ViewPager that displays Fragments for a list of Objects in the Adapter (FragmentStatePagerAdapter).
Initially the Activity loads N (lets say 5) objects from the SQLite DB into the Adapter. These objects are chosen with some randomness.
When the user is reaching the end of the list, the activity shall load M (let M be 3) more objects from the DB, add them to the adapter and call notifyDataSetChanged(). When adding them, I check if the new Objects already exist in the list and if they do, the pre-existing one gets removed and the loaded one gets added to the list's tail.
Thus, I'm trying to achieve something like an infinite scrolling ViewPager (NOT a "circular" ViewPager as I want new Objects to be fetched constantly, instead of going back to the begging of the list).
I have some working code and included a sample for the pattern I'm following down bellow. However, I keep getting this exception and have no idea why:
IllegalStateException: Fragment MyObjectFragment{id...} is not currently in the FragmentManager
at android.app.FragmentManagerImpl.saveFragmentInstanceState(FragmentManager.java:553)
at android.support.v13.app.FragmentStatePagerAdapter.destroyItem(FragmentStatePagerAdapter.java:140)
at android.support.v4.ViewPager.populate(ViewPager.java:1002)
...
Code Sample:
The Activity:
public class MyActivitty extends FragmentActivity {
public MyPagerAdapter adapter;
public ViewPager pager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_acyivity_layout);
pager = (ViewPager) findViewById(R.id.viewPager);
ArrayList<MyObject> myObjects = new ArrayList<MyObject>();
// loadInitialObjectsFromDB(int N) goes to SQLite DB and loads the N first objects to show on the ViewPager...
myObjects = loadInitialObjectsFromDB(5);
// Adapter will use the previously fetched objects
adapter = new MyPagerAdapter(this, getFragmentManager(), myObjects);
pager.setAdapter(adapter);
pager.setOffscreenPageLimit(2);
// (...)
}
// (...)
}
The PagerAdapter:
public class MyPagerAdapter extends FragmentStatePagerAdapter implements
ViewPager.OnPageChangeListener {
private MyActivity context;
private ArrayList<MyObject> objectList;
private int currentPosition = 0;
// (...)
public MyPagerAdapter(MyActivity context, FragmentManager fragmentManager, ArrayList<MyObject> objects)
{
super(fragmentManager);
this.context = context;
this.objectList = objects;
}
#Override
public Fragment getItem(int position)
{
MyObject object = objectList.get(position);
return MyObjectFragment.newInstance(position, object);
}
#Override
public int getItemPosition(Object object){
MyObjectFragment frag = (MyObjectFragment) object;
MyObject object = frag.getMyObject();
for(int i = 0; i < objectList.size(); i++)
{
if(objectList.get(i).getId() == object.getId())
{
return i;
}
}
return PagerAdapter.POSITION_NONE;
}
#Override
public int getCount()
{
return objectList.size();
}
#Override
public void onPageSelected(int position)
{
currentPosition = position;
}
// (...)
}
#Override
public void onPageScrollStateChanged(int state)
{
switch(state)
{
case ViewPager.SCROLL_STATE_DRAGGING:
// (...)
break;
case ViewPager.SCROLL_STATE_IDLE:
// if we are reaching the "end" of the list (while scrolling to the right), load more objects
if(currentPosition <= position && position >= answerList.size()-1)
{
// Function in MyActivity that fetches N more objects.
// and adds them to this adapter's ArrayList<MyObject> objectList
// it checks for duplicates so that if the fetched object was already in the back of the list, it is shown again
context.getMoreObjects(3);
notifyDataSetChanged();
}
getMoreQuestions(currentPosition);
case ViewPager.SCROLL_STATE_SETTLING:
break;
}
}
My Fragment:
public class MyObjectFragment extends Fragment {
// Object to represent
private MyObject object;
public static Fragment newInstance(MyActivity context,
int position, MyObject object) {
MyObjectFragment frag = new MyObjectFragment();
Bundle args = new Bundle();
args.putParcelable("Object", object);
frag.setArguments(args);
return frag;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
this.currentInflater = inflater;
final View rootView = inflater.inflate(
R.layout.fragment_my_object, container, false);
// get object from Bundle, set UI, events, etc...
}
// (...)
}
Any idea on why am I getting this Exception? It seems like the FragmentStatePagerAdapter is trying to destroy an item that no longer exists, but I don't understand why.
EDIT 1:
If I comment my #Override getItemPosition(Object object), I don't get the exception anymore. However, I need to override getItemPosition because there is a use case in which the user deletes the currently shown Object causing it to disappear from the adapter's array and forcing the getItemPosition to return POSITION_NONE if the item doesn't exist anymore.
EDIT 2:
Now I do know that this exception only happens when I remove items from my adapter's objectList. I have two situations where MyObject instances are deleted from the objectList:
When the getMoreObjects() adds fetches an object from the DB that was already in the objectList, I delete it and re-add it to the head of the list. I do this to avoid having objects with the same Id in the objectList, as their Id is used by the getItemPosition() to know if they exist and their position.
Before returning, getMoreObjects(), removes the N first objects from the list. I do know that the FragmentStatePagerAdapter already saves memory by only keeping in memory fragments for some of the objects, but I still would like to avoid growing my objectList too much. For now, I have this line commented, as it's not that important.

Solved with the help of this question which itself points at this issue.
FragmentStatePagerAdapter caches the fragments and their saved states in two ArrayLists: mFragments and mSavedState. But when the fragments' order changes (as could happen in my case), there's no mechanism for reordering the elements of mFragments and mSavedState. Therefore, the adapter will provide the wrong fragments to the pager.
I've adapted the code provided in that and changed the import from app.support.v4.Fragment to android.app.Fragment.
public abstract class MyFragmentStatePagerAdapter extends PagerAdapter {
private static final String TAG = "FragmentStatePagerAdapter";
private static final boolean DEBUG = true;
private final FragmentManager mFragmentManager;
private FragmentTransaction mCurTransaction = null;
private long[] mItemIds = new long[] {};
private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
private Fragment mCurrentPrimaryItem = null;
public MyFragmentStatePagerAdapter(FragmentManager fm) {
mFragmentManager = fm;
mItemIds = new long[getCount()];
for (int i = 0; i < mItemIds.length; i++) {
mItemIds[i] = getItemId(i);
}
}
/**
* Return the Fragment associated with a specified position.
*/
public abstract Fragment getItem(int position);
/**
* Return a unique identifier for the item at the given position.
*/
public int getItemId(int position) {
return position;
}
#Override
public void notifyDataSetChanged() {
long[] newItemIds = new long[getCount()];
for (int i = 0; i < newItemIds.length; i++) {
newItemIds[i] = getItemId(i);
}
if (!Arrays.equals(mItemIds, newItemIds)) {
ArrayList<Fragment.SavedState> newSavedState = new ArrayList<Fragment.SavedState>();
ArrayList<Fragment> newFragments = new ArrayList<Fragment>();
for (int oldPosition = 0; oldPosition < mItemIds.length; oldPosition++) {
int newPosition = POSITION_NONE;
for (int i = 0; i < newItemIds.length; i++) {
if (mItemIds[oldPosition] == newItemIds[i]) {
newPosition = i;
break;
}
}
if (newPosition >= 0) {
if (oldPosition < mSavedState.size()) {
Fragment.SavedState savedState = mSavedState.get(oldPosition);
if (savedState != null) {
while (newSavedState.size() <= newPosition) {
newSavedState.add(null);
}
newSavedState.set(newPosition, savedState);
}
}
if (oldPosition < mFragments.size()) {
Fragment fragment = mFragments.get(oldPosition);
if (fragment != null) {
while (newFragments.size() <= newPosition) {
newFragments.add(null);
}
newFragments.set(newPosition, fragment);
}
}
}
}
mItemIds = newItemIds;
mSavedState = newSavedState;
mFragments = newFragments;
}
super.notifyDataSetChanged();
}
#Override
public void startUpdate(ViewGroup container) {
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
// If we already have this item instantiated, there is nothing
// to do. This can happen when we are restoring the entire pager
// from its saved state, where the fragment manager has already
// taken care of restoring the fragments we previously had instantiated.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
return f;
}
}
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
Fragment fragment = getItem(position);
if (DEBUG) Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
if (mSavedState.size() > position) {
Fragment.SavedState fss = mSavedState.get(position);
if (fss != null) {
fragment.setInitialSavedState(fss);
}
}
while (mFragments.size() <= position) {
mFragments.add(null);
}
fragment.setMenuVisibility(false);
mFragments.set(position, fragment);
mCurTransaction.add(container.getId(), fragment);
return fragment;
}
public void destroyItemState(int position) {
mFragments.remove(position);
mSavedState.remove(position);
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment) object;
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
//position = getItemPosition(object);
if (DEBUG) Log.v(TAG, "Removing item #" + position + ": f=" + object
+ " v=" + ((Fragment)object).getView());
if (position >= 0) {
while (mSavedState.size() <= position) {
mSavedState.add(null);
}
mSavedState.set(position, mFragmentManager.saveFragmentInstanceState(fragment));
if(position < mFragments.size()){
mFragments.set(position, null);
}
}
mCurTransaction.remove(fragment);
}
#Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment)object;
if (fragment != mCurrentPrimaryItem) {
if (mCurrentPrimaryItem != null) {
mCurrentPrimaryItem.setMenuVisibility(false);
}
if (fragment != null) {
fragment.setMenuVisibility(true);
}
mCurrentPrimaryItem = fragment;
}
}
#Override
public void finishUpdate(ViewGroup container) {
if (mCurTransaction != null) {
mCurTransaction.commitAllowingStateLoss();
mCurTransaction = null;
mFragmentManager.executePendingTransactions();
}
}
#Override
public boolean isViewFromObject(View view, Object object) {
return ((Fragment)object).getView() == view;
}
#Override
public Parcelable saveState() {
Bundle state = new Bundle();
if (mItemIds.length > 0) {
state.putLongArray("itemids", mItemIds);
}
if (mSavedState.size() > 0) {
Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()];
mSavedState.toArray(fss);
state.putParcelableArray("states", fss);
}
for (int i=0; i<mFragments.size(); i++) {
Fragment f = mFragments.get(i);
if (f != null) {
String key = "f" + i;
mFragmentManager.putFragment(state, key, f);
}
}
return state;
}
#Override
public void restoreState(Parcelable state, ClassLoader loader) {
if (state != null) {
Bundle bundle = (Bundle)state;
bundle.setClassLoader(loader);
mItemIds = bundle.getLongArray("itemids");
if (mItemIds == null) {
mItemIds = new long[] {};
}
Parcelable[] fss = bundle.getParcelableArray("states");
mSavedState.clear();
mFragments.clear();
if (fss != null) {
for (int i=0; i<fss.length; i++) {
mSavedState.add((Fragment.SavedState)fss[i]);
}
}
Iterable<String> keys = bundle.keySet();
for (String key: keys) {
if (key.startsWith("f")) {
int index = Integer.parseInt(key.substring(1));
Fragment f = mFragmentManager.getFragment(bundle, key);
if (f != null) {
while (mFragments.size() <= index) {
mFragments.add(null);
}
f.setMenuVisibility(false);
mFragments.set(index, f);
} else {
Log.w(TAG, "Bad fragment at key " + key);
}
}
}
}
}
}
Credit for the original code goes to user #UgglyNoodle.
Then, instead of using FragmentStatePagerAdapter I use the MyFragmentStatePagerAdapter from above and override getItemPosition() and getItemId() consistently with getItem().

visibility issue in ViewPager in SherlockFragments while scrolling (in gingerbread)

I have used ViewPager for scrolling among the fragments.
While testing on gingerbread there is a strange issue-
After scrolling first two tabs, the visibility of all fragments GONE completely
This continues until I change the orientation.
This issue occurs only at start in gingerbread devices only. It is working fine on ICS and others.
here is the code of TabsAdapter
/**
* This is a helper class that implements the management of tabs and all
* details of connecting a ViewPager with associated TabHost. It relies on a
* trick. Normally a tab host has a simple API for supplying a View or
* Intent that each tab will show. This is not sufficient for switching
* between pages. So instead we make the content part of the tab host 0dp
* high (it is not shown) and the TabsAdapter supplies its own dummy view to
* show as the tab content. It listens to changes in tabs, and takes care of
* switch to the correct paged in the ViewPager whenever the selected tab
* changes.
*/
private class TabsAdapter extends FragmentPagerAdapter implements
ViewPager.OnPageChangeListener, ActionBar.TabListener {
private final Context mContext;
private final ActionBar mActionBar;
private final ViewPager mViewPager;
private final List<String> mTabs = new ArrayList<String>();
private final List<Integer> mTabsId = new ArrayList<Integer>();
private boolean hasClearedDetails = false;
private int mCurrentPosition = -1;
/**
* Used during page migration, to remember the next position
* {#link #onPageSelected(int)} specified.
*/
private int mNextPosition = -1;
public TabsAdapter(FragmentActivity activity, ActionBar actionBar, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mActionBar = actionBar;
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
public void addTab(ActionBar.Tab tab, Class<?> clss, int tabId) {
mTabs.add(clss.getName());
mTabsId.add(tabId);
mActionBar.addTab(tab.setTabListener(this));
notifyDataSetChanged();
}
public void removeTabAt(int location) {
mTabs.remove(location);
mTabsId.remove(location);
mActionBar.removeTabAt(location);
notifyDataSetChanged();
}
public Integer getIdForPosition(int position) {
if(position >= 0 && position < mTabsId.size()) {
return mTabsId.get(position);
}
return null;
}
public Integer getPositionForId(int id) {
int fPos = mTabsId.indexOf(id);
if(fPos >= 0) {
return fPos;
}
return null;
}
#Override
public int getCount() {
return mTabs.size();
}
#Override
public Fragment getItem(int position) {
return Fragment.instantiate(mContext, mTabs.get(position), new Bundle());
}
#Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
clearDetails();
if (mViewPager.getCurrentItem() != tab.getPosition()) {
Log.e(THIS_FILE+"Anurag debugging","ISSUE HERE");
mViewPager.setCurrentItem(tab.getPosition(), true);
}
}
#Override
public void onPageSelected(int position) {
mActionBar.setSelectedNavigationItem(position);
if (mCurrentPosition == position) {
Log.w(THIS_FILE, "Previous position and next position became same (" + position
+ ")");
Log.e(THIS_FILE, "Previous position and next position became same (" + position
+ ")");
}
mNextPosition = position;
}
#Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// Nothing to do
}
#Override
public int getItemPosition(Object object){
return mCurrentPosition;
}
#Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// Nothing to do
}
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
// Nothing to do
}
#Override
public void onPageScrollStateChanged(int state) {
switch (state) {
case ViewPager.SCROLL_STATE_IDLE: {
Log.e(THIS_FILE, "SCROLL_STATE_IDLE"+mCurrentPosition);
if (mCurrentPosition >= 0) {
sendFragmentVisibilityChange(mCurrentPosition, false);
}
if (mNextPosition >= 0) {
sendFragmentVisibilityChange(mNextPosition, true);
}
invalidateOptionsMenu();
mCurrentPosition = mNextPosition;
break;
}
case ViewPager.SCROLL_STATE_DRAGGING:
Log.e(THIS_FILE, "SCROLL_STATE_DRAGGING");
clearDetails();
hasClearedDetails = true;
break;
case ViewPager.SCROLL_STATE_SETTLING:
Log.e(THIS_FILE, "SCROLL_STATE_SETTLING");
hasClearedDetails = false;
break;
default:
break;
}
}
private void clearDetails() {
if (mDualPane && !hasClearedDetails) {
Log.e(THIS_FILE, "check in clear detalis");
FragmentTransaction ft = SipHome.this.getSupportFragmentManager()
.beginTransaction();
ft.replace(R.id.details, new Fragment(), null);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
ft.commit();
}
}
}
The code for sendFragmentVisibilityChange is
private void sendFragmentVisibilityChange(int position, boolean visibility) {
try {
final Fragment fragment = getFragmentAt(position);
if (fragment instanceof ViewPagerVisibilityListener) {
((ViewPagerVisibilityListener) fragment).onVisibilityChanged(visibility);
}
}catch(IllegalStateException e) {
Log.e(THIS_FILE, "Fragment not anymore managed");
e.printStackTrace();
}catch(Exception e) {
Log.e(THIS_FILE, "Fragment not anymore managed");
e.printStackTrace();
}
}
Fragments are calling onVisibilityChanged to perform some operation on scrolling.
The fragments extends SherlockFragment.
thanks in advance

set the OffscreenPageLimit of your ViewPager to number of Views your ViewPager actually holds using setoffscreenpagelimit(int count).

Android, How to mix ActionBar.Tab + View Pager + ListFragment

I've been trying to test how to mix all these things together and I'm having problems!!
I just want an app with three tabs using the ActionBar.Tab. For example, this tabs can be movies genres Action, Adventure and Animation, the user can swipe through the tabs, so it will use the ViewPager and each tab will show a list of movies of that genre. There's no need to have three different fragments classes because all tabs will be the same format a simple list.
And I'm having problems because when I select the second tab, the position for onPageSelected is 1,
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mCollectionPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
mActionBar.setSelectedNavigationItem(position);
}
});
This causes the call to the method public Fragment getItem(int i) inside the CollectionPagerAdapter class, but then the value of i is 2 NOT 1, so then it calls the createView for the TabFragment class with a value of 2 NOT 1, so tabs are not refreshing successfully.
Any help will be really appreciated!!
Code to create the tabs,
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mCollectionPagerAdapter.getCount(); i++) {
mActionBar.addTab(mActionBar.newTab()
.setText(mGenres.get(i).getName())
.setTabListener(this));
//Let's request the movies for the first three genres
new GetMoviesByGenre().execute(mGenres.get(i).getId());
}
When a tab is selected,
#Override
public void onTabSelected(ActionBar.Tab tab, android.app.FragmentTransaction arg1) {
//Let's update the dataset for the selected genre
TabFragment fragment =
(TabFragment) getSupportFragmentManager().findFragmentByTag(
"android:switcher:"+R.id.pager+":"+tab.getPosition());
if(fragment != null) // could be null if not instantiated yet
{
if(fragment.getView() != null)
{
fragment.updateDisplay(tab.getPosition()); // do what updates are required
}
}
mViewPager.setCurrentItem(tab.getPosition());
}
CollectionPageAdapter class
public class CollectionPagerAdapter extends FragmentPagerAdapter {
final int NUM_ITEMS = 3; // number of tabs
List<Fragment> fragments = new ArrayList<Fragment>();
public Fragment getItem(int pos) {
return fragments.get(pos);
}
public void addFragment(Fragment f) {
fragments.add(f);
}
public CollectionPagerAdapter(FragmentManager fm) {
super(fm);
//Let's add the fragments
for (int i=0;i<NUM_ITEMS;i++)
{
Fragment fragment = new TabFragment();
Bundle args = new Bundle();
args.putInt(TabFragment.ARG_OBJECT, 0);
fragment.setArguments(args);
addFragment (fragment);
}
}
#Override
public int getCount() {
return NUM_ITEMS;
}
}
TabFragment class
public class TabFragment extends ListFragment {
public static final String ARG_OBJECT = "object";
private MoviesAdapter m_Adapter;
private ArrayList <Movie> mMovies = new ArrayList<Movie>();
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// you only need to instantiate these the first time your fragment is
// created; then, the method above will do the rest
if (m_Adapter == null) {
m_Adapter = new MoviesAdapter(getActivity(), mMovies);
}
setListAdapter(m_Adapter);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
int position = getArguments().getInt(ARG_OBJECT); // to check is the right fragment
View rootView = inflater.inflate(R.layout.tabs, container, false);
return rootView;
}
public void updateDisplay (int type)
{
GlobalVars gv = (GlobalVars)getActivity().getApplicationContext();
switch (type)
{
case 0:
mMovies = gv.getActionMovies();
break;
case 1:
mMovies = gv.getAdventureMovies();
break;
case 2:
mMovies = gv.getAnimationMovies();
break;
}
m_Adapter.notifyDataSetChanged();
}
}
I don't what I'm doing wrong, I guess that the fragments are messed up, because when I press the second tab, data from the first tab is updated, and so on ...
Thanks!

Instead of using CollectionPageAdapter, I changed to use the TabsAdapter class shown in Android documentation of ViewPager and it works!
public class TabsAdapter extends FragmentPagerAdapter
implements ActionBar.TabListener, ViewPager.OnPageChangeListener {
private final Context mContext;
private final ActionBar mActionBar;
private final ViewPager mViewPager;
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
private final List<Fragment> fragments = new ArrayList<Fragment>();
static final class TabInfo {
private final Class<?> clss;
private final Bundle args;
TabInfo(Class<?> _class, Bundle _args) {
clss = _class;
args = _args;
}
}
public TabsAdapter(FragmentActivity activity, ViewPager pager) {
super(activity.getSupportFragmentManager());
mContext = activity;
mActionBar = activity.getActionBar();
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) {
TabInfo info = new TabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
mActionBar.addTab(tab);
notifyDataSetChanged();
}
#Override
public int getCount() {
return mTabs.size();
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
#Override
public Fragment getItem(int position) {
TabInfo info = mTabs.get(position);
Fragment fr = Fragment.instantiate(mContext, info.clss.getName(), info.args);
//addFragment (fr, position);
return fr;
}
public void addFragment(Fragment f, int location) {
if (fragments.size() == 0)
fragments.add(f);
else
fragments.add(location, f);
}
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
mActionBar.setSelectedNavigationItem(position);
}
#Override
public void onPageScrollStateChanged(int state) {
}
#Override
public void onTabSelected(Tab tab, android.app.FragmentTransaction ft) {
Object tag = tab.getTag();
for (int i=0; i<mTabs.size(); i++) {
if (mTabs.get(i) == tag) {
updateDatasetMovies (i);
mViewPager.setCurrentItem(i);
}
}
}
#Override
public void onTabReselected(Tab tab, android.app.FragmentTransaction ft) {
// TODO Auto-generated method stub
}
#Override
public void onTabUnselected(Tab tab, android.app.FragmentTransaction ft) {
// TODO Auto-generated method stub
}
public void updateDatasetMovies (int pos)
{
//Let's update the dataset for the selected genre
TabFragment fragment =
(TabFragment) ((FragmentActivity)mContext).getSupportFragmentManager().findFragmentByTag(
"android:switcher:"+R.id.pager+":"+pos);
//TabFragment fragment = (TabFragment) getItem(pos);
if(fragment != null) // could be null if not instantiated yet
{
if(fragment.getView() != null)
{
// no need to call if fragment's onDestroyView()
//has since been called.
fragment.updateDisplay(pos); // do what updates are required
}
}
}
}`

I agree with nirvik on this, however there is one cruciual improvement that should be made. This implementation has one flaw - when swiping to a next fragment the onPageSelected method is invoked, which in turn invokes onTabSelected method by calling mActionBar.setSelectedNavigationItem(position);. This causes a flicker in the animation.
This:
viewPager.setCurrentItem(i);
should be replaced by this:
if(i != viewPager.getCurrentItem()) {
viewPager.setCurrentItem(i);
}
resulting in a smooth transition.

You can try including the following code in your FragmentPagerAdapter and see if this addresses the issue.
public int getItemPosition(Object object) {
return POSITION_NONE;
}
You could also try using a FragmentStatePagerAdapter.

Remove Fragment Page from ViewPager in Android

I'm trying to dynamically add and remove Fragments from a ViewPager, adding works without any problems, but removing doesn't work as expected.
Everytime I want to remove the current item, the last one gets removed.
I also tried to use an FragmentStatePagerAdapter or return POSITION_NONE in the adapter's getItemPosition method.
What am I doing wrong?
Here's a basic example:
MainActivity.java
public class MainActivity extends FragmentActivity implements TextProvider {
private Button mAdd;
private Button mRemove;
private ViewPager mPager;
private MyPagerAdapter mAdapter;
private ArrayList<String> mEntries = new ArrayList<String>();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mEntries.add("pos 1");
mEntries.add("pos 2");
mEntries.add("pos 3");
mEntries.add("pos 4");
mEntries.add("pos 5");
mAdd = (Button) findViewById(R.id.add);
mRemove = (Button) findViewById(R.id.remove);
mPager = (ViewPager) findViewById(R.id.pager);
mAdd.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View view) {
addNewItem();
}
});
mRemove.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View view) {
removeCurrentItem();
}
});
mAdapter = new MyPagerAdapter(this.getSupportFragmentManager(), this);
mPager.setAdapter(mAdapter);
}
private void addNewItem() {
mEntries.add("new item");
mAdapter.notifyDataSetChanged();
}
private void removeCurrentItem() {
int position = mPager.getCurrentItem();
mEntries.remove(position);
mAdapter.notifyDataSetChanged();
}
#Override
public String getTextForPosition(int position) {
return mEntries.get(position);
}
#Override
public int getCount() {
return mEntries.size();
}
private class MyPagerAdapter extends FragmentPagerAdapter {
private TextProvider mProvider;
public MyPagerAdapter(FragmentManager fm, TextProvider provider) {
super(fm);
this.mProvider = provider;
}
#Override
public Fragment getItem(int position) {
return MyFragment.newInstance(mProvider.getTextForPosition(position));
}
#Override
public int getCount() {
return mProvider.getCount();
}
}
}
TextProvider.java
public interface TextProvider {
public String getTextForPosition(int position);
public int getCount();
}
MyFragment.java
public class MyFragment extends Fragment {
private String mText;
public static MyFragment newInstance(String text) {
MyFragment f = new MyFragment(text);
return f;
}
public MyFragment() {
}
public MyFragment(String text) {
this.mText = text;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment, container, false);
((TextView) root.findViewById(R.id.position)).setText(mText);
return root;
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<Button
android:id="#+id/add"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="add new item" />
<Button
android:id="#+id/remove"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="remove current item" />
<android.support.v4.view.ViewPager
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1" />
</LinearLayout>
fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="#+id/position"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:textSize="35sp" />
</LinearLayout>

The ViewPager doesn't remove your fragments with the code above because it loads several views (or fragments in your case) into memory. In addition to the visible view, it also loads the view to either side of the visible one. This provides the smooth scrolling from view to view that makes the ViewPager so cool.
To achieve the effect you want, you need to do a couple of things.
Change the FragmentPagerAdapter to a FragmentStatePagerAdapter. The reason for this is that the FragmentPagerAdapter will keep all the views that it loads into memory forever. Where the FragmentStatePagerAdapter disposes of views that fall outside the current and traversable views.
Override the adapter method getItemPosition (shown below). When we call mAdapter.notifyDataSetChanged(); the ViewPager interrogates the adapter to determine what has changed in terms of positioning. We use this method to say that everything has changed so reprocess all your view positioning.
And here's the code...
private class MyPagerAdapter extends FragmentStatePagerAdapter {
//... your existing code
#Override
public int getItemPosition(Object object){
return PagerAdapter.POSITION_NONE;
}
}

The solution by Louth was not enough to get things working for me, as the existing fragments were not getting destroyed. Motivated by this answer, I found that the solution is to override the getItemId(int position) method of FragmentPagerAdapter to give a new unique ID whenever there has been a change in the expected position of a Fragment.
Source Code:
private class MyPagerAdapter extends FragmentPagerAdapter {
private TextProvider mProvider;
private long baseId = 0;
public MyPagerAdapter(FragmentManager fm, TextProvider provider) {
super(fm);
this.mProvider = provider;
}
#Override
public Fragment getItem(int position) {
return MyFragment.newInstance(mProvider.getTextForPosition(position));
}
#Override
public int getCount() {
return mProvider.getCount();
}
//this is called when notifyDataSetChanged() is called
#Override
public int getItemPosition(Object object) {
// refresh all fragments when data set changed
return PagerAdapter.POSITION_NONE;
}
#Override
public long getItemId(int position) {
// give an ID different from position when position has been changed
return baseId + position;
}
/**
* Notify that the position of a fragment has been changed.
* Create a new ID for each position to force recreation of the fragment
* #param n number of items which have been changed
*/
public void notifyChangeInPosition(int n) {
// shift the ID returned by getItemId outside the range of all previous fragments
baseId += getCount() + n;
}
}
Now, for example if you delete a single tab or make some change to the order, you should call notifyChangeInPosition(1) before calling notifyDataSetChanged(), which will ensure that all the Fragments will be recreated.
Why this solution works
Overriding getItemPosition():
When notifyDataSetChanged() is called, the adapter calls the notifyChanged() method of the ViewPager which it is attached to. The ViewPager then checks the value returned by the adapter's getItemPosition() for each item, removing those items which return POSITION_NONE (see the source code) and then repopulating.
Overriding getItemId():
This is necessary to prevent the adapter from reloading the old fragment when the ViewPager is repopulating. You can easily understand why this works by looking at the source code for instantiateItem() in FragmentPagerAdapter.
final long itemId = getItemId(position);
// Do we already have this fragment?
String name = makeFragmentName(container.getId(), itemId);
Fragment fragment = mFragmentManager.findFragmentByTag(name);
if (fragment != null) {
if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
mCurTransaction.attach(fragment);
} else {
fragment = getItem(position);
if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
mCurTransaction.add(container.getId(), fragment,
makeFragmentName(container.getId(), itemId));
}
As you can see, the getItem() method is only called if the fragment manager finds no existing fragments with the same Id. To me it seems like a bug that the old fragments are still attached even after notifyDataSetChanged() is called, but the documentation for ViewPager does clearly state that:
Note this class is currently under early design and development. The API will likely change in later updates of the compatibility library, requiring changes to the source code of apps when they are compiled against the newer version.
So hopefully the workaround given here will not be necessary in a future version of the support library.

my working solution to remove fragment page from view pager
public class MyFragmentAdapter extends FragmentStatePagerAdapter {
private ArrayList<ItemFragment> pages;
public MyFragmentAdapter(FragmentManager fragmentManager, ArrayList<ItemFragment> pages) {
super(fragmentManager);
this.pages = pages;
}
#Override
public Fragment getItem(int index) {
return pages.get(index);
}
#Override
public int getCount() {
return pages.size();
}
#Override
public int getItemPosition(Object object) {
int index = pages.indexOf (object);
if (index == -1)
return POSITION_NONE;
else
return index;
}
}
And when i need to remove some page by index i do this
pages.remove(position); // ArrayList<ItemFragment>
adapter.notifyDataSetChanged(); // MyFragmentAdapter
Here it is my adapter initialization
MyFragmentAdapter adapter = new MyFragmentAdapter(getSupportFragmentManager(), pages);
viewPager.setAdapter(adapter);

The fragment must be already removed but the issue was viewpager save state
Try
myViewPager.setSaveFromParentEnabled(false);
Nothing worked but this solved the issue !
Cheers !

I had the idea of simply copy the source code from android.support.v4.app.FragmentPagerAdpater into a custom class named
CustumFragmentPagerAdapter. This gave me the chance to modify the instantiateItem(...) so that every time it is called, it removes / destroys the currently attached fragment before it adds the new fragment received from getItem() method.
Simply modify the instantiateItem(...) in the following way:
#Override
public Object instantiateItem(ViewGroup container, int position) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
final long itemId = getItemId(position);
// Do we already have this fragment?
String name = makeFragmentName(container.getId(), itemId);
Fragment fragment = mFragmentManager.findFragmentByTag(name);
// remove / destroy current fragment
if (fragment != null) {
mCurTransaction.remove(fragment);
}
// get new fragment and add it
fragment = getItem(position);
mCurTransaction.add(container.getId(), fragment, makeFragmentName(container.getId(), itemId));
if (fragment != mCurrentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}

You can combine both for better :
private class MyPagerAdapter extends FragmentStatePagerAdapter {
//... your existing code
#Override
public int getItemPosition(Object object){
if(Any_Reason_You_WantTo_Update_Positions) //this includes deleting or adding pages
return PagerAdapter.POSITION_NONE;
}
else
return PagerAdapter.POSITION_UNCHANGED; //this ensures high performance in other operations such as editing list items.
}

I had some problems with FragmentStatePagerAdapter.
After removing an item:
there was another item used for a position (an item which did not belong to the position but to a position next to it)
or some fragment was not loaded (there was only blank background visible on that page)
After lots of experiments, I came up with the following solution.
public class SomeAdapter extends FragmentStatePagerAdapter {
private List<Item> items = new ArrayList<Item>();
private boolean removing;
#Override
public Fragment getItem(int position) {
ItemFragment fragment = new ItemFragment();
Bundle args = new Bundle();
// use items.get(position) to configure fragment
fragment.setArguments(args);
return fragment;
}
#Override
public int getCount() {
return items.size();
}
#Override
public int getItemPosition(Object object) {
if (removing) {
return PagerAdapter.POSITION_NONE;
}
Item item = getItemOfFragment(object);
int index = items.indexOf(item);
if (index == -1) {
return POSITION_NONE;
} else {
return index;
}
}
public void addItem(Item item) {
items.add(item);
notifyDataSetChanged();
}
public void removeItem(int position) {
items.remove(position);
removing = true;
notifyDataSetChanged();
removing = false;
}
}
This solution only uses a hack in case of removing an item. Otherwise (e.g. when adding an item) it retains the cleanliness and performance of an original code.
Of course, from the outside of the adapter, you call only addItem/removeItem, no need to call notifyDataSetChanged().

For future readers!
Now you can use ViewPager2 for dynamically adding, removing fragment from the viewpager.
Quoting form API reference
ViewPager2 replaces ViewPager, addressing most of its predecessor’s
pain-points, including right-to-left layout support, vertical
orientation, modifiable Fragment collections, etc.
Take look at MutableCollectionFragmentActivity.kt in googlesample/android-viewpager2 for an example of adding, removing fragments dynamically from the viewpager.
For your information:
Articles:
Exploring the ViewPager2
Look deep into ViewPager2
API reference
Release notes
Samples Repo: https://github.com/googlesamples/android-viewpager2

Louth's answer works fine. But I don't think always return POSITION_NONE is a good idea. Because POSITION_NONE means that fragment should be destroyed and a new fragment will be created.
You can check that in dataSetChanged function in the source code of ViewPager.
if (newPos == PagerAdapter.POSITION_NONE) {
mItems.remove(i);
i--;
... not related code
mAdapter.destroyItem(this, ii.position, ii.object);
So I think you'd better use an arraylist of weakReference to save all the fragments you have created. And when you add or remove some page, you can get the right position from your own arraylist.
public int getItemPosition(Object object) {
for (int i = 0; i < mFragmentsReferences.size(); i ++) {
WeakReference<Fragment> reference = mFragmentsReferences.get(i);
if (reference != null && reference.get() != null) {
Fragment fragment = reference.get();
if (fragment == object) {
return i;
}
}
}
return POSITION_NONE;
}
According to the comments, getItemPosition is Called when the host view is attempting to determine if an item's position has changed. And the return value means its new position.
But this is not enought. We still have an important step to take.
In the source code of FragmentStatePagerAdapter, there is an array named "mFragments" caches the fragments which are not destroyed. And in instantiateItem function.
if (mFragments.size() > position) {
Fragment f = mFragments.get(position);
if (f != null) {
return f;
}
}
It returned the cached fragment directly when it find that cached fragment is not null. So there is a problem. From example, let's delete one page at position 2, Firstly, We remove that fragment from our own reference arraylist. so in getItemPosition it will return POSITION_NONE for that fragment, and then that fragment will be destroyed and removed from "mFragments".
mFragments.set(position, null);
Now the fragment at position 3 will be at position 2. And instantiatedItem with param position 3 will be called. At this time, the third item in "mFramgents" is not null, so it will return directly. But actually what it returned is the fragment at position 2. So when we turn into page 3, we will find an empty page there.
To work around this problem. My advise is that you can copy the source code of FragmentStatePagerAdapter into your own project, and when you do add or remove operations, you should add and remove elements in the "mFragments" arraylist.
Things will be simpler if you just use PagerAdapter instead of FragmentStatePagerAdapter. Good Luck.

add or remove fragment in viewpager dynamically.
Call setupViewPager(viewPager) on activity start.
To load different fragment call setupViewPagerCustom(viewPager).
e.g. on button click call: setupViewPagerCustom(viewPager);
private void setupViewPager(ViewPager viewPager)
{
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new fragmnet1(), "HOME");
adapter.addFrag(new fragmnet2(), "SERVICES");
viewPager.setAdapter(adapter);
}
private void setupViewPagerCustom(ViewPager viewPager)
{
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new fragmnet3(), "Contact us");
adapter.addFrag(new fragmnet4(), "ABOUT US");
viewPager.setAdapter(adapter);
}
//Viewpageradapter, handles the views
static class ViewPagerAdapter extends FragmentStatePagerAdapter
{
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager){
super(manager);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
#Override
public int getItemPosition(Object object){
return PagerAdapter.POSITION_NONE;
}
public void addFrag(Fragment fragment, String title){
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position){
return mFragmentTitleList.get(position);
}
}

Try this solution. I have used databinding for binding view. You can use common "findViewById()" function.
public class ActCPExpense extends BaseActivity implements View.OnClickListener, {
private static final String TAG = ActCPExpense.class.getSimpleName();
private Context mContext;
private ActCpLossBinding mBinding;
private ViewPagerAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try {
setContentView(R.layout.act_cp_loss);
mBinding = DataBindingUtil.setContentView(this, R.layout.act_cp_loss);
mContext = ActCPExpense.this;
initViewsAct();
} catch (Exception e) {
LogUtils.LOGE(TAG, e);
}
}
private void initViewsAct() {
adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(FragmentCPPayee.newInstance(), "Title");
mBinding.viewpager.setAdapter(adapter);
mBinding.tab.setViewPager(mBinding.viewpager);
}
#Override
public boolean onOptionsItemSelected(MenuItem itemActUtility) {
int i = itemActUtility.getItemId();
if (i == android.R.id.home) {
onBackPressed();
}
return super.onOptionsItemSelected(itemActUtility);
}
#Override
public void onClick(View view) {
super.onClick(view);
int id = view.getId();
if (id == R.id.btnAdd) {
addFragment();
} else if (id == R.id.btnDelete) {
removeFragment();
}
}
private void addFragment(){
adapter.addFragment(FragmentCPPayee.newInstance("Title");
adapter.notifyDataSetChanged();
mBinding.tab.setViewPager(mBinding.viewpager);
}
private void removeFragment(){
adapter.removeItem(mBinding.viewpager.getCurrentItem());
mBinding.tab.setViewPager(mBinding.viewpager);
}
class ViewPagerAdapter extends FragmentStatePagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public int getItemPosition(#NonNull Object object) {
return PagerAdapter.POSITION_NONE;
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
public void removeItem(int pos) {
destroyItem(null, pos, mFragmentList.get(pos));
mFragmentList.remove(pos);
mFragmentTitleList.remove(pos);
adapter.notifyDataSetChanged();
mBinding.viewpager.setCurrentItem(pos - 1, false);
}
#Override
public CharSequence getPageTitle(int position) {
return "Title " + String.valueOf(position + 1);
}
}
}

I added a function "clearFragments" and I used that function to clear adapter before setting the new fragments. This calls the proper remove actions of Fragments. My pagerAdapter class:
private class ChartPagerAdapter extends FragmentPagerAdapter{
private ArrayList<Fragment> fragmentList;
ChartPagerAdapter(FragmentManager fm){
super(fm);
fragmentList = new ArrayList<>();
}
void setFragments(ArrayList<? extends Fragment> fragments){
fragmentList.addAll(fragments);
}
void clearFragments(){
for(Fragment fragment:fragmentList)
getChildFragmentManager().beginTransaction().remove(fragment).commit();
fragmentList.clear();
}
#Override
public Fragment getItem(int i) {
return fragmentList.get(i);
}
#Override
public int getCount() {
return fragmentList.size();
}
}

i solved this problem by these steps
1- use FragmentPagerAdapter
2- in each fragment create a random id
fragment.id = new Random().nextInt();
3- override getItemPosition in adapter
#Override
public int getItemPosition(#NonNull Object object) {
return PagerAdapter.POSITION_NONE;
}
4-override getItemId in adapter
#Override
public long getItemId(int position) {
return mDatasetFragments.get(position).id;
}
5- now delete code is
adapter.mDatasetFragments.remove(< item to delete position >);
adapter.notifyDataSetChanged();
this worked for me i hope help

My final version code, fixed ALL bugs. It took me 3 days
Updated 2020/07/18:
I had changed a lot of the source code and fix so many bugs, but I don't promise it still work today.
https://github.com/lin1987www/FragmentBuilder/blob/master/commonLibrary/src/main/java/android/support/v4/app/FragmentStatePagerAdapterFix.java
public class FragmentStatePagerAdapterFix extends PagerAdapter {
private static final String TAG = FragmentStatePagerAdapterFix.class.getSimpleName();
private static final boolean DEBUG = false;
private WeakReference<FragmentActivity> wrFragmentActivity;
private WeakReference<Fragment> wrParentFragment;
private final FragmentManager mFragmentManager;
private FragmentTransaction mCurTransaction = null;
protected ArrayList<Fragment> mFragments = new ArrayList<>();
protected ArrayList<FragmentState> mFragmentStates = new ArrayList<>();
protected ArrayList<String> mFragmentTags = new ArrayList<>();
protected ArrayList<String> mFragmentClassNames = new ArrayList<>();
protected ArrayList<Bundle> mFragmentArgs = new ArrayList<>();
private Fragment mCurrentPrimaryItem = null;
private boolean[] mTempPositionChange;
#Override
public int getCount() {
return mFragmentClassNames.size();
}
public FragmentActivity getFragmentActivity() {
return wrFragmentActivity.get();
}
public Fragment getParentFragment() {
return wrParentFragment.get();
}
public FragmentStatePagerAdapterFix(FragmentActivity activity) {
mFragmentManager = activity.getSupportFragmentManager();
wrFragmentActivity = new WeakReference<>(activity);
wrParentFragment = new WeakReference<>(null);
}
public FragmentStatePagerAdapterFix(Fragment fragment) {
mFragmentManager = fragment.getChildFragmentManager();
wrFragmentActivity = new WeakReference<>(fragment.getActivity());
wrParentFragment = new WeakReference<>(fragment);
}
public void add(Class<? extends android.support.v4.app.Fragment> fragClass) {
add(fragClass, null, null);
}
public void add(Class<? extends android.support.v4.app.Fragment> fragClass, Bundle args) {
add(fragClass, args, null);
}
public void add(Class<? extends android.support.v4.app.Fragment> fragClass, String tag) {
add(fragClass, null, tag);
}
public void add(Class<? extends android.support.v4.app.Fragment> fragClass, Bundle args, String tag) {
add(fragClass, args, tag, getCount());
}
public void add(Class<? extends android.support.v4.app.Fragment> fragClass, Bundle args, String tag, int position) {
mFragments.add(position, null);
mFragmentStates.add(position, null);
mFragmentTags.add(position, tag);
mFragmentClassNames.add(position, fragClass.getName());
mFragmentArgs.add(position, args);
mTempPositionChange = new boolean[getCount()];
}
public void remove(int position) {
if (position < getCount()) {
mTempPositionChange = new boolean[getCount()];
for (int i = position; i < mTempPositionChange.length; i++) {
mTempPositionChange[i] = true;
}
mFragments.remove(position);
mFragmentStates.remove(position);
mFragmentTags.remove(position);
mFragmentClassNames.remove(position);
mFragmentArgs.remove(position);
}
}
public void clear(){
mFragments.clear();
mFragmentStates.clear();
mFragmentTags.clear();
mFragmentClassNames.clear();
mFragmentArgs.clear();
}
#Override
public void startUpdate(ViewGroup container) {
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment fragment;
// If we already have this item instantiated, there is nothing
// to do. This can happen when we are restoring the entire pager
// from its saved state, where the fragment manager has already
// taken care of restoring the fragments we previously had instantiated.
fragment = mFragments.get(position);
if (fragment != null) {
return fragment;
}
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
FragmentState fs = mFragmentStates.get(position);
if (fs != null) {
fragment = fs.instantiate(getFragmentActivity(), getParentFragment());
// Fix bug
// http://stackoverflow.com/questions/11381470/classnotfoundexception-when-unmarshalling-android-support-v4-view-viewpagersav
if (fragment.mSavedFragmentState != null) {
fragment.mSavedFragmentState.setClassLoader(fragment.getClass().getClassLoader());
}
}
if (fragment == null) {
fragment = Fragment.instantiate(getFragmentActivity(), mFragmentClassNames.get(position), mFragmentArgs.get(position));
}
if (DEBUG) {
Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
}
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
mFragments.set(position, fragment);
mFragmentStates.set(position, null);
mCurTransaction.add(container.getId(), fragment, mFragmentTags.get(position));
return fragment;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment) object;
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
if (DEBUG) {
Log.v(TAG, "Removing item #" + position + ": f=" + object
+ " v=" + ((Fragment) object).getView());
}
if (position < getCount()) {
FragmentState fragmentState = new FragmentState(fragment);
Fragment.SavedState savedState = mFragmentManager.saveFragmentInstanceState(fragment);
if (savedState != null) {
fragmentState.mSavedFragmentState = savedState.mState;
}
mFragmentStates.set(position, fragmentState);
mFragments.set(position, null);
}
mCurTransaction.remove(fragment);
}
#Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
Fragment fragment = (Fragment) object;
if (fragment != mCurrentPrimaryItem) {
if (mCurrentPrimaryItem != null) {
mCurrentPrimaryItem.setMenuVisibility(false);
mCurrentPrimaryItem.setUserVisibleHint(false);
}
if (fragment != null) {
fragment.setMenuVisibility(true);
fragment.setUserVisibleHint(true);
}
mCurrentPrimaryItem = fragment;
}
}
#Override
public void finishUpdate(ViewGroup container) {
if (mCurTransaction != null) {
mCurTransaction.commitAllowingStateLoss();
mCurTransaction = null;
mFragmentManager.executePendingTransactions();
// Fix: Fragment is added by transaction. BUT didn't add to FragmentManager's mActive.
for (Fragment fragment : mFragments) {
if (fragment != null) {
fixActiveFragment(mFragmentManager, fragment);
}
}
}
}
#Override
public boolean isViewFromObject(View view, Object object) {
return ((Fragment) object).getView() == view;
}
#Override
public Parcelable saveState() {
Bundle state = null;
// 目前顯示的 Fragments
for (int i = 0; i < mFragments.size(); i++) {
Fragment f = mFragments.get(i);
if (f != null && f.isAdded()) {
if (state == null) {
state = new Bundle();
}
String key = "f" + i;
mFragmentManager.putFragment(state, key, f);
}
}
if (mFragmentStates.size() > 0) {
if (state == null) {
state = new Bundle();
}
FragmentState[] fs = new FragmentState[mFragmentStates.size()];
mFragmentStates.toArray(fs);
state.putParcelableArray("states_fragment", fs);
}
return state;
}
#Override
public void restoreState(Parcelable state, ClassLoader loader) {
if (state != null) {
Bundle bundle = (Bundle) state;
bundle.setClassLoader(loader);
Parcelable[] fs = bundle.getParcelableArray("states_fragment");
mFragments.clear();
mFragmentStates.clear();
mFragmentTags.clear();
mFragmentClassNames.clear();
mFragmentArgs.clear();
if (fs != null) {
for (int i = 0; i < fs.length; i++) {
FragmentState fragmentState = (FragmentState) fs[i];
mFragmentStates.add(fragmentState);
if (fragmentState != null) {
mFragmentArgs.add(fragmentState.mArguments);
mFragmentTags.add(fragmentState.mTag);
mFragmentClassNames.add(fragmentState.mClassName);
} else {
mFragmentArgs.add(null);
mFragmentTags.add(null);
mFragmentClassNames.add(null);
}
mFragments.add(null);
}
}
Iterable<String> keys = bundle.keySet();
for (String key : keys) {
if (key.startsWith("f")) {
int index = Integer.parseInt(key.substring(1));
Fragment f = mFragmentManager.getFragment(bundle, key);
if (f != null) {
f.setMenuVisibility(false);
mFragments.set(index, f);
mFragmentArgs.set(index, f.mArguments);
mFragmentTags.set(index, f.mTag);
mFragmentClassNames.set(index, f.getClass().getName());
} else {
Log.w(TAG, "Bad fragment at key " + key);
}
}
}
// If restore will change
notifyDataSetChanged();
}
}
public static void fixActiveFragment(FragmentManager fragmentManager, Fragment fragment) {
FragmentManagerImpl fm = (FragmentManagerImpl) fragmentManager;
if (fm.mActive != null) {
int index = fragment.mIndex;
Fragment origin = fm.mActive.get(index);
if (origin != null) {
if ((origin.mIndex != fragment.mIndex) || !(origin.equals(fragment))) {
Log.e(TAG,
String.format("fixActiveFragment: Not Equal! Origin: %s %s, Fragment: %s $s",
origin.getClass().getName(), origin.mIndex,
fragment.getClass().getName(), fragment.mIndex
));
}
}
fm.mActive.set(index, fragment);
}
}
// Fix
// http://stackoverflow.com/questions/10396321/remove-fragment-page-from-viewpager-in-android
#Override
public int getItemPosition(Object object) {
int index = mFragments.indexOf(object);
if (index < 0) {
return PagerAdapter.POSITION_NONE;
}
boolean isPositionChange = mTempPositionChange[index];
int result = PagerAdapter.POSITION_UNCHANGED;
if (isPositionChange) {
result = PagerAdapter.POSITION_NONE;
}
return result;
}
}

2020 now.
Simple add this to PageAdapter:
override fun getItemPosition(`object`: Any): Int {
return PagerAdapter.POSITION_NONE
}

You could just override the destroyItem method
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
fragmentManager.beginTransaction().remove((Fragment) object).commitNowAllowingStateLoss();
}

I hope this can help what you want.
private class MyPagerAdapter extends FragmentStatePagerAdapter {
//... your existing code
#Override
public int getItemPosition(Object object){
return PagerAdapter.POSITION_UNCHANGED;
}
}