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how to fix" 3 fragment in One activity with viewPager need validation first two page then possible to go third page"

I want to create a createOrderActivity where has three fragments like Service info, ScheduleInfo, confirmation
the service info fragment has editText
if click NextButton(which is situated CreateOrderActivity) check validation editText first. then move ScheduleFragment page.
if first two pages validation ok then move to Confirmation Fragment page.
Here is the FragmentViewpagerAdapter class
public class FragmentViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> fragmentList = new ArrayList<>();
private final List<String> fragmentTitleList = new ArrayList<>();
public FragmentViewPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return fragmentList.get(position);
}
#Override
public int getCount() {
return fragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
fragmentList.add(fragment);
fragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return fragmentTitleList.get(position);
}
}
In CreateOrderActivity class
#Override
public void onPageSelected(int position) {
boolean checkSch= false;
if (position == 1) {
ServiceInfoFragment serviceInfoFragment = new ServiceInfoFragment();
//checking validation from ServiceInfoFragment fragment Class
if (serviceInfoFragment.checkServiceValidation()) {
checkSch = true;
//Toast.makeText(CreateOrderActivity.this, "Validation okay", Toast.LENGTH_SHORT).show();
}else {
checkSch = false;
// Toast.makeText(CreateOrderActivity.this, "Please check validation", Toast.LENGTH_SHORT).show();
pagerCreateOrder.setCurrentItem(position-1);
}
}
if (position == 2) {
if (checkSch){
ScheduleFragment scheduleFragment = new ScheduleFragment();
if (scheduleFragment.checkScheduleValidation()) {
Toast.makeText(CreateOrderActivity.this, "Validation okay", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(CreateOrderActivity.this, "Please check S validation", Toast.LENGTH_SHORT).show();
pagerCreateOrder.setCurrentItem(position-1);
}
}else {
Toast.makeText(CreateOrderActivity.this, "Please check validation", Toast.LENGTH_SHORT).show();
pagerCreateOrder.setCurrentItem(position-2);
}
}
}
//checking checkScheduleValidation() in ScheduleFragment class. return null exception
*bellow mehtod declear in Fragment *
public boolean checkServiceValidation(){
return true;
}
I upload this Image
I used this Reference

I found a solution in my way. I have loaded three fragments in a viewpager. In the second fragment, there is one edittext. on clicking the next button, there is a validation for checking email. On the basis of validation next fragment is loaded. All the Fragments are loaded as singleton . You might have caused null pointer exception , because of multiple instance of fragments.
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private SectionsPagerAdapter mSectionsPagerAdapter;
private FragmentTwo fragmentTwo;
private ViewPager mViewPager;
Button back, next;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
back = findViewById(R.id.back);
next = findViewById(R.id.next);
next.setOnClickListener(this);
back.setOnClickListener(this);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.vp_viewpager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int i, float v, int i1) {
}
#Override
public void onPageSelected(int i) {
if (i==2){
if (!fragmentTwo.checkEditText()) {
Toast.makeText(getApplicationContext(),"False",Toast.LENGTH_LONG).show();
mViewPager.setCurrentItem(i-1);
return;
}
}
}
#Override
public void onPageScrollStateChanged(int i) {
}
});
}
private void changeViewPagerPosition(int position) {
int totalCount = mViewPager.getAdapter().getCount();
if (position < 0 || position >= totalCount) {
return;
}
mViewPager.setCurrentItem(position);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public void onClick(View view) {
int currentViewpagerPosition = mViewPager.getCurrentItem();
switch (view.getId()) {
case R.id.back:
changeViewPagerPosition(currentViewpagerPosition - 1);
break;
case R.id.next:
if (currentViewpagerPosition==1){
if (!fragmentTwo.checkEditText()) {
Toast.makeText(getApplicationContext(),"Falsee",Toast.LENGTH_LONG).show();
return;
}
}
changeViewPagerPosition(currentViewpagerPosition + 1);
break;
}
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return FragmentOne.newInstance(position);
case 1:
return fragmentTwo=FragmentTwo.getInstance();
case 2:
return FragmentThree.newInstance(position);
default:
return FragmentThree.newInstance(position);
}
}
#Override
public int getCount() {
return 3;
}
}
}
The Fragment 2
public class FragmentTwo extends Fragment {
EditText email;
private static FragmentTwo fragment=null;
public FragmentTwo() {
}
public static FragmentTwo getInstance() {
if (fragment == null){
fragment = new FragmentTwo();
}
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_two, container, false);
return rootView;
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
email = getView().findViewById(R.id.editText);
}
public boolean emailValidator()
{
Pattern pattern;
Matcher matcher;
final String EMAIL_PATTERN = "^[_A-Za-z0-" +
"9-]+(\\.[_A-Za-z0-9-]+)*#[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
pattern = Pattern.compile(EMAIL_PATTERN);
matcher = pattern.matcher(email.getText().toString());
return matcher.matches();
}
public Boolean checkEditText(){
if (emailValidator()){
return true;
}
return false;
}
}

Unable to Delete a fragment from ViewPager

My goal is to delete a fragment from a ViewPager upon user button click.
Populating the ViewPager works fine, but when I try to delete it, I get an error indicating a null reference. I incorporated Remove Fragment Page from ViewPager in Android
In my fragment to be deleted I have:
Button delete = (Button) getActivity().findViewById(R.id.dont_show_button_1);
delete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
db.deletePerson(count); // SQLiteDatabase, works fine
displayActivity.removeCurrentFragment(count-1);
}
});
DisplayActivity is as follows:
public class DisplayActivity extends FragmentActivity {
ViewPager viewPager;
PagerAdapter pagerAdapter;
String TAG = "DisplayActivity";
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.db_layout);
viewPager = (ViewPager) findViewById(R.id.pager);
pagerAdapter = new PagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(pagerAdapter);
}
public void removeCurrentFragment(int position){
pagerAdapter.fragmentArrayList.remove(position);
pagerAdapter.notifyChangeInPosition(1);
pagerAdapter.notifyDataSetChanged();
Log.e(TAG, "in removeCurrentFragment");
}
}
PagerAdapter
public class PagerAdapter extends FragmentPagerAdapter {
long baseId = 0;
public static List<Fragment> fragmentArrayList = new ArrayList<Fragment>();
public PagerAdapter(FragmentManager fm){
super(fm);
fragmentArrayList.add(new FragmentOne());
fragmentArrayList.add(new FragmentTwo());
fragmentArrayList.add(new FragmentThree());
}
#Override
public Fragment getItem(int position) {
return fragmentArrayList.get(position);
}
#Override
public int getCount() {
return fragmentArrayList.size();
}
#Override
public int getItemPosition(Object object){
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;
}
}
This is the error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void .DisplayActivity.removeCurrentFragment(int)' on a null object reference
Triggered from the fragment
Edit:
public class FragmentOne extends Fragment {
DatabaseHelper db;
WebView mWebView;
DisplayActivity displayActivity;
int count = 1;
This is how I get reference from displayActivity, is this the wrong way to get a reference of it?

if (count > 0) {
displayActivity.removeCurrentFragment(count - 1);
}

Android Fragments Not Updating

I am trying to create a very simple Android application that uses a FragmentPagerAdapter to swipe between three fragments. Each of the fragments contains a single EditText and has the exact same code.
The desired behavior is that when the user updates the EditText, the new value is saved to the application instance. Then, once a new fragment is selected, that new fragment should show the saved value. For some reason this is not working.
I also want the focused fragment to show the saved data when the application resumes (comes back from background). This too does not work.
I am really confused as to why something as simple as this is so difficult!
Here is my code so far:
StackOverflowDemoApplication.java:
public class StackOverflowDemoApplication extends Application {
private ApplicationData applicationData;
// the index of the last fragment that was displayed
private int lastItem = 0;
#Override
public void onCreate() {
applicationData = new ApplicationData();
}
public ApplicationData getApplicationData() {
return applicationData;
}
public int getLastItem() {
return lastItem;
}
public void setLastItem(int lastItem) {
this.lastItem = lastItem;
}
}
MainActivity.java
public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {
private static final String TAG = "MainActivity";
// the application instance
private StackOverflowDemoApplication application;
// the pager adapter
private SectionsPagerAdapter pagerAdapter;
// the view pager
private ViewPager viewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Save the application instance.
application = (StackOverflowDemoApplication) getApplication();
// Set up the action bar.
final ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
pagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(pagerAdapter);
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < pagerAdapter.getCount(); i++) {
actionBar.addTab(
actionBar.newTab()
.setText(pagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
#Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
viewPager.setCurrentItem(tab.getPosition());
pagerAdapter.notifyDataSetChanged();
}
#Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
#Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
private int NUM_ITEMS = 3;
public SectionsPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
#Override
public Fragment getItem(int position) {
// get the application data instance
ApplicationData data = application.getApplicationData();
switch (position) {
case 0:
return SecondFragment.newInstance(data);
case 1:
return FirstFragment.newInstance(data);
case 2:
return ThirdFragment.newInstance(data);
default:
return null;
}
}
#Override
public int getCount() {
return NUM_ITEMS;
}
public int getItemPosition(Object object) {
return POSITION_NONE;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "FIRST FRAGMENT";
case 1:
return "SECOND FRAGMENT";
case 2:
return "THIRD FRAGMENT";
default:
return null;
}
}
}
#Override
public void onResume() {
// load the previous fragment
viewPager.setCurrentItem(application.getLastItem());
super.onResume();
}
#Override
public void onPause() {
// save the last fragment we used
application.setLastItem(viewPager.getCurrentItem());
super.onPause();
}
}
FirstFragment.java
public class FirstFragment extends Fragment {
private static final String TAG = "FirstFragment";
// the activity reference
private Activity activity;
// the application data
private ApplicationData data;
// the edit text
private EditText editText;
// are we currently loading data for this fragment?
private boolean loadingData = false;
public FirstFragment(ApplicationData data) {
super();
this.data = data;
}
public static FirstFragment newInstance(ApplicationData data) {
Log.e(TAG, "New instance called");
FirstFragment fragment = new FirstFragment(data);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.e(TAG, "Creating FirstFragment view");
// inflate the view
View view = inflater.inflate(R.layout.first_fragment_layout, container, false);
// get the activity instance
activity = getActivity();
// the textview
editText = (EditText) view.findViewById(R.id.textView);
editText.addTextChangedListener(textWatcher);
// update the ui from the data
updateUIFromData();
return view;
}
public void updateUIFromData() {
// we have started loading the data
loadingData = true;
// if there is data
if (null != data) {
// set the value
if (null != data.getStringValue()) {
editText.setText(data.getStringValue());
}
}
// done loading the data
loadingData = false;
}
private void updateDataFromUi() {
data.setStringValue(editText.getText().toString());
}
private TextWatcher textWatcher = new TextWatcher() {
#Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
#Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// if we are not loading data
if (!loadingData) {
// update the data from the ui
updateDataFromUi();
}
}
#Override
public void afterTextChanged(Editable s) {
}
};
}

Try to update view when fragment get visible to user as follows:
public class MyFragment extends Fragment
#Override
public void setMenuVisibility(final boolean visible) {
super.setMenuVisibility(visible);
if (visible) {
**//Get new data and update views here**
}
}

Check this tutorial, it might help you:
http://www.androidhive.info/2013/10/android-tab-layout-with-swipeable-views-1/
You don't have to call notifyDataSetChanged() inside tabSelected callback.

You should update your fragment datas in onResumer() like TextView or EditText ... etc. See example:
Oncreate....
TextView mtextview = rootview.findViewById....
#Override
public void onResume() {
if(do some thing){
mtextview.setText("It did something");
}
super.onResume();
}

How to save state of Fragments in ViewPager when orientation changes

I have an application that Implements ActionBarSherlock, it's mainly composed of
ViewPager with different content of fragments (for each page), with ViewPager indicator.
Here is my onCreate Method of the Activity that extends SherlockFragmentActivity
// Assume that tabs,sources,types are string arrays e.g. tabs = ["tab1","tab2","tab3"]
// types = ["listview","listview","webview"]
// according to the type of each tab, the type of content of the fragment associated to that tab is determined (e.g. WebView or ListView)
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
super.setContentView(R.layout.main);
srcContext = getBaseContext();
srcActivity = SaudiActivity.this;
int selectPos = 0;
Intent sender = getIntent();
FragmentPagerAdapter mAdapter = new NewsListAdapter(
getSupportFragmentManager());
ViewPager pager = (ViewPager) findViewById(R.id.pager);
pager.setAdapter(mAdapter);
TabPageIndicator indicator = (TabPageIndicator) findViewById(R.id.indicator);
indicator.setViewPager(pager);
pager.setOffscreenPageLimit(tabs.length);
pager.setCurrentItem((tabs.length - 1));
currentPosition = (tabs.length - 1);
indicator.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
currentPosition = position;
if ((type[position] == "listview" || type[position]
.equals("listview")) && loaded[position] == false) {
loaded[position] = true;
getNews(listViews[position], position);
}
}
#Override
public void onPageScrolled(int position, float positionOffset,
int positionOffsetPixels) {
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
getSupportActionBar().setCustomView(R.layout.logo);
getSupportActionBar().setDisplayShowCustomEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(false);
getSupportActionBar().setDisplayShowTitleEnabled(false);
getSupportActionBar().setDisplayShowHomeEnabled(false);
Context ctx = getSupportActionBar().getThemedContext();
SourcesAdapter adapter = new SourcesAdapter(ctx,
R.layout.navigation_list_item, src_name, icons, src_value);
}
Here are my News List Adapter (that creates the fragments),
public static class MyViewHolder {
public TextView title;
public ImageView icon;
}
class NewsListAdapter extends FragmentPagerAdapter {
public NewsListAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return new NewsFragment(MyActivity.this, position);
}
// This is the number of pages -- 5
#Override
public int getCount() {
return tabs.length;
}
// This is the title of the page that will apppear on the "tab"
public CharSequence getPageTitle(int position) {
return tabs[position];
}
}
public List<NewsItem> NewsItems;
Finally here's my NewsFragment:
public static class NewsFragment extends Fragment {
private int position;
public NewsFragment() {
}
public NewsFragment(Context ctx, int pos) {
this.position = pos;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = null;
if (type[position].equals("listview")) {
// Put a ListView in the Fragment
} else {
// Put a WebView in the Fragment
}
return view;
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
}

Let the fragment handle it's state by overriding onSaveInstanceState and placing the necessary values into outState. Recover that state in onCreateView using savedInstanceState. Also I'm pretty sure that if you're using Actionbarsherlock fragments need to extend SherlockFragment rather than Fragment.

How to Remove Fragment from FragmentPagerAdapter?

I know there are some topics about this here already but I could not find a solution which I could get to work for my case.
I have a working sliding gallery using a custom FragmentActivity and FragmentPagerAdapter which holds a list of Fragments.
Within the FragmentActivity is a ImageView "delete". If clicked, the function deleteMedia() is called which then should remove the current Fragment and the following Fragment should be displayed.
How would I have to do that in my example?
FragmentActivity:
public class GalleryPagerActivity extends FragmentActivity implements OnClickListener {
private Intent intent;
private SharedPreferences settings;
private PagerAdapter mPagerAdapter;
private ViewPager mPager;
private List<Fragment> fragments;
private List<WhiteboardMedia> wiList;
private int selectedPosition;
private LinearLayout llTop;
private TextView tvTop;
private ImageView delete;
private ImageView share;
private TextView tvCounter;
private TextView tvFilename;
private TextView tvFilesize;
private TextView tvDate;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try {
super.setContentView(R.layout.gallery_pager);
intent = getIntent();
Type collectionType = new TypeToken<List<WhiteboardMedia>>(){}.getType();
wiList = gson.fromJson(intent.getStringExtra("wiList"), collectionType);
selectedPosition = intent.getIntExtra("position", 1);
llTop = (LinearLayout) findViewById(R.id.llTop);
llTop.setOnClickListener(this);
tvTop = (TextView) findViewById(R.id.tvTop);
tvTop.setOnClickListener(this);
delete = (ImageView) findViewById(R.id.imgDelete);
delete.setOnClickListener(this);
share = (ImageView) findViewById(R.id.imgShare);
share.setOnClickListener(this);
tvCounter = (TextView) findViewById(R.id.tvCounter);
tvFilename = (TextView) findViewById(R.id.tvFilename);
tvFilesize = (TextView) findViewById(R.id.tvFilesize);
tvDate = (TextView) findViewById(R.id.tvDate);
createContextMenu();
initDropbox();
} catch (Exception e) {
Log.e("GalleryPagerActivity", e.getLocalizedMessage());
}
}
/**
* Initialise the pager
*/
private void initialisePager() {
mPager = (ViewPager) super.findViewById(R.id.viewpager);
mPager.setAdapter(this.mPagerAdapter);
mPager.setOnPageChangeListener(new GalleryPageListener(tvCounter, tvFilename, tvFilesize, tvDate, wiList));
mPager.setCurrentItem(selectedPosition, true);
updatePage(selectedPosition);
}
public void updatePage(int position)
{
int focusedPage = position + 1;
Log.i("onPageSelected", "page selected " + position);
WhiteboardMedia wiImage = wiList.get(position);
String imageDate = "N/A";
try {
Date dateTaken= new Date(); //wiImage.getDate();
SimpleDateFormat sdf = new SimpleDateFormat("yy/MM/dd");
imageDate = sdf.format(dateTaken);
} catch (Exception e) {
}
try {
tvCounter.setText(focusedPage + "/" + wiList.size());
tvFilename.setText(wiImage.getFilename());
tvFilesize.setText(wiImage.getSize() + "a");
tvDate.setText(imageDate);
} catch (Exception e) {
}
}
#Override
protected void onResume() {
super.onResume();
}
#Override
public void onDestroy() {
super.onDestroy();
}
private WhiteboardMedia getActiveWhiteboardImage() {
return wiList.get(mPager.getCurrentItem());
}
private final int DELETE = 1;
#Override
public boolean onCreateOptionsMenu(Menu menu) {
menu.add(1, DELETE, 2, R.string.delete).setIcon(R.drawable.menu_btn_trash);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case DELETE:
deleteMedia();
return true;
}
return super.onContextItemSelected(item);
}
#Override
public void onClick(View v) {
if (v == delete) {
deleteMedia();
}
}
private void deleteMedia() {
// TODO delete the active Fragment and display the next Fragment in the list
}
/******************************************************************************
* Context Menu
*****************************************************************************/
private void createContextMenu() {
// context menu stuff
}
#Override
protected Dialog onCreateDialog(int id) {
// stuff
}
}
FragmentPagerAdapter:
public class GalleryPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> fragments;
public GalleryPagerAdapter(FragmentManager fm, List<Fragment> fragments) {
super(fm);
this.fragments = fragments;
}
#Override
public Fragment getItem(int position) {
return this.fragments.get(position);
}
#Override
public int getCount() {
return this.fragments.size();
}
}
Thanks for help!

that is the solution I'm using:
mViewPager : is the view you are using to set you Fragment
mViewPager = (YourViewPager) findViewById(R.id.myPager);
TABLE : is just a Integer list of the position of all my Fragments
public void destroyAllItem() {
int mPosition = mViewPager.getCurrentItem();
int mPositionMax = mViewPager.getCurrentItem()+1;
if (TABLE.size() > 0 && mPosition < TABLE.size()) {
if (mPosition > 0) {
mPosition--;
}
for (int i = mPosition; i < mPositionMax; i++) {
try {
Object objectobject = this.instantiateItem(mViewPager, TABLE.get(i).intValue());
if (objectobject != null)
destroyItem(mViewPager, TABLE.get(i).intValue(), objectobject);
} catch (Exception e) {
Log.i(TAG, "no more Fragment in FragmentPagerAdapter");
}
}
}
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
if (position <= getCount()) {
FragmentManager manager = ((Fragment) object).getFragmentManager();
FragmentTransaction trans = manager.beginTransaction();
trans.remove((Fragment) object);
trans.commit();
}
}

First, I suggest that you consider altering your FragmentPagerAdapter, to look more like the sample. You normally do not hold a list of fragments, any more than an ArrayAdapter normally holds a list of Views for the rows. Normally, you create the fragments on demand, and somebody else holds the list.
Then, to delete something, delete it from your model data (what the FragmentPagerAdapter normally wraps). Make sure that getCount() will then return the right number of items. Then, call notifyDataSetChanged() on the FragmentPagerAdapter, which should trigger a redraw of the ViewPager.

I found a solution ovverriding the method "onPostResume()" of the activity and calling the notifyDataSetChanged inside that.
#Override
protected void onPostResume() {
super.onPostResume();
if(this.mCustomPagerAdapter!=null){
this.mCustomPagerAdapter.notifyDataSetChanged();
}
}

If you are using FragmentPagerAdapter for adding and removing fragments at random position(not always at the end) dynamically, there is a method you need to taken more attention which is getItemId. By default, FragmentPagerAdapter uses position combines viewId as the tag name for fragments, however the position changes if you add or remove fragments. As a result, you may get an empty page because the position you are adding is occupied by an existing fragment. To solved this problem, override getItemId.
#Override
public long getItemId(int position) {
long itemId = ...; //Provide your unique ID here according to you logic
return itemId;
}

In my case, when i try to remove one item from the adapter, i will do as follow:
// get the position of item to remove
int position = getBinding().vp.getCurrentItem();
// remove the item from adapter
adapter.removeItem(position);
adapter.notifyDataSetChanged();
// minus one from the count
totalInvoice--;
updateTitle(getBinding().vp.getCurrentItem());
if (totalInvoice == 0) {
finish();
}
// set the adapter to view pager again
getBinding().vp.setAdapter(adapter);
// smooth scroll to given position
getBinding().vp.setCurrentItem(position);
The reason that i did above is that i find that even though you removed one from the data list, but the view of fragment still exist. So you have to let the view pager instantiate the view of given position. The answer above which trying to remove all fragments doesn't work for me. So, I find out the poor way of setting adapter to view pager again.