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i have a dynamic tablayout but every time i push back button and re-enter my app again , my tab doubles , why?

in my TabLayout i create my login TabItem dynamically at the onCreate() method of my MainActivity , but every time i exit from my application with back button and i re-enter my app , it creates that login TabItem again and so it doubles it every time , i tried to check and use :
if(savedInstanceState == null) {
// create the first tab
}
but it didn't work , can you please help me ?
here is my code for the MainActivity :
public class MainActivity extends AppCompatActivity {
TabLayout tabLayout;
ViewPager viewPager;
public static List<Fragment> fragments = new ArrayList<>();
public static List<String> fragmentsTitle = new ArrayList<>();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tabLayout = findViewById(R.id.myTabLayout);
viewPager = findViewById(R.id.myViewPager);
MyViewPagerAdapter Adapter = new MyViewPagerAdapter(getSupportFragmentManager());
Adapter.createTab(new LoginFragment(), "Login", getSupportFragmentManager(), viewPager);
viewPager.setAdapter(Adapter);
tabLayout.setupWithViewPager(viewPager);
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
public void onTabSelected(TabLayout.Tab tab) {
}
public void onTabUnselected(TabLayout.Tab tab) {
}
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
}
and this is the code for FragmentPagerAdapter
public class MyViewPagerAdapter extends FragmentPagerAdapter {
public MyViewPagerAdapter(FragmentManager manager) { super(manager);}
public void createTab(Fragment fragment, String title, FragmentManager manager, ViewPager viewPager) {
MyViewPagerAdapter Adapter = new MyViewPagerAdapter(manager);
MainActivity.fragments.add(fragment);
MainActivity.fragmentsTitle.add(title);
Adapter.notifyDataSetChanged();
viewPager.setAdapter(Adapter);
}
public Fragment getItem(int position) {
return MainActivity.fragments.get(position);
}
public CharSequence getPageTitle(int position) {
return MainActivity.fragmentsTitle.get(position);
}
public int getCount() {
return MainActivity.fragments.size();
}
}

Try removing static keyword from your list in MainActivity. Instead use final to prevent reinitialisation of list.
It's creating that tab everytime because static things stay alive as long as they get killed. And the professional way on earth to create tab and store them inside list is to keep that list inside viewpager adaptor.
I am happy it was helpful.

Tabs in Android disappears. Code was working before but now it stopped working

I have used Tab Control and RecyclerView together in Android. The way it functions is I have SearchBar in the toolbar. When the user enters the search query in the search bar. Upon hitting the search button, tab's Fragments are supposed to be loaded with data. Issues are as follows.
1) Tabs icon disappear
2) When debugging through the code found (Since I am using ViewPager with Tab Layout to implement Tabs in android) that getItem method of PagerAdapter class is called twice every time getItem is triggered.
I am stuck and don't know what to do. Not much help online as well.
1) Tab initialization Code:-
private TabLayout tabLayout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tabLayout = (TabLayout)findViewById(R.id.tablayout);
tabLayout.addTab(tabLayout.newTab().setIcon(R.mipmap.craigslist_new1));
tabLayout.addTab(tabLayout.newTab().setIcon(R.mipmap.kijiji_new1));
tabLayout.addTab(tabLayout.newTab().setIcon(R.mipmap.letgo_new1));
tabLayout.addTab(tabLayout.newTab().setIcon(R.mipmap.varagesale_new1));
tabLayout.addTab(tabLayout.newTab().setIcon(R.mipmap.facebook_new1));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
drawerLayout = findViewById(R.id.drawer_layout);
}
#Override
public boolean onQueryTextSubmit(String query) {
//loadRecyclerViewData(query);
Bundle bundle = new Bundle();
bundle.putString("searchText", query);
final ViewPager viewPager = (ViewPager)findViewById(R.id.pager);
final PageAdapter adapter = new PageAdapter(getSupportFragmentManager(), tabLayout.getTabCount(), bundle);
viewPager.setAdapter(adapter);
viewPager.setOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setupWithViewPager(viewPager);
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return true;
}
2) PagerAdapter:-
public class PageAdapter extends FragmentStatePagerAdapter {
int mNoofTabs;
Bundle bundle;
public PageAdapter(FragmentManager fragmentManager, int NumberOfTabs, Bundle bundle)
{
super(fragmentManager);
this.mNoofTabs = NumberOfTabs;
this.bundle = bundle;
}
#Override
public Fragment getItem(int i) {
switch(i)
{
case 0 :
CraigslistFragment tab1 = new CraigslistFragment();
tab1.setArguments(bundle);
return tab1;
case 1:
KijijiFragment tab2 = new KijijiFragment();
tab2.setArguments(bundle);
return tab2;
case 2:
letgoFragment tab3 = new letgoFragment();
tab3.setArguments(bundle);
return tab3;
case 3:
VaragesaleFragment tab4 = new VaragesaleFragment();
tab4.setArguments(bundle);
return tab4;
case 4:
FacebookFragment tab5 = new FacebookFragment();
tab5.setArguments(bundle);
return tab5;
default:
return null;
}
}
#Override
public int getCount() {
return mNoofTabs;
}
}

load fragment in ViewPager only when its selected

I have a ViewPager with 3 tabs.
I'm loading big data in every fragments.
The app load every fragments but I want to load fragment only when its selected.
How can I do that? I have no idea.
I'm waiting for your help. Thank you
my code:
public class Fragments extends AppCompatActivity {
private TabLayout tabLayout;
private ViewPager viewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_tabs);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new FirstFragment(), "1");
adapter.addFragment(new SecondFragment(), "2");
adapter.addFragment(new ThirdFragment(), "3");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
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();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}

If no one has given you a good answer I know this is 5 years later, but anyone reading this. I'm actually having the opposite problem. I need to load all tabs at the same time. What is happening to me now is only one tab is loading at a time. I need to use this adapter for viewpager2 with tablayout so that I can disable the viewpager swiping left to right for my specific usecase.
Here is my code:
WARNING CODE IS IN KOTLIN NOT JAVA
class RecipeTabAdapter internal constructor(fm: FragmentManager, lifecycle: Lifecycle) : FragmentStateAdapter(fm, lifecycle) {
val fragmentsList: ArrayList<Fragment> = arrayListOf()
fun addFragment(fragment: Fragment) {
fragmentsList.add(fragment)
}
override fun getItemCount(): Int {
return fragmentsList.size
}
override fun createFragment(position: Int): Fragment {
when (position) {
position -> fragmentsList[position]
position -> fragmentsList[position]
}
return fragmentsList[position]
}
}

Is it possible to disable the offscreen page limit?
No. It is already set to the minimum possible value: one page to each side of the viewed page. This is necessary to have the animation effects work -- you see parts of two fragments (original and new) at the same time.

In
OncreateView(){
//.... dont initialize your view here
if(isMenuVisible()) { // menu should be visible if current fragment is visible right now
setUserVisibleHint(true); // manually set value to true
}
}
in
oncreate(){
setHasOptionsMenu(true);
}
Finally there is method called setuservisiblehint() which is only called when the fragment is visible to the user this is the only method where you shud initialize all your views.
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if(isVisibleToUser && v != null) {
// initialize your view here and call you fetch_data_function()
}

Here's my solution and it works as expected. In all of your child fragments create a boolean variable:
private boolean loadFragmentExecuted = false;
in the child fragments create a generic method called loadFragment and move all of the logic you added in onCreateView to that method:
public void loadFragment()
{
if(!loadFragmentExecuted)
{
//Add your logic to manipulate the UI or load data etc...
loadFragmentExecuted = true;
}
}
in your pageview logic create the fragments dynamically like:
//add the fragment
String fragmentName = "com.something." + fragmentId;
//check if the class exists
try
{
Class myFragmentClass = Class.forName(fragmentName);
Fragment myFragment = (Fragment) myFragmentClass.newInstance();
mFragments.add(myFragment);
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
}
catch (IllegalAccessException e)
{
e.printStackTrace();
}
catch (InstantiationException e)
{
e.printStackTrace();
}
then set your pager adapter and attach a tablayout with it:
//set our pager adapter that contains different fragments
mPagerAdapter = new BasePagerAdapter(mFragmentManager, mFragments);
//link the adapter to the viewpager
mViewPager.setAdapter(mPagerAdapter);
//cache fragments
int limit = (mPagerAdapter.getCount() > 0 ? mPagerAdapter.getCount() : 1);
mViewPager.setOffscreenPageLimit(limit);
//add the page listner to the viewPager and link it to the tabLayout
mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(mTabLayout));
//on tab selected select current viewpager item
mTabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener()
{
#Override
public void onTabSelected(TabLayout.Tab tab)
{
mViewPager.setCurrentItem(tab.getPosition());
//get fragment for the selected tab
Fragment f = mPagerAdapter.getItem(tab.getPosition());
//load the content of the fragment
try
{
Class c = f.getClass();
Method loadFragment = c.getMethod("loadFragment");
loadFragment.invoke(f);
}
catch (IllegalAccessException e){}
catch (InvocationTargetException e){}
catch (NoSuchMethodException e){}
}
#Override
public void onTabUnselected(TabLayout.Tab tab)
{
}
#Override
public void onTabReselected(TabLayout.Tab tab)
{
}
});

I have a solution that does not require subclassing, and it's easy to introduce into existing projects. It uses the child fragment mechanism.
The basic idea is to replace your content fragment with an almost empty fragment, and add your content fragment as a child fragment when it is really visible to the user
The gist of the code is like this
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
boolean hasFragment = getChildFragmentManager().findFragmentById(R.id.container) != null;
if (hasFragment) {
return;
}
if (getUserVisibleHint()) {
addFragment("onViewCreated");
}
}
#Override
public void onResume() {
super.onResume();
if (getUserVisibleHint()) {
addFragment("onResume");
}
}
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser && isResumed()) {
addFragment("setUserVisibleHint");
}
}
private void addFragment(String cause) {
if (getChildFragmentManager().findFragmentById(R.id.container) == null) {
getChildFragmentManager().beginTransaction()
.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out)
.add(R.id.container, createFragment()).commit();
}
}
Check out my full solution here, which also contains a progressbar, and the option to automatically start loading of background fragments with a specified delay: Lazy Load Fragment

Updating the contents on tab changed in view pager

I am scracthing my head for past 1 day but unable to find the solution.
In mine application there are two tabs under the toolbar
First tab is USER-TAB
the second one is ADMIN-TAB
In both the tabs there are the listView. When a ListItem on the USER-TAB is clicked a dialog appears and user take some action.
Now after this when the ADMIN-TAB is Selected the Admin should get refreshed with new sets of data. But It's not. On selecting the ADMIN-TAB the onResume() method and everyting is getting called but it is not able to update the list.
I wont be able to write the Whole code, I am giving some snippet.
Basically I have taken the code from this link
https://github.com/codepath/android_guides/wiki/Sliding-Tabs-with-PagerSlidingTabStrip
In My Main Activity I have written the OpPageChangeListener.
public class MaterialTab extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.material_main_sample);
// Get the ViewPager and set it's PagerAdapter so that it can display items
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
viewPager.setAdapter(new SampleFragmentPagerAdapter(getSupportFragmentManager()));
// Give the PagerSlidingTabStrip the ViewPager
PagerSlidingTabStrip tabsStrip = (PagerSlidingTabStrip) findViewById(R.id.tabs);
// Attach the view pager to the tab strip
tabsStrip.setViewPager(viewPager);
tabsStrip.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
if(position == 0){
MileUserFragment userFragment = new MileUserFragment();
final FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.detach(userFragment);
ft.attach(userFragment);
ft.commit();
} if(position == 1){
MileAdminFragment adminFragment = new MileAdminFragment();
final FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.detach(adminFragment);
ft.attach(adminFragment);
ft.commit();
}
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
}
}
OnPageSelected You can see I am detaching and reattaching the fragment.Everything is working fine. Both Fragments OnResume() are getting called but the List is not getting changed. I don't undrstand why
For additional assistance i am adding snippet one Fragment. Hope this will give some Idea where i might be going wrong
public class MileUserFragment extends Fragment {
#Override
public void onResume() {
super.onResume();
new GetAdminDbTask().execute();
if(!internetUtil.isConnectedToInternet(getActivity())){
mSwipeRefreshLayout.setRefreshing(false);
mSwipeRefreshLayout.setEnabled(false);
}
}
public class GetAdminDbTask extends AsyncTask<Admin, Void, String> {
#Override
protected String doInBackground(Admin... parmas) {
_adminList = shipmentDbHandler.getAllAdmin();
return "";
}
#Override
protected void onPostExecute(String str) {
mAdminAdapter = new AdminAdapter(getActivity(), _adminList);
adminListView.setAdapter(mAdminAdapter);
mAdminAdapter.notifyDataSetChanged();
// Set the refresh Listener to false after the list has been loaded with new set of data
if (mSwipeRefreshLayout.isRefreshing()) {
mSwipeRefreshLayout.setRefreshing(false);
}
if(_adminList.size() > 0 ){
mAdminAdapter = new AdminAdapter(getActivity(), _adminList);
adminListView.setAdapter(mAdminAdapter);
mAdminAdapter.notifyDataSetChanged();
}
}
}
}
public class SampleFragmentPagerAdapter extends FragmentPagerAdapter {
final int PAGE_COUNT = 2;
private String tabTitles[] = new String[] { "Tab1", "Tab2" };
private FragmentManager fragmentManager;
public SampleFragmentPagerAdapter(FragmentManager fm) {
super(fm);
this.fragmentManager = fm;
}
#Override
public int getCount() {
return PAGE_COUNT;
}
#Override
public Fragment getItem(int position) {
FragmentTransaction ft = null;
if(position == 0){
MileUserFragment userFragment = new MileUserFragment();
return userFragment;
}
if(position == 1){
MileAdminFragment adminFragment = new MileAdminFragment();
return archiveFragment;
}
}
#Override
public CharSequence getPageTitle(int position) {
// Generate title based on item position
return tabTitles[position];
}
}

Haah.. Finally i got an answer to after an heck of losing almost 1 and half days. It might be not completely good answer but atleast it is one of the closest I got.
First of all MainActivity.java looks like:
tabs.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
int scrollPosition = 0;
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
if(position == 0){
scrollPosition = 0;
}
if(position == 1){
scrollPosition = 1;
}
}
#Override
public void onPageSelected(int position) {
}
#Override
public void onPageScrollStateChanged(int state) {
if(state == pager.SCROLL_STATE_IDLE){
if(scrollPosition == 0 && application.isActiveAction()){
viewPagerAdapter.notifyDataSetChanged();
application.setActiveAction(false);
}
if(scrollPosition == 1 && application.isArchiveAction()){
viewPagerAdapter.notifyDataSetChanged();
application.setArchiveAction(false);
}
}
}
});
Now what I have done here is I have set OnPageChangeListener and in this I am keeping track of the position whenever the tabs are changing. For my needs what i have done is i have created two boolean variables and setting it when any content on those tab are changing in Application scope. Now when the contents on one tab has been changed or some Action are done I am calling
viewPagerAdapter.notifyDataSetChanged() // Now this is the real gem
after invoking this it will make a call to the ViewPagerAdapter function
#Override
public int getItemPosition(Object object) {
return PagerAdapter.POSITION_NONE; // This will get invoke as soon as you call notifyDataSetChanged on viewPagerAdapter.
}
Also the Point is your ViewPagerAdapter should extend FragmentStatePageAdapter. Now the Point is
PagerAdapter.POSITION_NONE
will not cache the fragment and reload a new fragment for that tab position.
Basic idea is we should not make or retutn PagerAdapter.POSITION_NONE everytime on sliding of tab since it destroys the cached element and reload the fragment which affects UI performance.
So finally the basic thing is always check that whether on calling viewPagerAdapter.notifyDataSetChanged() the function getItemPosition() should also gets invoked. Hope it will help somebody. For better perfomance you can make changes according to your requirement.
I got the needed breakthrough and understanding from this post : #Louth Answer
Remove Fragment Page from ViewPager in Android

Just put
viewPager.setCurrentItem(tab.getPosition());
in your onTabSelected method like:
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});

Android: Activity losing link to ViewPager Fragment

I am having trouble with an Activity that fires off a command to a fragment in a ViewPager using a FragmentNotification interface. Everything works well until either the app is in the background for a long period of time or the orientation changes. At that point the Activity seems to lose connection to the Fragment.
My Activity code:
public class MyActivity extends FragmentActivity implements MyFragment3.FragmentNotification {
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
MyFragment1 fragOne = new MyFragment1();
MyFragment2 fragTwo = new MyFragment2();
MyFragment3 fragThree = new MyFragment3();
boolean toggle = false;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setOffscreenPageLimit(2);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.setClickable(true);
mViewPager.setCurrentItem(0);
}
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
if (fragThree != null) {
fragThree.doSomething();
toggle = false;
return false;
} else {
}
}
return super.onKeyDown(keyCode, event);
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int i) {
Fragment fragment;
if(i==0){
fragment = fragOne;
}else if(i==1){
fragment = fragTwo;
}else{
fragment = fragThree;
}
return fragment;
}
#Override
public int getCount() {
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0: return getString(R.string.title_section1).toUpperCase();
case 1: return getString(R.string.title_section2).toUpperCase();
case 2: return getString(R.string.title_section3).toUpperCase();
}
return null;
}
}
//Receive an event notification from a fragment
// #Override
public void fragmentAction(int actionType) {
if (actionType == MyFragment3.TOGGLE_ACT) {
toggle = true;
}
}
}
My Fragment Code:
public class MyFragment3 extends Fragment {
View mView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
...
mView = ....
return rootView;
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mListener = (FragmentNotification) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement OnArticleSelectedListener");
}
}
public void doSomething(){
mView.setVisibility(View.GONE);
...
}
public interface FragmentNotification {
public void fragmentAction(int actionType);
}
}
As mentioned, everything works well until some state change, and then it appears the activity loses reference to the fragment present in the viewpager, even though it is being displayed properly until the back button is pressed.
I believe I need to restore the connection by supplying a bundle from my Fragment's onSaveInstanceState, but have no idea how to get started.
Any help would be greatly appreciated.
Thanks,
Josh

You are blindly creating instances of your three fragments, in data member initializers (!), even if those fragments already exist. Bear in mind that Android recreates all of your existing fragments on a configuration change. Hence, on a configuration change, none of those newly-created fragments will get used, as the ViewPager will use the ones Android recreated for it. You can see this in the implementation of instantiateItem() in FragmentPagerAdapter (source code is in your SDK).
The concept that "when pressing BACK I want to do something special with my third fragment in the pager" is not something that ViewPager supports all that well. I would encourage you to find some other solution to whatever problem you are trying to solve with that logic.