Develop Reference

Error when trying to set a TAG to a Fragment in Android

I have an activity named: ShoppingListActivity in which i have added 3 fragments. For this example i will use only one fragment. In onCreate method i have declared a ViewPager that looks like this:
ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
and a setupViewPager(viewPager); method that looks like this:
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
Fragment shoppingListFragment = new ShoppingListFragment();
getSupportFragmentManager().beginTransaction().add(shoppingListFragment, "ShoppingListFragmentTag").commit();
adapter.addFragment(shoppingListFragment, "SHOPPING LIST");
viewPager.setAdapter(adapter);
}
My ViewPagerAdapter class lookslike this:
private class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> fragmentList = new ArrayList<>();
private final List<String> fragmentTitleList = new ArrayList<>();
ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return fragmentList.get(position);
}
#Override
public int getCount() {
return fragmentList.size();
}
void addFragment(Fragment fragment, String title) {
fragmentList.add(fragment);
fragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return fragmentTitleList.get(position);
}
}
My problem is when i go from ShoppingListActivity to another activity and than come back, my fragments are not refreshed. This is my code from onResume method in which i try to find the fragment to detach and attach the fragment like this:
FragmentManager fragmentManager = getSupportFragmentManager();
ShoppingListFragment shoppingListFragment = (ShoppingListFragment) fragmentManager.findFragmentByTag("ShoppingListFragmentTag");
fragmentManager.beginTransaction().detach(shoppingListFragment).attach(shoppingListFragment).commit();
The problem is that i get this error: java.lang.IllegalStateException: Can't change tag of fragment ShoppingListFragment{528673f4 #0 ShoppingListFragmentTag}: was ShoppingListFragmentTag now android:switcher:2131558559:0
How can i set the Tag correctly to the fragment?
Thanks in advance!

from the code what I understand is, There is a ViewPager implemented in ShoppingListActivity along with tabs.
In viewpager each fragment contains the list of something which come from server right? Now you want to refresh whole viewpager when user back from the ShoppingListInfoActivity right?
Do below changes in you ShoppinglistActivity.
1) Declare ViewPagerAdapter adapter; at class level global.
2)change private class ViewPagerAdapter extends FragmentPagerAdapter
replace FragmentPagerAdapter to FragmentStatePagerAdapter
3) change in onresume()
#Override
protected void onResume() {
super.onResume();
if(adapter!=null){
adapter.notifyDataSetChanged();
}
}

Viewpager with Tablayout not working proper

Here i am getting result like...
Activity start..
at at that time these two fragments calls
-> Fragment 1 load
-> Fragment 2 load in background
swapping right (means going from frag 1 to fragment 2)
at that time I am in fragment two and same time
-> Fragment 3 load in background
swapping in right (means going from Frag 2 to 3 then)
--> there is nothing issue.
HERE IS MY CODE
Main Activity
#Override
protected void onCreate(Bundle savedInstanceState) {
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 OneFragment(), "ONE");
adapter.addFragment(new TwoFragment(), "TWO");
adapter.addFragment(new ThreeFragment(), "THREE");
viewPager.setAdapter(adapter);
}
This is my adapter class
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();
}
// add fragment
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
// for title
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
And there is 3 fragment right now there is nothing into that fragment .....

ViewPager setOffscreenPageLimit default is 1
Please view this link
Visit Documentation
Update
Please Override this method of fragment
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
// load data here
}else{
// fragment is no longer visible
}
}

Use this tutorial..this may helps you
http://www.androidhive.info/2015/09/android-material-design-working-with-tabs/
you need not include this lines in your onCreate Method (Remove this lines)
viewPager.setCurrentItem(0);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
By default,Viewpager will set '0' for starting index..

Replace your code with this. This runs well on my app :
#Override
protected void onCreate(Bundle savedInstanceState) {
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
assert tabLayout != null;
tabLayout.setupWithViewPager(viewPager);
tabLayout.setSelected(true);
}
And no need to add viewPager.setCurrentItem(0);
Because by default ViewPager will be set to the Starting index of 0. As already told by Ajay Jayendran.
Hope this will works. (:

In tab view I want to refresh Fragment every change

viewPager = (ViewPager) findViewById(R.id.tabanim_viewpager);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabanim_tabs);
setupViewPager(viewPager);
tabLayout.setupWithViewPager(viewPager);
public void setupViewPager(ViewPager upViewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new ViewTodayFragment(),"Daily");
adapter.addFrag(new ViewWeekFragment(),"Weekly");
adapter.addFrag(new ViewMonthFragment(),"Monthly");
adapter.addFrag(new ViewYearFragment(),"Yearly");
viewPager.setAdapter(adapter);
}
I want to refresh fragment every time when tab changing.
inside fragment this is my code
public class ViewTodayFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
RecyclerView recyclerView;
RecyclerView.LayoutManager mLayoutManager;
RecyclerView.Adapter mAdapter;
// TODO: Rename and change types of parameters
View v;
ListView listview;
private ArrayList<DailyModel> mItems;
public static String datesel="a";
public ViewTodayFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
v=inflater.inflate(R.layout.fragment_view_today, container, false);
recyclerView =(RecyclerView)v.findViewById(R.id.view_today_lv_today);
recyclerView.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(mLayoutManager);
loadData();
return v;
}
#Override
public void onResume() {
super.onResume();
loadData();
}
public void loadData(){
mItems=new ArrayList<DailyModel>();
List<Income> ll = null;
Log.d("ALLL",datesel);
if(datesel.equals("a")){
Calendar cw = Calendar.getInstance();
SimpleDateFormat format1 = new SimpleDateFormat("dd-MM-yyyy");
String currentDay=format1.format(cw.getTime());
ll=new IncomeHandler(getActivity()).getIncomeByThisDay(currentDay);
}else{
ll=new IncomeHandler(getActivity()).getIncomeByThisDay(datesel);
}
for (int i = 0; i < ll.size(); i++) {
DailyModel a=new DailyModel();
a.setCategory(ll.get(i).getWay());
a.setDescription(ll.get(i).getDes());
a.setType(ll.get(i).getType());
a.setBank("Bank");
a.setAmount(ll.get(i).getAmount());
mItems.add(a);
}
mAdapter = new DailyAdapter(mItems);
recyclerView.setAdapter(mAdapter);
}
}
So like this there are 4 tabs so i want to refresh every time it change the tab.I try to do that inside OnResume().But it also not working.

Create your pager adapter like this.
class PagerAdapter extends FragmentPagerAdapter {
private final List<String> fragmentTitleList = new ArrayList<>();
public PagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
public void addFragmentTitle(String title) {
fragmentTitleList.add(title);
}
#Override
public Fragment getItem(int position) {
if (position == 0) {
return new ViewTodayFragment();
} else if (position == 1) {
return new ViewWeekFragment();
} else if(position == 2){
return new ViewMonthFragment();
} else{
return new ViewYearFragment();
}
}
#Override
public int getCount() {
return 4;
}
#Override
public CharSequence getPageTitle(int position) {
return fragmentTitleList.get(position);
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
}
Now you need to add fragment like this
PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager());
adapter .addFragmentTitle("Daily");
//..... add rest of the fragment title.
viewPager.setAdapter(pagerAdapter );
hope this will help you. though i didn't try this. just writing please let me know if you get any error.

I solved this type issue currently.Please reffer my Code line by line.it might be Help you.
Thanks.
ViewPager viewPager;
ViewPagerAdapter adapter;
viewPager = (ViewPager) findViewById(R.id.tabanim_viewpager);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabanim_tabs);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabanim_tabs);
setupViewPager(viewPager);
tabLayout.setupWithViewPager(viewPager);
viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageSelected(int position) {
adapter.getItem(position).onResume();
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
public void setupViewPager(ViewPager upViewPager) {
adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new ViewTodayFragment(),"Daily");
adapter.addFrag(new ViewWeekFragment(),"Weekly");
adapter.addFrag(new ViewMonthFragment(),"Monthly");
adapter.addFrag(new ViewYearFragment(),"Yearly");
viewPager.setAdapter(adapter);
}

Implement ViewPager.OnPageChangeListener http://developer.android.com/reference/android/support/v4/view/ViewPager.OnPageChangeListener.html

I solved a similar problem. My four tabs (a sports timer with athletes - skiers or cyclsits - starting at intervals) also needed to communicate with each other. For example once a race is started, the set up controls must be disabled.
My project was based on Google's SlidingTabsColors sample.
I created a simple, one method interface called Refreshable and each of my tabs (Fragments) implemented its refresh method.
In my SlidingTabsFragment (extends Fragment) I override instantiateItem so I can capture a reference to each tab's fragment.
// Here we can safely save a reference to the created
// Fragment, no matter where it came from (either getItem() or
// FragmentManger).
//
#Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment createdFragment = (Fragment) super.instantiateItem(container, position);
/**
* Save Fragment references in an array with the MainActivity
* so that other tabs can be refreshed (state updated) depending on
* changes to other tabs.
*/
MainActivity a = (MainActivity)getActivity();
a.addFragment((Refreshable)createdFragment);
return createdFragment;
}
My main is an observer of my data model, but yours may different.
This is the main's method to "register" the fragments.
/**
* Accepts the specified fragment and adds to the list of "Refreshable" Fragments.
* If it is already registered, it is not added a second time.
*
* #param fragment
* the Fragment (Observer) to add.
*/
public void addFragment(Refreshable fragment) {
if (fragment == null) {
throw new NullPointerException("fragment == null");
}
synchronized (this) {
if (!mRefreshables.contains(fragment))
mRefreshables.add(fragment);
}
}
In my case, this code is in the update method of my Observer. My data has changed (race started, interval countdown expired, finisher recorded) and I can refresh all tabs. I cannot call from one tab to another because of race (no pun intended) conditions.
/**
* Call refresh on every Fragment to update state.
*/
for (Refreshable refreshable : array) {
refreshable.refresh();
}
Each tab's refresh method does its own thing.
You may not need an Observer co-ordinating all tabs, but at least you'll have a reference to them and a method other than onResume (which didn't work for me either) to call and have the content refresh itself.

your answer....you must use
viewPager.setAdapter(adapter);
when your selected tab is change.

FragmentPagerAdapter always load the next fragment instead the current

#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_dictionary);
getWindow().setSoftInputMode(
WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
setupNavMenu();
}
private void setupViewPager(ViewPager viewPager) {
adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new A(), "A");
adapter.addFragment(new B(), "B");
adapter.addFragment(new C(), "C");
adapter.addFragment(new D(), "D");
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);
}
}
The problem is:
When I starts the activity, i get the first fragment's view(A), BUT the next fragment(B) loads without the view, so when I slide to the next view(B), i get the view that i'v been loaded at the previous fragment, so now It's load fragment C...
the problem is that fragment B's content depends on the input in fragment A (data saved is sharedpreferences) so I allways get the default value at fragment B because it was loaded in fragment A.
The bug works the same way when I'm in the fragment D, so when I'll slide left to fragment C, it will show fragment C AND loads fragment B also.

its not a bug its the default functionality of a viewpager. for each nth page (n-1)th and (n+1)th page loads automatically with the nth page. I don't think there is any straight forward way to achieve what you want.

The best way would be to use a custom onSwipeListener instead of ViewPager and load the fragment yourself..
But for ViewPager you can use a hack:
After saving data in fragment A,
viewPager.setAdapter(adapter);
which will reload all fragments.
Don't forget to first save the current pager position.
after reset, set pager position so you don't go back to the first position every time.
not good coding but it should work.

on your ViewPagerAdapter. override method : getItemPosition : return POSITION_NONE

Access TextView in ViewPager from Activity

I have an Activity with a ViewPager containing multiple fragments. how can i now access a TextView in one of that fragments to change its text from the main activity? I tried multiple ways and they all ended in a NullPointerException.
Activity:
public class SummonerOverview extends SherlockFragmentActivity implements TabListener, OnPageChangeListener {
private ViewPager mPager;
private PagerAdapter mAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.summoner_overview);
initialize();
}
private void initialize() {
// initialize Pager
mPager = (ViewPager) findViewById(R.id.viewpager);
mAdapter = new PagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mAdapter);
mPager.setCurrentItem(1);
mPager.setOnPageChangeListener(this);
}
}
PagerAdapter:
public class PagerAdapter extends FragmentPagerAdapter {
public PagerAdapter(FragmentManager fm) {
super(fm);
frags = new Fragment[3];
frags[0] = new StatisticsFragment(0);
frags[1] = new RatingsFragment(1);
frags[2] = new HistoryFragment(2);
}
private final int NUM_PAGES = 3;
Fragment[] frags;
#Override
public Fragment getItem(int arg0) {
if (arg0 == 0)
return frags[0];
else if (arg0 == 1)
return frags[1];
else
return frags[2];
}
#Override
public int getCount() {
return NUM_PAGES;
}
}
The Fragment:
public class StatisticsFragment extends SherlockFragment {
public StatisticsFragment(int fragNr) {
this.fragNr = fragNr;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_overview_statistics, container, false);
return v;
}
}
The Textview in the StatisticsFragment is labeled with an id in the fragment_overview_statistics.xml, but when i try
TextView tv = (TextView) findViewById(R.id.id_of_the_textview)
tv.setText("text");
from within the onCreate() Method of the Activity after the initialize() Method, i get an Exception.

Okay, after another hour of googling, i think i solves my own question (although i'm sure there is a better method to solve that)
I now hold all the Data that is displayed by the fragments in the MainActivity and make the Fragmets consume this Data in their onCreateView() Method by using public Methods of the Activity.
In the PagerAdapter, i overwrote getItemPosition() to:
public int getItemPosition(Object object) {
return POSITION_NONE;
}
Now, everytime i update some of the Data, i also call mAdapter.notifyDataSetChanged() which leads into a recreation of all fragments.
It works, although it looks like a poor hack for me. Im sure there must be a better solution because now i have to recreate all fragments for changing one TextView of one Fragment, what is surely not the way it is intended to be done.