Develop Reference

How to retrieve state of recyclerview in a fragment from a bundle?

I have an activity HomeActivity where I navigate between two fragments Fragment1 and Fragment2. The Fragment1 fragment contains a recyclerview. When I move to Fragment2, Fragment1 is paused and stopped. When I come back to Fragment1, the list loads again. How to return to the scroll position from which I left? One way which I have tried is to save the state of recyclerview in a bundle before the fragment is paused in onPause() method. Now, how do I use this save state when view is created?
The navigation code is:
final NavController navController = Navigation.findNavController(this, R.id.nav_controller);
binding.go_to_fragment2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
navController.navigate(R.id.fragment2);
}
});
binding.go_to_fragment1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
navController.navigate(R.id.fragment1);
}
});
The code for Fragment1 is:
public class Friends extends Fragment1 {
private FriendsFragmentBinding binding;
private MyAdapter myAdapter;
private static Bundle RecyclerState;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container,
#Nullable Bundle savedInstanceState) {
binding = FriendsFragmentBinding.inflate(inflater, container, false);
binding.mRecycler.setHasFixedSize(true);
binding.mRecycler.setLayoutManager(new LinearLayoutManager(getContext()));
PagedList.Config config = new PagedList.Config.Builder()
.setEnablePlaceholders(false)
.setPrefetchDistance(2)
.setPageSize(5)
.build();
// Init Adapter Configuration
Query mQuery = FirebaseFirestore.getInstance().collection("posts");
FirestorePagingOptions<Post> options = new FirestorePagingOptions.Builder<Post>()
.setLifecycleOwner(this)
.setQuery(mQuery, config, Post.class)
.build();
binding.swipe.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
myAdapter.refresh();
}
});
myAdapter = new MyAdapter(options, new MyAdapter.GetState() {
#Override
public void thisState(boolean state) {
if (state) {
binding.swipe.setRefreshing(true);
} else {
binding.swipe.setRefreshing(false);
}
}
});
binding.mRecycler.setAdapter(myAdapter);
return binding.getRoot();
}
#Override
public void onPause() {
super.onPause();
Parcelable listState = Objects.requireNonNull(binding.mRecycler.getLayoutManager()).onSaveInstanceState();
RecyclerState = new Bundle();
RecyclerState.putParcelable("key", listState);
}
}

You're calling binding.mRecycler.setAdapter(myAdapter); before your adapter has any data set. It is when your adapter is set that the saved scroll position is restored. Since there's no items in your adapter, there's nothing to scroll back to, so your scroll position is lost.
As per the Restore RecyclerView scroll position blog post, you have two options:
Don't set your adapter until you get data for the first time.
Upgrade to RecyclerView 1.2.0-alpha02 or higher and switch the StateRestorationPolicy to PREVENT_WHEN_EMPTY:
adapter.stateRestorationPolicy = PREVENT_WHEN_EMPTY
Which will mean that the RecyclerView will wait until your adapter is populated with data before restoring its state, thereby restoring your scroll position correctly.

Android Studio - Update RecyclerView from Dialog Fragment in Menu Item

Hey guys I really need your help. I've spent like 5 days trying to get my recyclerview to update only when the user presses OK on a dialogbox, that appears from the menu actionbar. I've tried every possible method I could think of, every method I've seen on stackoverflow, YouTube, etc. and none of them worked for me.
How do I get the recyclerview in a fragment to update after dialogbox closes? I know there are similar questions regarding updating the menu, and (recyclerviews with dialogfragments), but none of them have a combination.
Out of the countless attempts, the current code configuration posted below isn't causing any errors, however, the recyclerview remains blank. The closest attempt I had to finding a solution, was creating an adapter and setting up the recycler in onOptionsItemSelected. But obviously, it updates only when the user clicks the button, and the initial click would create a blank recyclerview.
Fragment:
(There's a lot of repeated commented code from different attempts)
public class ExerciseRoutine extends Fragment implements ExerciseRoutine_Dialog.RoutineDialogListener{
private String Routine_name, Routine_split;
private ArrayList<ExerciseRoutine_Information> Routine_information = new ArrayList<>();
private RecyclerView recyclerView;
private RecyclerView.Adapter adapter;
private RecyclerView.LayoutManager layoutManager;
#Override
public void sendInput(String name, String split, RecyclerView.Adapter DialogAdapter) {
Routine_name = name;
Routine_split = split;
adapter = DialogAdapter;
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.exercise_routine_fragment, container, false);
//Report that this fragment would like to participate in populating the options menu by
//receiving a call to onCreateOptionsMenu(Menu, MenuInflater) and related methods.
//If true, the fragment has menu items to contribute.
setHasOptionsMenu(true);
recyclerView = view.findViewById(R.id.ExerciseRoutine_Recycler);
//BuildRecyclerView();
//recyclerView.setHasFixedSize(true); //If the Recyclerview is static
/*Routine_information.add(new ExerciseRoutine_Information(Routine_name, Routine_split));
recyclerView = view.findViewById(R.id.ExerciseRoutine_Recycler);
//recyclerView.setHasFixedSize(true); //If the Recyclerview is static
layoutManager = new LinearLayoutManager(getActivity());
adapter = new ExerciseRoutineAdapter(Routine_information);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setAdapter(adapter);*/
return view;
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.exercise_routine_menu, menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()){
case R.id.action_addRoutine:
ExerciseRoutine_Dialog routineDialog = new ExerciseRoutine_Dialog();
routineDialog.setTargetFragment(ExerciseRoutine.this, 1);
routineDialog.show(getFragmentManager(), "Routine Dialog");
//Routine_information.add(new ExerciseRoutine_Information(Routine_name, Routine_split));
BuildRecyclerView();
//adapter.notifyItemInserted(Routine_information.size());
//if(!Routine_name.equals("") && !Routine_split.equals("")) {
//}
}
return super.onOptionsItemSelected(item);
}
public void BuildRecyclerView(){
layoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(layoutManager);
recyclerView.setAdapter(adapter);
}
public void BuildAdapter(){
//adapter = new ExerciseRoutineAdapter(getContext(),Routine_information);
adapter.notifyItemInserted(Routine_information.size());
}
}
My Dialog Fragment:
public class ExerciseRoutine_Dialog extends DialogFragment{
private TextView ActionOK, ActionCANCEL;
private EditText Routine_name, Routine_split;
private RoutineDialogListener activityCommander;
private ArrayList<ExerciseRoutine_Information> Routine_information = new ArrayList<>();
private RecyclerView.Adapter adapter;
public interface RoutineDialogListener{
void sendInput(String name, String split, RecyclerView.Adapter DialogAdapter);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
try{
activityCommander = (RoutineDialogListener) getTargetFragment();
}catch(ClassCastException e){
throw new ClassCastException(context.toString() + "Must Implement RoutineDialogListener");
}
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.exercise_routine_dialog, container, false);
Routine_name = view.findViewById(R.id.ExerciseRoutine_DialogNameInput);
Routine_split = view.findViewById(R.id.ExerciseRoutine_DialogSplitInput);
ActionOK = view.findViewById(R.id.ExerciseRoutine_DialogAction_OK);
ActionCANCEL = view.findViewById(R.id.ExerciseRoutine_DialogAction_CANCEL);
//recyclerView = view.findViewById(R.id.ExerciseRoutine_Recycler);
ActionCANCEL.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
getDialog().dismiss();
}
});
ActionOK.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String name = Routine_name.getText().toString();
String split = Routine_split.getText().toString();
if(!name.equals("") && !split.equals("")) {
Routine_information.add(new ExerciseRoutine_Information(name, split));
adapter = new ExerciseRoutineAdapter(getContext(), Routine_information);
activityCommander.sendInput(name, split, adapter);
adapter.notifyItemInserted(Routine_information.size());
}
getDialog().dismiss();
}
});
return view;
}
}

Your current approach seems to be to pass the RecyclerView.Adapter to the DialogFragment and try to insert the new data on-the-spot. I think this is a problematic setup. The dialog's purpose is to offer some means for the users to enter the required data, period. It should not be tasked with the job of managing the RecyclerView or its Adapter because that way your components will be very tightly coupled:
Imagine that first you use a ListView in your implementation, and suddenly someone decides to ban every ListView from your app (maybe for performance reasons) and has you exchange them all for RecyclerViews. Then your approach would force you to change the code for the DialogFragment (it would have to cater to a different type of Adapter). A more loosely coupled implementation would enable you to make changes to one component without having to rewrite too many others.
That's why I won't try to make your code work as-is, instead I'd like to show you another way:
Because the RecyclerView is part of the Fragment's UI, the Fragment is the place where code related to managing the RecyclerView belongs. It is basically possible to have the Adapter as an inner class of the Fragment but I prefer having it as a standalone class if the code gets a little longer, and also because it enforces "decoupling".
Interfaces play a very important part in good architecture, so the DialogFragment will still make use of an interface to send its data. But it's up to the class which actually implements the interface (here: the Fragment) to pass the data to any interested third parties, e.g. the RecyclerView.Adapter (The Adapter in turn could have its own interface to publish important events like clicks on list items).
Having said that, here are some code snippets:
The DialogFragment
public class ExerciseRoutine_Dialog extends DialogFragment {
private EditText Routine_name, Routine_split;
public interface RoutineDialogListener{
/**
* There is some new ExerciseRoutine_Information
*/
void sendInput(String name, String split);
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.exercise_routine_dialog, container, false);
Routine_name = view.findViewById(R.id.ExerciseRoutine_DialogNameInput);
Routine_split = view.findViewById(R.id.ExerciseRoutine_DialogSplitInput);
TextView actionOK = view.findViewById(R.id.ExerciseRoutine_DialogAction_OK);
TextView actionCANCEL = view.findViewById(R.id.ExerciseRoutine_DialogAction_CANCEL);
actionCANCEL.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
getDialog().dismiss();
}
});
actionOK.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String name = Routine_name.getText().toString();
String split = Routine_split.getText().toString();
if(!name.equals("") && !split.equals("")) {
// just send the input to the main Fragment
RoutineDialogListener listener = getListener();
if(listener != null) {
listener.sendInput(name, split);
}
}
getDialog().dismiss();
}
});
return view;
}
/**
* Tries to find a suitable listener, examining first the hosting Fragment (if any) and then the Activity.
* Will return null if this fails
* #return x
*/
private RoutineDialogListener getListener(){
RoutineDialogListener listener;
try{
Fragment onInputSelected_Fragment = getTargetFragment();
if (onInputSelected_Fragment != null){
listener = (RoutineDialogListener) onInputSelected_Fragment;
}
else {
Activity onInputSelected_Activity = getActivity();
listener = (RoutineDialogListener) onInputSelected_Activity;
}
return listener;
}catch(ClassCastException e){
Log.e("Custom Dialog", "onAttach: ClassCastException: " + e.getMessage());
}
return null;
}
}
The Fragment:
public class ExerciseRoutine extends Fragment implements ExerciseRoutine_Dialog.RoutineDialogListener{
public static final String ROUTINE_DIALOG = "Routine Dialog";
private ArrayList<ExerciseRoutine_Information> routineInformations = new ArrayList<>();
private RecyclerView.Adapter adapter;
public static ExerciseRoutine instance(){
return new ExerciseRoutine();
}
#Override
public void sendInput(String name, String split) {
routineInformations.add(new ExerciseRoutine_Information(name, split));
adapter.notifyItemInserted(routineInformations.size());
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.exercise_routine_fragment, container, false);
setHasOptionsMenu(true);
RecyclerView recyclerView = view.findViewById(R.id.ExerciseRoutine_Recycler);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(layoutManager);
adapter = new ExerciseRoutineAdapter(getContext(), routineInformations);
// So far you have a RecyclerView with an empty List.
recyclerView.setAdapter(adapter);
return view;
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.exercise_routine_menu, menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()){
case R.id.action_addRoutine:
showDialog();
return true;
}
return super.onOptionsItemSelected(item);
}
private void showDialog(){
ExerciseRoutine_Dialog routineDialog = new ExerciseRoutine_Dialog();
routineDialog.setTargetFragment(ExerciseRoutine.this, 1);
routineDialog.show(getFragmentManager(), ROUTINE_DIALOG);
}
}

Android - RecyclerView multiplies itself every time device is rotated

I have a landscape configuration for one of my app's activities. This activity contains a fragment and this fragment contains one textview and one recyclerview. Everytime when i switch in between portrait and landscape modes, the recyclerview leaves the view of itself like however it was before i turned the device. It might be a little difficult to understand what i try to ask here, so i recorded a gif for that.
https://giphy.com/gifs/3Wv7NAtT8ezP1SQhDu
This is my activity
public class RecipeStepsActivity extends AppCompatActivity {
static Recipe recipe;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recipe_steps);
if (StepDetailActivity.SDA_TAG.equals(StepDetailActivity.NEGATIVE))
recipe = getIntent().getParcelableExtra("recipe");
Bundle b = new Bundle();
b.putParcelable("recipe", recipe);
ActionBar ab = getSupportActionBar();
if (ab != null)
ab.setTitle(recipe.getName());
RecipeStepsFragment recipeStepsFragment = new RecipeStepsFragment();
recipeStepsFragment.setArguments(b);
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().add(R.id.frame_layout_steps, recipeStepsFragment).commit();
}
}
This is my fragment
public class RecipeStepsFragment extends Fragment {
#BindView(R.id.recipe_steps_rv)
RecyclerView recyclerView;
#BindView(R.id.ingredients_tv)
TextView tv_ingredients;
List<Step> steps;
public RecipeStepsFragment(){}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_recipe_steps, container, false);
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ButterKnife.bind(this, view);
List<Ingredients> ingredients;
Recipe recipe = getArguments().getParcelable("recipe");
steps = recipe.getSteps();
initRecyclerView();
ingredients = recipe.getIngredients();
String ingredientsAppended = "INGREDIENTS" + "\n\n";
if (ingredients == null){
ingredientsAppended = "Not Available";
} else {
for (int a = 0 ; a < ingredients.size() ; a++) {
Ingredients i = ingredients.get(a);
ingredientsAppended += String.valueOf(i.getQuantity()) + " " +
i.getMeasure() + " " +
i.getIngredient();
if (a+1 != ingredients.size()){
ingredientsAppended += '\n';
}
}
}
tv_ingredients.setText(ingredientsAppended);
if(savedInstanceState != null){
recyclerView.scrollToPosition(savedInstanceState.getInt("position"));
}
}
#Override
public void onSaveInstanceState(#NonNull Bundle outState) {
outState.putInt("position", recyclerView.getVerticalScrollbarPosition());
super.onSaveInstanceState(outState);
}
private void initRecyclerView(){
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
recyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.VERTICAL));
RecipeStepsRecyclerAdapter recipeStepsRecyclerAdapter =
new RecipeStepsRecyclerAdapter(steps, new RecipeStepsRecyclerAdapter.ClickListener() {
#Override
public void onItemClick(int clickedItemPosition) {
Intent intentToStepDetail = new Intent(getActivity(), StepDetailActivity.class);
Step step = steps.get(clickedItemPosition);
intentToStepDetail.putExtra("step", step);
startActivity(intentToStepDetail);
}
}, getContext());
recyclerView.setAdapter(recipeStepsRecyclerAdapter);
recipeStepsRecyclerAdapter.notifyDataSetChanged();
}
}
This is my adapter
public class RecipeStepsRecyclerAdapter extends RecyclerView.Adapter<RecipeStepsRecyclerAdapter.ViewHolder> {
private List<Step> stepList;
private LayoutInflater mInflater;
final private ClickListener clickListener;
public RecipeStepsRecyclerAdapter(List<Step> stepList, ClickListener clickListener, Context context){
this.stepList = stepList;
this.clickListener = clickListener;
mInflater = LayoutInflater.from(context);
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = mInflater.inflate(R.layout.recipe_steps_recyclerview_adapter, parent, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
Step step = stepList.get(position);
String stepContent = step.getShortDescription();
holder.listingNumber.setText(String.valueOf(position+1));
holder.stepContent.setText(stepContent);
}
#Override
public int getItemCount() {
return stepList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
TextView listingNumber;
TextView stepContent;
private ViewHolder(View itemView) {
super(itemView);
listingNumber = itemView.findViewById(R.id.list_number_tv);
stepContent = itemView.findViewById(R.id.step_content_tv);
itemView.setOnClickListener(this);
}
#Override
public void onClick(View view) {
int clickedPosition = getAdapterPosition();
clickListener.onItemClick(clickedPosition);
}
}
public interface ClickListener{
void onItemClick(int clickedItemPosition);
}
}
Layout files are as I already explained above. I guess nothing special to post here.
Thanks in advance.

The problem is that you add a new fragment to the Activity every time it is created. Here's the end of your onCreate(...):
RecipeStepsFragment recipeStepsFragment = new RecipeStepsFragment();
recipeStepsFragment.setArguments(b);
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().add(R.id.frame_layout_steps, recipeStepsFragment).commit();
The FragmentManager keeps a reference to the fragment you add to it even if the host Activity is destroyed. Thus, you keep adding new instances of the RecipeStepsFragment eventually overlaying each other and producing the seen behavior.
Don't worry, the fix is pretty simple: use replace(...) instead of add(...):
fm.beginTransaction().replace(R.id.frame_layout_steps, recipeStepsFragment).commit();
P.S.: Note, however, that replacing the current fragment with a new one every time the host activity is destroyed is not a good idea. You should check either if the savedInstanceState is null (which indicates that it's a non-recreated Activity) or if the given fragment is already added (define a tag when adding the fragment and try finding it in onCreate(...) before replacing the old one).

Every time you change the rotation of the screen your activity is destroyed and recreated. That is the reason why your list is populating with new items each time when you switch between your orientation.
So it's important you only instantiate your objects once, and not keep recreating them each time your app is recreated. Which then adds them to your list.
You can use onSaveInstanceState and onRestoreInstanceState.
If you want your app to allow orientation change, apply logic so your list don't get new items each time when activity is created.

Put configChanges attribute in your activity in menifest file
<activity android:name=".VideoActivity" android:configChanges="keyboardHidden|orientation|screenSize"/>

Refresh recyclerView filled from room with spinner case

I want refresh my data in RecyclerView, when I select some item in spinner. RecyclerView is placed in fragment in tabbed activity, My RecyclerView filled from room with livedata. I create observer for RecyclerView , but I don't understand how I can change my observer or do something else.
May be I need recreate this tab...
Please, tell me what i can do.
When I create new observer I getting new data in RecyclerView, but when I interact with this data, I see that all my old observers are live and react to my actioins.
How I can query another data from database and pass it to observer or create new observer and delete old?
My Fragment
public class AllSitesFragment extends Fragment implements AdapterView.OnItemSelectedListener {
#BindView(R.id.recycler_view)
RecyclerView recyclerView;
#BindView(R.id.tvEmptyMessage)
TextView tvEmptyMessage;
#BindView(R.id.spinner)
Spinner spinner;
private WebSitesViewModel mWebSitesViewModel;
private MyRecViewAdapter adapter;
public AllSitesFragment() {}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_all_sites, container, false);
ButterKnife.bind(this, v);
setHasOptionsMenu(true);
mWebSitesViewModel = ViewModelProviders.of(this).get(WebSitesViewModel.class);
adapter = new MyRecViewAdapter(getContext(), mWebSitesViewModel, AllSitesFragment.this );
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
recyclerView.setAdapter(adapter);
//Observer
mWebSitesViewModel.getAllWebSites().observe(this, new Observer<List<WebSites>>() {
#Override
public void onChanged(#Nullable final List<WebSites> webSites) {
adapter.setWebSites(webSites);
if (adapter.getmWebSites().size() == 0) {
tvEmptyMessage.setText(R.string.not_saved_sites);
tvEmptyMessage.setVisibility(View.VISIBLE);
} else {
tvEmptyMessage.setVisibility(View.INVISIBLE);
}
}
});
spinner.setOnItemSelectedListener(this);
mWebSitesViewModel.getAllWebSites().removeObservers(getActivity());
return v;
}
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
switch (position) {
case 0:
// Refresh
break;
case 1:
//Refresh
break;
}
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
}

You need to filter the results of your getAllWebSites() function in your viewModel, so you need a setter in that viewModel to set/update your filter.
You can do it by using a MutableLiveData variable in your viewModel, which will be used as parameter to filter your Website collection.
This can be done by using a switchMap transformation.
It would be something like this (non-functional, adapt it to your needs) :
ViewModel
public class SitesViewModel extends AndroidViewModel {
private final YourManager yourManager;
private final LiveData<WebSites> webSites;
private final MutableLiveData<YourItem> yourItemFilter;
public SitesViewModel(Application application) {
super(application);
yourManager = new YourManager();
yourItemFilter = new MutableLiveData<>();
webSites = Transformations.switchMap(yourItemFilter, input -> yourManager.getAllWebSites(input));
}
public void setYourItemFilter(YourItem filter) {
yourItemFilter.setValue(filter);
}
public LiveData<WebSites> getAllWebSites() {
return webSites;
}
}
Then in your activity simply set the filter value on item selected :
Activity
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
switch (position) {
case 0:
YourItem item = (YourItem) parent.getItemAtPosition(position);
mWebSitesViewModel.setYourItemFilter(item);
break;
case 1:
...
}
}

Unable to refresh listview data within same fragments used under different tabs

I have implemented tabs functionality via SmartTabLayout library in my android application. At present I have used same fragment as viewpager for both of my tabs. Since, the only difference is the view is that sorting of listitems. Below is my HomeActivity code:
HomeActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
final ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
final SmartTabLayout viewPagerTab = (SmartTabLayout) findViewById(R.id.viewpagertab);
viewPagerTab.setCustomTabView(this);
FragmentPagerItems pages = new FragmentPagerItems(this);
pages.add(FragmentPagerItem.of("Test1", SampleFragment.class));
pages.add(FragmentPagerItem.of("Test2", SampleFragment.class));
FragmentStatePagerItemAdapter adapter = new FragmentStatePagerItemAdapter(
getSupportFragmentManager(), pages);
viewPager.setAdapter(adapter);
viewPager.setCurrentItem(0);
viewPagerTab.setViewPager(viewPager);
}
#Override
public View createTabView(ViewGroup container, int position, PagerAdapter adapter) {
LayoutInflater inflater = LayoutInflater.from(container.getContext());
View tab = inflater.inflate(R.layout.custom_tab_icon_and_notification_mark, container, false);
TextView txtTab=(TextView)tab.findViewById(R.id.txtTitle);
switch (position){
case 0:txtTab.setText("Test1");break;
case 1:txtTab.setText("Test2");break;
default:throw new IllegalStateException("Invalid pos - "+ position);
}
return tab;
}
My SampleFragment.java is as below wherein I do some server request for data and update the listview adapter.
SampleFragment.java
List<Items> lstItems=new ArrayList<>();
static ItemListAdapter mAdapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view= inflater.inflate(R.layout.fragment_sample, container, false);
ListView lstviewItems = (ListView) view.findViewById(R.id.lstItems);
int position = FragmentPagerItem.getPosition(getArguments());
View emptyView=view.findViewById(R.id.emptyList);
lstviewItems.setEmptyView(emptyView);
mAdapter = new ItemsListAdapter(getActivity(),lstItems);
lstviewItems.setAdapter(mAdapter);
switch (position){
case 0:
//JsonObjectRequest
loadItems();
break;
case 1:
//sort the loaded items
break;
}
return view;
}
private void loadItems(){
try {
JsonArrayRequest request = new JsonArrayRequest(Request.Method.GET,url, null,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
lstItems.clear();
for (int i = 0; i < response.length(); i++) {
//Add item to lstItems
}
mAdapter.notifyDataSetChanged();
}
}
});
testApp.getInstance().addToRequestQueue(request);
} catch (Exception ex) {
ex.printStackTrace();
}
}
But even after mAdapter.notifyDataSetChanged() the listview in the current viewPager tab i.e. Test1 tab is not getting refreshed. Whereas when I navigate to Test2 tab, I can see the changes in the listview, where is data has been loaded properly. Below is the screenshot for 2 different tabs.
I've also searched for this problem and found other solution which did not work for me. One of the solution being, adding a refresh method in ItemsAdapter as below:
public void refresh(List<Items> items)
{
this.items = items;
notifyDataSetChanged();
}
and instead of mAdapter.notifyDataSetChanged() I used mAdapter.refresh(lstItems);. But unfortunately it did not work either. How can I possibly overcome this. Please let me know if I have to add furthermore details on this.

I think your problem is here:
mAdapter = new ItemsListAdapter(getActivity(),lstItems);
You create a new instance of ItemsListAdapter and bind it to the listview with
lstviewItems.setAdapter(mAdapter);
The problem is that this adapter is static. So if you create a new instance you destroy the old adapter and the listview of the other tab has not the adapter anymore that updates your data.
EDIT:
I'd recommend to load the data on a central place. Add the response (your data objects) to a manager class. Then implement on every view which using this data a callback (lets say JsonDataChangedCallback). Register the classes which implementing the callback to the manager with Manager.getInstance().registerCallback(). Then every time your data is changed call updateCallbacks() in your manager and all views will be updated. That's the way implemented that process in my app and it works.
Sample Code:
public class CDMMovieManager {
private CDMMovieManager() {
m_Movies = new ArrayList<>();
m_MovieChangedCallbacks = new ArrayList<>();
}
public static synchronized CDMMovieManager getInstance() {
if(ms_Instance == null)
ms_Instance = new CDMMovieManager();
return ms_Instance;
}
public void addMovie(CDMMovie p_Movie) {
m_Movies.add(p_Movie);
notifyCallbacks();
}
/**
* Registers a movie changed callback
*
* #param p_MovieChangedCallback the callback to register
*/
public void registerMovieChangedCallback(IDMMovieChangedCallback p_MovieChangedCallback) {
m_MovieChangedCallbacks.add(p_MovieChangedCallback);
}
/**
* Removes a movie changed callback
*
* #param p_MovieChangedCallback the callback to remove
*/
public void removeMovieChangedCallback(IDMMovieChangedCallback p_MovieChangedCallback) {
m_MovieChangedCallbacks.remove(p_MovieChangedCallback);
}
private void notifyCallbacks() {
for(IDMMovieChangedCallback l_MovieChangedCallback : m_MovieChangedCallbacks) {
l_MovieChangedCallback.onMoviesChanged();
}
}
}
And the implementing Class:
public class CDMBasicMovieFragment extends Fragment implements IDMMovieChangedCallback {
//...
#Override
public void onMoviesChanged() {
m_Adapter.notifyDataSetChanged();
}
}