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Android ViewPager2 RecyclerView notifyDataSetChanged() not working

I'm using ViewPager2 and RecyclerView develop to Search activity.
What I want is use text entered in EditText as request parameter and response data is reflected in the RecyclerView.
I checked that the data was responded normally, but it was not reflected in the view.
I read so many questions and posts, but I couldn't solve the problem that the view was not refreshed.
Upon checking, data was added to the list of RecyclerView, the methods of the RecyclerView Adapter were not executed at all.
SearchActivity
public class SearchActivity extends AppCompatActivity {
private ActivitySearchBinding binding;
private static final int[] TAB_TITLES = new int[]{R.string.tab_text_1, R.string.tab_text_2};
private final String key;
private BusStopInterface busStopInterface;
private PlaceholderFragment fragment;
private SectionsPagerAdapter sectionsPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivitySearchBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
sectionsPagerAdapter = new SectionsPagerAdapter(SearchActivity.this);
ViewPager2 pager = binding.viewPager;
pager.setAdapter(sectionsPagerAdapter);
TabLayout tabs = binding.tabs;
EditText searchBox = binding.searchBox;
fragment = new PlaceholderFragment();
new TabLayoutMediator(tabs, pager, (tab, position) -> tab.setText(TAB_TITLES[position])).attach();
RetrofitClient retrofitClient = RetrofitClient.getInstance();
busStopInterface = RetrofitClient.getRetrofitInterface();
searchBox.addTextChangedListener(textWatcher);
pager.registerOnPageChangeCallback(pageChangeCallback);
}
ViewPager2.OnPageChangeCallback pageChangeCallback = new ViewPager2.OnPageChangeCallback() {
#Override
public void onPageSelected(int position) {
super.onPageSelected(position);
if (position == 0) {
Log.d("position", "Bus stop");;
} else if (position == 1) {
Log.d("position", "Bus");;
}
}
};
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) {
}
#Override
public void afterTextChanged(Editable s) {
busStopInterface.getBusStop(key, 25, "json", 25, s.toString()).enqueue(new Callback<Example>() {
#Override
public void onResponse(Call<Example> call, Response<Example> response) {
if (response.isSuccessful()) {
Example example = response.body();
Items items = example.getResult().getBody().getItems(); //I checked the data response.
fragment.resetRecyclerView(items.getItem());
sectionsPagerAdapter.notifyDataSetChanged();
Log.d("retrofit", "Data fetch success");
} else {
Log.d("retrofit", "Data fetch fail");
}
}
#Override
public void onFailure(Call<Example> call, Throwable t) {
Log.d("retrofit", t.getMessage());
}
});
}
};
}
PlaceholderFragment
public class PlaceholderFragment extends Fragment {
private static final String ARG_SECTION_NUMBER = "section_number";
private PageViewModel pageViewModel;
private FragmentSearchBinding binding;
public List<BusStopItem> items = new ArrayList<>();
public SearchRecyclerViewAdapter adapter = new SearchRecyclerViewAdapter(items);
public static PlaceholderFragment newInstance(int index) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle bundle = new Bundle();
bundle.putInt(ARG_SECTION_NUMBER, index);
fragment.setArguments(bundle);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
pageViewModel = new ViewModelProvider(this).get(PageViewModel.class);
int index = 1;
if (getArguments() != null) {
index = getArguments().getInt(ARG_SECTION_NUMBER);
}
pageViewModel.setIndex(index);
}
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
binding = FragmentSearchBinding.inflate(inflater, container, false);
View root = binding.getRoot();
pageViewModel.getIndex().observe(getViewLifecycleOwner(), new Observer<Integer>() {
#Override
public void onChanged(Integer index) {
if (index == 1) {
adapter.setItemViewType(SearchRecyclerViewAdapter.VIEWTYPE_BUS_STOP);
} else if (index == 2) {
adapter.setItemViewType(SearchRecyclerViewAdapter.VIEWTYPE_BUS);
}
}
});
return root;
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
RecyclerView recyclerView = binding.searchRecyclerView;
recyclerView.setAdapter(adapter);
recyclerView.addItemDecoration(new DividerItemDecoration(recyclerView.getContext(), 1));
}
#Override
public void onDestroyView() {
super.onDestroyView();
binding = null;
}
public void resetRecyclerView(List<BusStopItem> newItems) {
items.clear();
items.addAll(newItems);
adapter.notifyDataSetChanged();
}
}
SearchRecyclerViewAdapter
public class SearchRecyclerViewAdapter extends RecyclerView.Adapter<SearchRecyclerViewAdapter.ViewHolder> {
public static final int VIEWTYPE_BUS_STOP = 0;
public static final int VIEWTYPE_BUS = 1;
int mItemViewType;
List<BusStopItem> busStopItems;
public class ViewHolder extends RecyclerView.ViewHolder {
TextView busStopName, busStopId, busStopLocation, busName, busArea, busRoute;
public ViewHolder(#NonNull View itemView) {
super(itemView);
busStopName = itemView.findViewById(R.id.busStopName);
busStopId = itemView.findViewById(R.id.busStopId);
busStopLocation = itemView.findViewById(R.id.busStopLocation);
busName = itemView.findViewById(R.id.busName);
busArea = itemView.findViewById(R.id.busArea);
busRoute = itemView.findViewById(R.id.busRoute);
}
public void setBusStopItem(BusStopItem item) {
busStopName.setText(item.getNodenm());
if(item.getNodeno() != null) {
busStopId.setText(item.getNodeno().toString());
}
}
}
public SearchRecyclerViewAdapter(List<BusStopItem> busStopItems) {
this.busStopItems = busStopItems;
}
public void setItemViewType(int viewType) {
mItemViewType = viewType;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
Context context = parent.getContext();
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view = null;
if (viewType == VIEWTYPE_BUS_STOP) {
view = inflater.inflate(R.layout.search_bus_stop_item, parent, false);
} else if (viewType == VIEWTYPE_BUS) {
view = inflater.inflate(R.layout.search_bus_item, parent, false);
}
SearchRecyclerViewAdapter.ViewHolder vh = new SearchRecyclerViewAdapter.ViewHolder(view);
return vh;
}
#Override
public int getItemViewType(int position) {
return mItemViewType;
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
if (mItemViewType == VIEWTYPE_BUS_STOP) {
holder.setBusStopItem(busStopItems.get(position));
} else if (mItemViewType == VIEWTYPE_BUS) {
}
}
#Override
public int getItemCount() {
return busStopItems.size();
}
}
SectionsPagerAdapter
public class SectionsPagerAdapter extends FragmentStateAdapter {
public SectionsPagerAdapter(FragmentActivity fa) {
super(fa);
}
#NonNull
#Override
public Fragment createFragment(int position) {
return PlaceholderFragment.newInstance(position + 1);
}
#Override
public int getItemCount() {
return 2;
}
}
What I tried
public void resetRecyclerView(List<BusStopItem> newItems) {
items.clear();
items.addAll(newItems);
adapter.notifyDataSetChanged();
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.detach(this).attach(this).commit();
}
java.lang.NullPointerException: Attempt to invoke virtual method 'androidx.fragment.app.FragmentTransaction androidx.fragment.app.FragmentManager.beginTransaction()' on a null object reference

You create PlaceholderFragment but not add it to FragmmentManger.
fragment = new PlaceholderFragment();
When `busStopInterface.getBusStop()` get return, you set data to
private PlaceholderFragment fragment
and fragment is not attach to any Activity,so UI dosen't refresh. You should get PlaceholderFragment instance from SectionsPagerAdapter or create PlaceholderFragment instance for SectionsPagerAdapter, and you can set data to real PlaceholderFragment
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivitySearchBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
fragments = new ArrayList<>();
fragments.add(PlaceholderFragment.newInstance(1));
fragments.add(PlaceholderFragment.newInstance(2));
sectionsPagerAdapter = new SectionsPagerAdapter(SearchActivity.this, fragments);
ViewPager2 pager = binding.viewPager;
pager.setAdapter(sectionsPagerAdapter);
TabLayout tabs = binding.tabs;
EditText searchBox = binding.searchBox;
new TabLayoutMediator(tabs, pager, (tab, position) -> tab.setText(TAB_TITLES[position])).attach();
RetrofitClient retrofitClient = RetrofitClient.getInstance();
busStopInterface = RetrofitClient.getRetrofitInterface();
searchBox.addTextChangedListener(textWatcher);
pager.registerOnPageChangeCallback(pageChangeCallback);
}
public class SectionsPagerAdapter extends FragmentStateAdapter {
private final List<PlaceholderFragment> fragments;
public SectionsPagerAdapter(FragmentActivity fa, List<PlaceholderFragment> fragments) {
super(fa);
this.fragments = fragments;
}
#NonNull
#Override
public Fragment createFragment(int position) {
return fragments.get(position);
}
#Override
public int getItemCount() {
return 2;
}
}
busStopInterface.getBusStop(key, 25, "json", 25, s.toString()).enqueue(new Callback<Example>() {
#Override
public void onResponse(Call<Example> call, Response<Example> response) {
if (response.isSuccessful()) {
Example example = response.body();
Items items = example.getResult().getBody().getItems(); //I checked the data response.
fragments.get(1).resetRecyclerView(items.getItem());
Log.d("retrofit", "Data fetch success");
} else {
Log.d("retrofit", "Data fetch fail");
}
}
#Override
public void onFailure(Call<Example> call, Throwable t) {
Log.d("retrofit", t.getMessage());
}
});
PS. remove
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.detach(this).attach(this).commit();

How to send input from searchview which is in an activity to fragment which is in the view pager of that activity

So i have a searchview placed in an activity which has a tablayout and viewpager.In the viewpager there is a fragment for each tab with a textview.What im trying to do is to get the input from the searchview and set the text of the textview with that input and i cant seem to be able to do it.I tried to put the input from the searchview in a bundle(this being done in the activity),and then get the arguments in the fragment in onCreateView() but the problem is that the activity and the fragment are being created simultaneously wthich means that the input from the searchview would be null.
This is the Activity:
public class SearchActivity extends AppCompatActivity {
TabLayout tabLayout;
ViewPager viewPager;
ViewPagerAdapter viewPagerAdapter;
SearchView searchView;
Toolbar toolbar;
ImageButton imageButtonBack;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
bindUI();
viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
viewPagerAdapter.AddFragment(new NewestFragment(), "Newest"); // this line can cause crashes
viewPagerAdapter.AddFragment(new OldestFragment(), "Oldest"); // this line can cause crashes
viewPager.setAdapter(viewPagerAdapter);
tabLayout.setupWithViewPager(viewPager);
setSearchView();
setImageButtonBack();
}
private void setSearchView() {
searchView.requestFocus();
View v = searchView.findViewById(R.id.search_plate);
v.setBackgroundColor(Color.parseColor("#ffffff"));
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String query) {
Bundle bundle = new Bundle();
bundle.putString("searchViewText", searchView.getQuery().toString());
NewestFragment newestFragment = new NewestFragment();
OldestFragment oldestFragment = new OldestFragment();
newestFragment.setArguments(bundle);
oldestFragment.setArguments(bundle);
searchView.clearFocus();
return false;
}
#Override
public boolean onQueryTextChange(String newText) {
Bundle bundle = new Bundle();
bundle.putString("searchViewText", searchView.getQuery().toString());
NewestFragment newestFragment = new NewestFragment();
OldestFragment oldestFragment = new OldestFragment();
newestFragment.setArguments(bundle);
oldestFragment.setArguments(bundle);
return false;
}
});
}
private void bindUI() {
imageButtonBack = findViewById(R.id.back);
tabLayout = findViewById(R.id.tabs);
viewPager = findViewById(R.id.view_pager);
searchView = findViewById(R.id.search_view_searchactivity);
toolbar = findViewById(R.id.toolbar_selected_category);
}
private void setImageButtonBack() {
imageButtonBack.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
finish();
}
});
}
}
The adapter of the ViewPager:
public class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> fragmentList = new ArrayList<>(); // this line can cause crashes
private final List<String> titlesList = new ArrayList<>();
public ViewPagerAdapter(#NonNull FragmentManager fragmentManager) {
super(fragmentManager);
}
#NonNull
#Override
public Fragment getItem(int position) {
return fragmentList.get(position);
}
#Override
public int getCount() {
return titlesList.size();
}
#Nullable
#Override
public CharSequence getPageTitle(int position) {
return titlesList.get(position);
}
public void AddFragment(Fragment fragment, String title) {
fragmentList.add(fragment); // this line can cause crashes
titlesList.add(title);
}
#Override
public void notifyDataSetChanged() {
super.notifyDataSetChanged();
}
}
And here is the fragment:
public class NewestFragment extends Fragment {
View view;
TextView textView;
public NewestFragment(){
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
view=inflater.inflate(R.layout.fragment_search_newest, container, false);
textView=view.findViewById(R.id.tttttttttttttttttttt);
try {
String searchViewText=getArguments().getString("searchViewText");
textView.setText(searchViewText);
}
catch (Exception e){
//something
}
return view;
}
}

The fragments are attached to activity so first activity is created lets leave that but I think you should use a MVVM pattern and create viewmodel and then you can observe the search view and update the fragment textview using that viewmodel class
https://codelabs.developers.google.com/codelabs/kotlin-android-training-live-data/index.html#0

To change the fragments that are created by a FragmentPagerAdapter, you should use a DynamicFragmentPagerAdapter. Refer to the following code below.
public class DynamicFragmentPagerAdapter extends PagerAdapter {
private static final String TAG = "DynamicFragmentPagerAdapter";
private final FragmentManager fragmentManager;
public static abstract class FragmentIdentifier implements Parcelable {
private final String fragmentTag;
private final Bundle args;
public FragmentIdentifier(#NonNull String fragmentTag, #Nullable Bundle args) {
this.fragmentTag = fragmentTag;
this.args = args;
}
protected FragmentIdentifier(Parcel in) {
fragmentTag = in.readString();
args = in.readBundle(getClass().getClassLoader());
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(fragmentTag);
dest.writeBundle(args);
}
protected final Fragment newFragment() {
Fragment fragment = createFragment();
Bundle oldArgs = fragment.getArguments();
Bundle newArgs = new Bundle();
if(oldArgs != null) {
newArgs.putAll(oldArgs);
}
if(args != null) {
newArgs.putAll(args);
}
fragment.setArguments(newArgs);
return fragment;
}
protected abstract Fragment createFragment();
}
private ArrayList<FragmentIdentifier> fragmentIdentifiers = new ArrayList<>();
private FragmentTransaction currentTransaction = null;
private Fragment currentPrimaryItem = null;
public DynamicFragmentPagerAdapter(FragmentManager fragmentManager) {
this.fragmentManager = fragmentManager;
}
private int findIndexIfAdded(FragmentIdentifier fragmentIdentifier) {
for (int i = 0, size = fragmentIdentifiers.size(); i < size; i++) {
FragmentIdentifier identifier = fragmentIdentifiers.get(i);
if (identifier.fragmentTag.equals(fragmentIdentifier.fragmentTag)) {
return i;
}
}
return -1;
}
public void addFragment(FragmentIdentifier fragmentIdentifier) {
if (findIndexIfAdded(fragmentIdentifier) < 0) {
fragmentIdentifiers.add(fragmentIdentifier);
notifyDataSetChanged();
}
}
public void removeFragment(FragmentIdentifier fragmentIdentifier) {
int index = findIndexIfAdded(fragmentIdentifier);
if (index >= 0) {
fragmentIdentifiers.remove(index);
notifyDataSetChanged();
}
}
#Override
public int getCount() {
return fragmentIdentifiers.size();
}
#Override
public void startUpdate(#NonNull ViewGroup container) {
if (container.getId() == View.NO_ID) {
throw new IllegalStateException("ViewPager with adapter " + this
+ " requires a view id");
}
}
#SuppressWarnings("ReferenceEquality")
#NonNull
#Override
public Object instantiateItem(#NonNull ViewGroup container, int position) {
if (currentTransaction == null) {
currentTransaction = fragmentManager.beginTransaction();
}
final FragmentIdentifier fragmentIdentifier = fragmentIdentifiers.get(position);
// Do we already have this fragment?
final String name = fragmentIdentifier.fragmentTag;
Fragment fragment = fragmentManager.findFragmentByTag(name);
if (fragment != null) {
currentTransaction.attach(fragment);
} else {
fragment = fragmentIdentifier.newFragment();
currentTransaction.add(container.getId(), fragment, fragmentIdentifier.fragmentTag);
}
if (fragment != currentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}
#Override
public void destroyItem(#NonNull ViewGroup container, int position, #NonNull Object object) {
if (currentTransaction == null) {
currentTransaction = fragmentManager.beginTransaction();
}
currentTransaction.detach((Fragment) object);
}
#SuppressWarnings("ReferenceEquality")
#Override
public void setPrimaryItem(#NonNull ViewGroup container, int position, #NonNull Object object) {
Fragment fragment = (Fragment) object;
if (fragment != currentPrimaryItem) {
if (currentPrimaryItem != null) {
currentPrimaryItem.setMenuVisibility(false);
currentPrimaryItem.setUserVisibleHint(false);
}
fragment.setMenuVisibility(true);
fragment.setUserVisibleHint(true);
currentPrimaryItem = fragment;
}
}
#Override
public void finishUpdate(#NonNull ViewGroup container) {
if (currentTransaction != null) {
currentTransaction.commitNowAllowingStateLoss();
currentTransaction = null;
}
}
#Override
public boolean isViewFromObject(#NonNull View view, #NonNull Object object) {
return ((Fragment) object).getView() == view;
}
#Override
public Parcelable saveState() {
Bundle bundle = new Bundle();
bundle.putParcelableArrayList("fragmentIdentifiers", fragmentIdentifiers);
return bundle;
}
#Override
public void restoreState(Parcelable state, ClassLoader loader) {
Bundle bundle = ((Bundle)state);
bundle.setClassLoader(loader);
fragmentIdentifiers = bundle.getParcelableArrayList("fragmentIdentifiers");
}
}

Cannot Cast Activity to Interface in fragment

my code has Class Cast Exception error.
When the string is sent from the adapter to the fragment by interface. In the fragment, the interface goes to the specific activity if the particular string is selected.
this is Interface code:
public interface StringListener {
void sendStr(String title);
}
and so this is adapter code:
public class StringRecyclerViewAdapter extends RecyclerView.Adapter<StringRecyclerViewAdapter.MyViewHolder>{
List<GridSubject> subjects;
Context context;
public StringRecyclerViewAdapter(Context context,List<GridSubject> subjects)
{
this.context=context;
this.subjects=subjects;
}
#NonNull
#Override
public MyViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view;
LayoutInflater inflater=LayoutInflater.from(context);
view=inflater.inflate(R.layout.custom_layout,parent,false);
return new MyViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull MyViewHolder holder, int position) {
final GridSubject subject=subjects.get(position);
holder.txts.setText(subject.text);
holder.imgs.setImageResource(subject.drwab);
holder.myCard.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
sendStrMe(subject.getText());
}
});
}
#Override
public int getItemCount() {
return subjects.size();
}
public void sendStrMe(String title) {
StringListener listener=(StringListener) context;
listener.sendStr(title);
}
class MyViewHolder extends RecyclerView.ViewHolder{
TextView txts;
ImageView imgs;
CardView myCard;
public MyViewHolder(View itemView) {
super(itemView);
txts=itemView.findViewById(R.id.txt);
imgs=itemView.findViewById(R.id.img);
myCard=itemView.findViewById(R.id.my_card);
}
}
and this is Fragment Code:
public class FragmentA extends Fragment implements SportListener {
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
public Intent intent;
public FragmentA() {
// Required empty public constructor
}
public static FragmentA newInstance(String param1, String param2) {
FragmentA fragment = new FragmentA();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.my_layout_sport, container, false);
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
try {
super.onActivityCreated(savedInstanceState);
RecyclerView recyclerView=getView().findViewById(R.id.recycler_me);
final String[] txts={"Special","Hard","Manual","Easy"};
int[] imgs={R.drawable.special,R.drawable.hard,R.drawable.manual,R.drawable.easy};
List<GridSubject> subjects=new ArrayList<>();
for(int i=0;i<imgs.length;i++) {
subjects.add(new GridSubject(txts[i], imgs[i]));
}
int ori=getResources().getConfiguration().orientation;
int span;
if(ori== Configuration.ORIENTATION_LANDSCAPE)
span=3;
else
span=2;
StringRecyclerViewAdapter adapter=new StringRecyclerViewAdapter(getActivity(),subjects);
recyclerView.setLayoutManager(new GridLayoutManager(getActivity(),span));
recyclerView.setAdapter(adapter);
}
catch (Exception e)
{
Toast.makeText(getActivity().getApplicationContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
}
}
#Override
public void onDetach() {
super.onDetach();
}
#Override
public void sendSport(String title) {
if(title=="Special") {
intent=new Intent(getActivity(),WebActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
}
else{
intent=new Intent(getActivity(),SportShowActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
}
startActivity(intent);
}
}
and this is Activity code:
public class MainActivity extends AppCompatActivity {
BottomNavigationView btm_navs;
FragmentA afrag;
FragmentB bfrag;
FragmentC cfrag;
FragmentD dfrag;
ViewPager pagerS;
MenuItem menuItem;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btm_navs = findViewById(R.id.btn_navs);
pagerS = findViewById(R.id.view_pager_mes);
btm_navs.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.item_a:
pagerS.setCurrentItem(0);
break;
case R.id.item_b:
pagerS.setCurrentItem(1);
break;
case R.id.item_c:
pagerS.setCurrentItem(2);
break;
case R.id.item_d:
pagerS.setCurrentItem(3);
break;
}
return true;
}
});
pagerS.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
if (menuItem != null) {
menuItem.setChecked(false);
}
else {
btm_navs.getMenu().getItem(position).setChecked(false);
}
btm_navs.getMenu().getItem(position).setChecked(true);
menuItem = btm_navs.getMenu().getItem(position);
}
#Override
public void onPageScrollStateChanged(int state) {
}
});
setupViewPager();
}
catch (Exception e)
{
Toast.makeText(this, e.getMessage(), Toast.LENGTH_LONG).show();
}
}
public void setupViewPager()
{
ViewPageradapter pageradapter=new ViewPageradapter(getSupportFragmentManager());
afrag=new FragmentA();
bfrag=new FragmentB();
cfrag =new FragmentC();
dfrag=new FragmentD();
pageradapter.addFragment(afrag);
pageradapter.addFragment(bfrag);
pageradapter.addFragment(cfrag);
pageradapter.addFragment(dfrag);
pagerS.setAdapter(pageradapter);
}
}
and so these are errors:
java.lang.ClassCastException: com.example.project.MainActivity cannot be cast to com.example.project.StringListener
at com.example.pakhkhsh.StringRecyclerViewAdapter.sendStrMe(StringRecyclerViewAdapter.java:56)
at com.example.pakhkhsh.StringRecyclerViewAdapter$1.onClick(StringRecyclerViewAdapter.java:45)
at android.view.View.performClick(View.java:4756)
at android.view.View$PerformClick.run(View.java:19749)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Your activity needs to implement SportListener, not the fragment.
just do it:
public class MainActivity extends AppCompatActivity implements SportListener {
// your code ...
}```

Android fragment lifecycle added more items into List on pressing back button

As i'm using FragNav library i have some items into List and when i switching on other fragment and after pressing on BackButton i have some other items into this List,
for example generally i have 1 item into List with RecyclerView after switching on other fragment and pressing back button on phone i have 2 items into RecyclerView and using onSaveInstanceState,
onActivityCreated couldn't resolve my problem
my Fragment:
public class HomeFragment extends BaseFragment implements IAnimationListener, View.OnClickListener, InstagramFeedsAdapter.OnClickListener {
...
// constructor
public static HomeFragment createInstance(int instance) {
HomeFragment fragment = new HomeFragment();
Bundle bundle = new Bundle();
bundle.putInt(BaseFragment.ARGS_INSTANCE, instance);
fragment.setArguments(bundle);
return fragment;
}
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
mView = inflater.inflate(R.layout.instagram_post_container, container, false);
activity = getActivity();
context = getActivity().getBaseContext();
mediaUrls = new ArrayList<>();
feedsSchema = new FeedsSchema();
feedsSchema.setId(1);
mediaUrls.add("http://gizasystems.com/wp-content/uploads/2014/08/natural-world-hero3.jpg");
feedsSchema.setFeed_media_url(mediaUrls);
feedsSchema.setFollowers_count(10);
feedsSchema.setFollowings_count(20);
feedsSchema.setPage_name("my test");
feedsSchema.setType(FeedsSchema.feed_types.IMAGE);
items.add(feedsSchema);
instagram_feeds = mView.findViewById(R.id.instagram_feeds);
layoutManager = new LinearLayoutManager(context);
instagram_feeds.setLayoutManager(layoutManager);
instagram_feeds.setNestedScrollingEnabled(false);
instagramFeedsAdapter = new InstagramFeedsAdapter(activity, context, this, items);
return mView;
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Bundle arguments = getArguments();
}
#Override
public void onAnimationEnd() {
}
#Override
public void onClick(View view) {
int clickedItem = view.getId();
}
#Override
public void onStart() {
super.onStart();
}
#Override
public void onResume() {
super.onResume();
}
#Override
public void onPause() {
super.onPause();
}
#Override
public void onStop() {
super.onStop();
}
#Override
public void onItemClick(View view, String transitionName, int position) {
}
#Override
public void onSaveInstanceState(#NonNull Bundle outState) {
super.onSaveInstanceState(outState);
outState.putParcelableArrayList("someVarA", new ArrayList<>(items));
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (savedInstanceState != null)
items = savedInstanceState.getParcelableArrayList("someVarA");
}
}
and my Adapter:
public class InstagramFeedsAdapter extends RecyclerView.Adapter<InstagramFeedsAdapter.InstagramFeedsViewHolder>
implements PreviewView.OnPreviewChangeListener {
private OnClickListener listener;
private List<FeedsSchema> feedsItems;
private Context context;
private boolean hoveredOnPopup = false;
private ExoPlayerManager exoPlayerManager;
private Activity activity;
private enum feedType {
IMAGE,
IMAGESLIDER,
VIDEO
}
public InstagramFeedsAdapter(Activity activity, Context context, OnClickListener listener, List<FeedsSchema> items) {
this.listener = listener;
this.feedsItems = items;
this.context = context;
this.activity = activity;
}
#Override
public void onBindViewHolder(#NonNull final InstagramFeedsViewHolder holder, int position) {
int feedType = feedsItems.get(position).getType().ordinal();
implementingGeneralViewData(holder, position);
if (feedType == 0) {
if (feedsItems.get(position).getFeed_media_url().size() > 1) {
implementingImageSliderView(holder, position);
} else {
implementingImageView(holder, position);
}
} else {
implementingVideoPlayerView(holder, position);
}
}
private void implementingVideoPlayerView(InstagramFeedsViewHolder holder, int position) {
}
#SuppressLint("CheckResult")
private void implementingImageSliderView(final InstagramFeedsViewHolder holder, final int position) {
}
#SuppressLint("CheckResult")
private void implementingImageView(final InstagramFeedsViewHolder holder, final int position) {
}
#Override
public int getItemCount() {
return feedsItems.size();
}
public class InstagramFeedsViewHolder extends RecyclerView.ViewHolder
implements View.OnClickListener, PopupInflaterListener, PopupStateListener, PopupOnHoverListener {
...
public InstagramFeedsViewHolder(View itemView) {
super(itemView);
itemView.setOnClickListener(this);
ButterKnife.bind(this, itemView);
}
#Override
public void onClick(View view) {
}
public void bind(int position) {
...
}
}

RecyclerView.Adapter onClick

I am having trouble implementing view.OnClickListener in my RecyclerView.Adapter. I am trying to implement multi-pane layout (landscape tablet layout version with RecyclerView and detail side by side). I have so far created this Activity:
public class MovieListActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_movie_list);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
MovieListFragment movieListFragment = new MovieListFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.recycler_view_fragment, movieListFragment);
transaction.addToBackStack(null);
transaction.commit();
}
}
which starts a Fragment:
public class MovieListFragment extends Fragment {
#BindView(R.id.recyclerView)
RecyclerView mRecyclerView;
private MoviesAdapter mAdapter;
public MovieListFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAdapter = new MoviesAdapter(getContext());
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_movie_list, container, false);
ButterKnife.bind(this,view);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
mRecyclerView.setAdapter(mAdapter);
return view;
}
#Override
public void onStart() {
super.onStart();
getPopularMovies();
}
private void getPopularMovies() {
RestAdapter restAdapter = new RestAdapter.Builder()
.setEndpoint("http://api.themoviedb.org")
.setLogLevel(RestAdapter.LogLevel.FULL)
.build();
MoviesApiService service = restAdapter.create(MoviesApiService.class);
service.getPopularMovies(new Callback<Movie.MovieResult>() {
#Override
public void success(Movie.MovieResult movieResult, Response response) {
mAdapter.setMovieList(movieResult.getResults());
}
#Override
public void failure(RetrofitError error) { error.printStackTrace(); }
});
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
}
#Override
public void onDetach() {
super.onDetach();
}
}
which calls the RecyclerView.Adapter:
public class MoviesAdapter extends RecyclerView.Adapter<MovieViewHolder> {
private List<Movie> mMovieList;
private LayoutInflater mInflater;
private Context mContext;
public MoviesAdapter(Context context) {
this.mContext = context;
this.mInflater = LayoutInflater.from(context); //
}
#Override
public MovieViewHolder onCreateViewHolder(ViewGroup parent, final int viewType) {
View view = mInflater.inflate(R.layout.movie_row_item, parent, false);
final MovieViewHolder viewHolder = new MovieViewHolder(view);
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
int position = viewHolder.getAdapterPosition();
Intent intent = new Intent(mContext, MovieDetailActivity.class);
intent.putExtra(MovieDetailActivity.MOVIE_EXTRA, mMovieList.get(position));
mContext.startActivity(intent);
}
});
return viewHolder;
}
#Override
public void onBindViewHolder(MovieViewHolder holder, int position) {
Movie movie = mMovieList.get(position);
Picasso.with(mContext)
.load(movie.getPoster())
.placeholder(R.color.colorAccent)
.into(holder.thumbnail);
holder.movieTitle.setText(movie.getTitle());
holder.rating.setText(movie.getRating());
}
#Override
public int getItemCount() {
return (mMovieList == null) ? 0 : mMovieList.size();
}
public void setMovieList(List<Movie> movieList) {
this.mMovieList = new ArrayList<>();
this.mMovieList.addAll(movieList);
notifyDataSetChanged();
}
}
Here in onClick I need to decide whether to start a new Activity (like in my code) or update content of detail Fragment (in my tablet landscape layout).
According to this link, you should decide based on fact if your DetailFragment is != null in activity like this:
public void onItemSelected(int position) {
DisplayFragment displayFrag = (DisplayFragment) getFragmentManager()
.findFragmentById(R.id.display_frag);
if (displayFrag == null) {
// DisplayFragment (Fragment B) is not in the layout (handset layout),
// so start DisplayActivity (Activity B)
// and pass it the info about the selected item
Intent intent = new Intent(this, DisplayActivity.class);
intent.putExtra("position", position);
startActivity(intent);
} else {
// DisplayFragment (Fragment B) is in the layout (tablet layout),
// so tell the fragment to update
displayFrag.updateContent(position);
}
}
But I'm not able to check this in Adapter. Any help would be highly appreciated!
Thank you.

Created the custom interface click action to get the control in fragment class
i hope it will works for you
public class MoviesAdapter extends RecyclerView.Adapter {
MoviesAdapterCallback moviesAdapterCallback;
private List<Movie> mMovieList;
private LayoutInflater mInflater;
private Context mContext;
public MoviesAdapter(Context context,MoviesAdapterCallback moviesAdapterCallback) {
this.mContext = context;
this.moviesAdapterCallback =moviesAdapterCallback;
this.mInflater = LayoutInflater.from(context); //
}
#Override
public MovieViewHolder onCreateViewHolder(ViewGroup parent, final int viewType) {
View view = mInflater.inflate(R.layout.movie_row_item, parent, false);
final MovieViewHolder viewHolder = new MovieViewHolder(view);
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
/* int position = viewHolder.getAdapterPosition();
Intent intent = new Intent(mContext, MovieDetailActivity.class);
intent.putExtra(MovieDetailActivity.MOVIE_EXTRA, mMovieList.get(position));
mContext.startActivity(intent);
*/ moviesAdapterCallback.MovieClicked(view);
}
});
return viewHolder;
}
#Override
public void onBindViewHolder(MovieViewHolder holder, int position) {
Movie movie = mMovieList.get(position);
Picasso.with(mContext)
.load(movie.getPoster())
.placeholder(R.color.colorAccent)
.into(holder.thumbnail);
holder.movieTitle.setText(movie.getTitle());
holder.rating.setText(movie.getRating());
}
#Override
public int getItemCount() {
return (mMovieList == null) ? 0 : mMovieList.size();
}
public void setMovieList(List<Movie> movieList) {
this.mMovieList = new ArrayList<>();
this.mMovieList.addAll(movieList);
notifyDataSetChanged();
}
public interface MoviesAdapterCallback {
void MovieClicked(View view);
}
}
in Fragment Class
public class MovieListFragment extends Fragment {
#BindView(R.id.recyclerView)
RecyclerView mRecyclerView;
private MoviesAdapter mAdapter;
public MovieListFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_movie_list, container, false);
ButterKnife.bind(this,view);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
mAdapter = new MoviesAdapter(getContext(), new MoviesAdapter.MoviesAdapterCallback(){
#Override
public void MovieClicked(View view) {
DisplayFragment displayFrag = (DisplayFragment) getFragmentManager()
.findFragmentById(R.id.display_frag);
if (displayFrag == null) {
// DisplayFragment (Fragment B) is not in the layout (handset layout),
// so start DisplayActivity (Activity B)
// and pass it the info about the selected item
Intent intent = new Intent(this, DisplayActivity.class);
intent.putExtra("position", position);
startActivity(intent);
} else {
// DisplayFragment (Fragment B) is in the layout (tablet layout),
// so tell the fragment to update
displayFrag.updateContent(position);
}
}
});
mRecyclerView.setAdapter(mAdapter);
return view;
}
#Override
public void onStart() {
super.onStart();
getPopularMovies();
}
private void getPopularMovies() {
RestAdapter restAdapter = new RestAdapter.Builder()
.setEndpoint("http://api.themoviedb.org")
.setLogLevel(RestAdapter.LogLevel.FULL)
.build();
MoviesApiService service = restAdapter.create(MoviesApiService.class);
service.getPopularMovies(new Callback<Movie.MovieResult>() {
#Override
public void success(Movie.MovieResult movieResult, Response response) {
mAdapter.setMovieList(movieResult.getResults());
}
#Override
public void failure(RetrofitError error) { error.printStackTrace(); }
});
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
}
#Override
public void onDetach() {
super.onDetach();
}
}