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java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Iterator java.util.List.iterator()' on a null object reference

I m currently working on a android apps which fetch data from parse server. I wanted to filter my recyclerView by using searchview. But it shows me nothing while search. It gives me error in this line*for (ParseObject parseObject : mRooms){ * Please help me to edit my code regarding this issues.
roomcardrecyclerviewadapter
private List<ParseObject> mRooms = new ArrayList<>();
private ArrayList<ParseObject> filterlist;
private ParseObject room;
private String mSection;
private Context context;
public RoomCardRecyclerViewAdapter(){
super(DIFF_CALLBACK);
}
public static final DiffUtil.ItemCallback<ParseObject> DIFF_CALLBACK = new
DiffUtil.ItemCallback<ParseObject>() {
#Override
public boolean areItemsTheSame(#NonNull ParseObject oldItem, #NonNull ParseObject newItem) {
return oldItem.getObjectId() == newItem.getObjectId();
}
#Override
public boolean areContentsTheSame(#NonNull ParseObject oldItem, #NonNull ParseObject newItem) {
return (oldItem.getUpdatedAt().equals(newItem.getUpdatedAt()) &&
oldItem.getCreatedAt().equals(newItem.getCreatedAt()));
}
};
public RoomCardRecyclerViewAdapter(String section) {
this();
this.mSection = section;
}
public RoomCardRecyclerViewAdapter(Context context, List<ParseObject>arrayList) {
this();
this.context = context;
mRooms = arrayList;
filterlist = (ArrayList<ParseObject>) arrayList;
}
public class RoomViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
protected ImageView mRoomImage;
protected TextView mRoomPrice;
protected TextView mInclusiveOrNot;
protected TextView mPropertyType;
protected TextView mNumOfBeds;
protected TextView mNumOfBaths;
protected TextView mRoomLocation;
private Context context;
public RoomViewHolder(Context context, View itemView) {
super(itemView);
mRoomImage = itemView.findViewById(R.id.room_image);
mRoomPrice = itemView.findViewById(R.id.price_label);
mInclusiveOrNot = itemView.findViewById(R.id.incl_excl_label);
mPropertyType = itemView.findViewById(R.id.propertyType_label);
mNumOfBeds = itemView.findViewById(R.id.num_beds_label);
mNumOfBaths = itemView.findViewById(R.id.details_num_baths_label);
mRoomLocation = itemView.findViewById(R.id.location_label);
this.context = context;
//set onclick listener
itemView.setOnClickListener(this);
}
#Override
public void onClick(View v) {
Log.i("Click event: ", "My room has been clicked.");
int pos = getAdapterPosition();
Intent intent;
ParseObject room = getCurrentList().get(pos);
//create the ParseObject proxy
ParseProxyObject roomProxy = new ParseProxyObject(room);
Toast.makeText(context, room.getString("roomSuburb"), Toast.LENGTH_LONG).show();
//fork to corresponding activity
if(mSection != null) {
Log.i("mSection text: ", "mSection text is: " + mSection);
if (mSection.equals("My Rooms")) {
//start my rooms detail activity
Log.i("My room: ", "Room selected " + roomProxy.getObjectId());
intent = new Intent(context, MyRoomDetailActivity.class);
//add the room to the intent
intent.putExtra("currentSelectedRoomObject", room);
Log.i("Selected room", "Put Extra, " + room);
intent.putExtra("roomObject", roomProxy);
context.startActivity(intent);
}
}else {
Log.i("My room:", "RoomDetailActivity loaded for MyRoomDetail Activity instead");
intent = new Intent(context, RoomDetailActivity.class);
//add the proxy to the intent
intent.putExtra("roomObject", roomProxy);
context.startActivity(intent);
}
}
}
#Override
public RoomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
//inflating the viewholder with the appropriate views
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.room_cardview, parent,
false);
return new RoomViewHolder(parent.getContext(), view);
}
#Override
public void onBindViewHolder(#NonNull RoomViewHolder holder, int position) {
room = getItem(position);
holder.mRoomLocation.setText(room.getString("roomSuburb"));
holder.mRoomPrice.setText(Integer.toString(room.getInt("roomMonthlyRent")));
holder.mInclusiveOrNot.setText(room.getString("roomRentInclusiveOfBills"));
holder.mPropertyType.setText(room.getString("roomPropertyType"));
holder.mNumOfBeds.setText(Integer.toString(room.getInt("roomBedrooms")));
holder.mNumOfBaths.setText(Integer.toString(room.getInt("roomBathrooms")));
#Override
public Filter getFilter(){
return new Filter() {
#Override
protected FilterResults performFiltering(CharSequence charSequence) {
String charString = charSequence.toString();
if (charString.isEmpty()){
room = (ParseObject) mRooms;
}else {
List<ParseObject> filteredList = new ArrayList<>();
for (ParseObject parseObject : mRooms){
if (parseObject.getString("roomSuburb").toLowerCase().contains(charString.toLowerCase())){
filteredList.add(parseObject);
}
}
room = (ParseObject) filteredList;
}
FilterResults filterResults = new FilterResults();
filterResults.values = room;
return filterResults;
}
#Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
room = (ParseObject) filterResults.values;
notifyDataSetChanged();
}
};
}
mainActivity
mHomeSectionsPagerAdapter = new
HomeSectionsPagerAdapter(getSupportFragmentManager());
roomCardRecyclerViewAdapter = new RoomCardRecyclerViewAdapter(this,
mRooms);
mRooms = new ArrayList<>();
// Set up the ViewPager with the sections adapter.
mViewPager = findViewById(R.id.container);
mViewPager.setAdapter(mHomeSectionsPagerAdapter);
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
final ParseQuery<ParseUser> query = ParseUser.getQuery();
//get the search view and set the searchable configuration
SearchManager searchManager = (SearchManager)
getSystemService(Context.SEARCH_SERVICE);
MenuItem item = menu.findItem(R.id.search);
SearchView searchView = (SearchView) MenuItemCompat.getActionView(item);
//assumes the current activity is the searchable activity
searchView.setSearchableInfo(searchManager.getSearchableInfo
(getComponentName());
searchView.setSubmitButtonEnabled(true);
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String query) {
roomCardRecyclerViewAdapter.getFilter().filter(query);
return false;
}
#Override
public boolean onQueryTextChange(String newText) {
roomCardRecyclerViewAdapter.getFilter().filter(newText);
return false;
}
});
return true;
}
#Override
public boolean onSearchRequested() {
//pauseSomeStuff();
//roomCardRecyclerViewAdapter.getFilter().filter(query);
return super.onSearchRequested();
}

I think problem is here:
You haven't shared first lines of MainActivity where you declare your variables. So, I assume that you have some code like this:
List mRooms;
Then I assume that, before assigning value to this mRooms you have passed it to RoomCardRecyclerViewAdapter:
roomCardRecyclerViewAdapter = new RoomCardRecyclerViewAdapter(this, mRooms);
mRooms = new ArrayList<>();
Then you have assigned value to mRooms. That's why you get NPE. You can solve this problem just like this:
mRooms = new ArrayList<>();
roomCardRecyclerViewAdapter = new RoomCardRecyclerViewAdapter(this, mRooms);

Filtering in RealmRecyclerViewAdapter does not hide excluded elements

I'm currently building an app which use a RealmRecyclerViewAdapter for displaying the elements inside Realm.
I was looking into implementing the Filterable interface, which I managed to do (thanks to those answers: Link 1 Link 2) but now I have a side effect: when I'm filtering, the Adapter shows all the elements, even if they doesn't match with the filter. Also, the excluded element does show incorrect information. When I close the SearchView, everything is back to normal.
Here is the Activity when I call the Adapter:
public class MainActivity extends AppCompatActivity {
private Realm realm;
HabitCardAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
setUIMode();
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set the title inside the top bar for this activity.
// I'm not doing it inside the Manifest because it changes the app's name
setTitle(R.string.MainActivityTitle);
// Bottom App Bar setup
BottomAppBar bottomAppBar = findViewById(R.id.bottomAppBar);
cutBottomAppEdge(bottomAppBar); // Diamond shape
// Add listener to Stats button inside the bottom app bar
MenuItem statsMenuItem = bottomAppBar.getMenu().findItem(R.id.statsMenuItem);
statsMenuItem.setOnMenuItemClickListener(item -> {
if(item.getItemId() == R.id.statsMenuItem){
Intent i = new Intent(getApplicationContext(), StatsActivity.class);
startActivity(i);
return true;
}
return false;
});
// FAB button setup
FloatingActionButton fab = findViewById(R.id.fabAddButton);
fab.setOnClickListener(view -> {
Intent intent = new Intent(getBaseContext(), CreateHabitActivity.class);
startActivity(intent);
});
RecyclerView rv = findViewById(R.id.habitCardRecyclerView);
TextView emptyMessage = findViewById(R.id.mainEmptyHabitListMessage);
realm = Realm.getDefaultInstance();
RealmResults<Habit> results = realm.where(Habit.class).sort("id").findAll();
results.addChangeListener(habits -> {
if (habits.size() > 0) {
rv.setVisibility(View.VISIBLE);
emptyMessage.setVisibility(View.GONE);
} else {
emptyMessage.setVisibility(View.VISIBLE);
rv.setVisibility(View.GONE);
}
});
//this is necessarily because it is not changed yet
if (results.size() > 0) {
rv.setVisibility(View.VISIBLE);
emptyMessage.setVisibility(View.GONE);
} else {
emptyMessage.setVisibility(View.VISIBLE);
rv.setVisibility(View.GONE);
}
final LinearLayoutManager layoutManager = new LinearLayoutManager(this);
rv.setLayoutManager(layoutManager);
adapter = new HabitCardAdapter(results, true, this, realm);
rv.setAdapter(adapter);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.top_app_bar_menu, menu);
SearchView searchView = (SearchView) menu.findItem(R.id.searchMenuItem).getActionView();
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String query) {
adapter.getFilter().filter(query);
return false;
}
#Override
public boolean onQueryTextChange(String newText) {
if (adapter != null) {
adapter.getFilter().filter(newText);
return true;
}
return false;
}
});
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.searchMenuItem:
return true;
case R.id.settingMenuItem:
Intent intent = new Intent(getApplicationContext(), SettingsActivity.class);
startActivity(intent); //FIXME: animazione
return true;
case R.id.aboutMenuItem:
MaterialAlertDialogBuilder builder = new MaterialAlertDialogBuilder(this);
builder.setTitle(getString(R.string.about_us_title));
builder.setMessage(getString(R.string.about_us_message));
builder.setIcon(R.drawable.ic_sprout_fg_small);
builder.setPositiveButton("OK", (dialogInterface, i) -> {
dialogInterface.dismiss();
});
builder.show();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/**
* Set the Night/Light UI. On the first run of the app, the user get the Light UI.
*/
private void setUIMode() {
SharedPreferences preferences = getSharedPreferences(SettingsActivity.SHARED_PREFS_FILE, MODE_PRIVATE);
int pref = preferences.getInt(SettingsActivity.SHARED_PREFS_DARK_MODE, AppCompatDelegate.MODE_NIGHT_NO);
AppCompatDelegate.setDefaultNightMode(pref);
}
private void cutBottomAppEdge(BottomAppBar bar) {
BottomAppBarTopEdgeTreatment topEdge = new SproutBottomAppBarCutCornersTopEdge(
bar.getFabCradleMargin(),
bar.getFabCradleRoundedCornerRadius(),
bar.getCradleVerticalOffset());
MaterialShapeDrawable babBackground = (MaterialShapeDrawable) bar.getBackground();
//It requires 1.1.0-alpha10
babBackground.setShapeAppearanceModel(
babBackground.getShapeAppearanceModel()
.toBuilder()
.setTopEdge(topEdge)
.build());
}
#Override
protected void onDestroy() {
super.onDestroy();
realm.removeAllChangeListeners();
realm.close();
}
}
Here is the HabitCardAdapter which extends RealmRecyclerViewAdapter:
public class HabitCardAdapter extends RealmRecyclerViewAdapter<Habit, HabitCardAdapter.ViewHolder> implements Filterable {
Context ct;
OrderedRealmCollection<Habit> list;
Realm mRealm;
public HabitCardAdapter(#Nullable OrderedRealmCollection<Habit> data, boolean autoUpdate, Context context, Realm realm) {
super(data, autoUpdate); //autoUpdate to true
ct = context;
list = data;
mRealm = realm;
}
#Override
public int getItemCount() {
return this.list.size();
}
#NonNull
#Override
public HabitCardAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
//TODO: inflatare diversi tipi di carte a seconda del habitType
View view = inflater.inflate(R.layout.fragment_habit_counter_card, parent, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull HabitCardAdapter.ViewHolder holder, int position) {
final Habit habit = getItem(position);
if (habit != null) {
holder.setHabit(habit);
holder.editHabitButton.setOnClickListener(view -> {
Intent intent = new Intent(ct, EditHabitActivity.class);
intent.putExtra("HABIT_ID", habit.getId());
//TODO: Aggiungere l'animazione
ct.startActivity(intent);
});
holder.checkButton.setOnClickListener(view -> {
int habitId = habit.getId();
int newRepValue = habit.getRepetitions() + 1;
int maxReps = habit.getMaxRepetitions();
Log.d("Testing", newRepValue + " - " + maxReps);
if (newRepValue <= habit.getMaxRepetitions()) {
habit.getRealm().executeTransaction(realm -> {
Habit result = realm.where(Habit.class).equalTo("id", habitId).findFirst();
if (result != null) {
result.setRepetitions(newRepValue);
String newLabel = "Completato " + newRepValue + " volte su " + maxReps;
holder.progressLabel.setText(newLabel);
}
});
}
});
}
}
public void filterResults(String text) {
text = text == null ? null : text.toLowerCase().trim();
if (text == null || "".equals(text)) {
updateData(mRealm.where(Habit.class).sort("id").findAllAsync());
} else {
updateData(mRealm.where(Habit.class).contains("title", text).sort("id").findAllAsync());
}
}
public Filter getFilter() {
HabitFilter filter = new HabitFilter(this);
return filter;
}
private class HabitFilter extends Filter {
private final HabitCardAdapter adapter;
private HabitFilter(HabitCardAdapter adapter) {
this.adapter = adapter;
}
#Override
protected FilterResults performFiltering(CharSequence charSequence) {
return new FilterResults();
}
#Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
adapter.filterResults(charSequence.toString());
}
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView habitTitle;
ProgressBar progressBar;
TextView progressLabel;
ImageButton editHabitButton;
Button checkButton;
public ViewHolder(#NonNull View itemView) {
super(itemView);
habitTitle = itemView.findViewById(R.id.habitCardTitle);
editHabitButton = itemView.findViewById(R.id.counterHabitEditButton);
progressBar = itemView.findViewById(R.id.counterHabitProgressBar);
checkButton = itemView.findViewById(R.id.checkButton);
progressLabel = itemView.findViewById(R.id.counterHabitProgressLabel);
}
void setHabit(Habit habit) {
this.habitTitle.setText(habit.getTitle());
this.progressBar.setProgress(habit.getRepetitions());
this.progressBar.setMax(habit.getMaxRepetitions());
this.progressLabel.setText("Completato " + habit.getRepetitions() + " volte su " + habit.getMaxRepetitions()); //FIXME: sposta la stringa
}
}
}

I don't really know if this is the way to go for this problem, but it's now behaving as expected so I'll share the solution here.
Inside the HabitCardAdapter I added another OrderedRealmCollection<Habit> member, called filteredList, while list holds the whole data. In the costructor both of filteredList and list are tied to the data passed to the constructor, but while filteredList will be modified by the query, list will not (probably putting it to final is the best practice). Then everything in the Adapter will now reference to filteredList instead of list, and when the SearchView is selected and the query is up, filteredList will get the data, and then updateData(filteredList) will be called.
Here is what I changed:
public class HabitCardAdapter extends RealmRecyclerViewAdapter<Habit, HabitCardAdapter.ViewHolder> implements Filterable {
Context ct;
OrderedRealmCollection<Habit> list;
OrderedRealmCollection<Habit> filteredList;
Realm mRealm;
...
}
public HabitCardAdapter(#Nullable OrderedRealmCollection<Habit> data, Context context, Realm realm) {
super(data, true, true);
ct = context;
list = data;
filteredList = data;
mRealm = realm;
setHasStableIds(true);
}
Probably the error was here in getItemCount(), when the filteredListsize was smaller than the list one, but since I didn't have any reference to filteredList, I didn't have any way to change that size, and so the Adapter would continue to show - for example - 6 views while I was querying for 3. Having it as a properly class member it let me make this:
#Override
public int getItemCount() {
return this.filteredList.size();
}
public void filterResults(String text) {
text = text == null ? null : text.toLowerCase().trim();
if (text == null || "".equals(text)) {
filteredList = list;
} else {
filteredList = mRealm.where(Habit.class).beginsWith("title", text, Case.INSENSITIVE).sort("id").findAll();
}
updateData(filteredList);
}

Android Searchview filter recyclerview volley implementation

i am implementing search filter using search view i loaded list
successfully and when i clicked on searchview and type word
application crash below is error is Here's the code :
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
// private static final String url = "http://example.com/OnlineDoctor/mobileapp/doctors_list.php?";
private List<ListItems> listItemses;
private RecyclerView recyclerView;
private MainFilteredAdapter mrecyclerViewAdapter;
private LinearLayoutManager linearLayoutManager;
private static final String TAG = MainActivity.class.getSimpleName();
private RelativeLayout ownerlayout;
private SearchView searchView;
private String logintype, property_id;
private String userid;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.recyclerview);
listItemses = new ArrayList<>();
mrecyclerViewAdapter = new
MainFilteredAdapter(listItemses,getApplicationContext());
linearLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(mrecyclerViewAdapter);
loadRenterList();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
searchView = (SearchView) menu.findItem(R.id.action_search)
.getActionView();
searchView.setSearchableInfo(searchManager
.getSearchableInfo(getComponentName()));
searchView.setMaxWidth(Integer.MAX_VALUE);
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String query) {
mrecyclerViewAdapter.getFilter().filter(query);
return false;
}
#Override
public boolean onQueryTextChange(String query) {
mrecyclerViewAdapter.getFilter().filter(query);
return false;
}
});
return true;
}
public void loadRenterList() {
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
url, null,
new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response) {
JSONArray jsonArray = null;
JSONObject jsonObject = null;
try {
jsonArray = response.getJSONArray("data");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject mjsonObject = (JSONObject) jsonArray.get(i);
ListItems newslist = new ListItems();
newslist.setId(mjsonObject.getString("id"));
listItemses.add(newslist);
mrecyclerViewAdapter.notifyDataSetChanged();
}
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
}
// adapter.notifyDataSetChanged();
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
}
});
AppController.getInstance().addToRequestQueue(jsonObjReq);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
searchView = (SearchView) menu.findItem(R.id.action_search)
.getActionView();
searchView.setSearchableInfo(searchManager
.getSearchableInfo(getComponentName()));
searchView.setMaxWidth(Integer.MAX_VALUE);
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String query) {
mrecyclerViewAdapter.getFilter().filter(query);
return false;
}
#Override
public boolean onQueryTextChange(String query) {
mrecyclerViewAdapter.getFilter().filter(query);
return false;
}
});
return true;
}
public class MainFilteredAdapter extends RecyclerView.Adapter<MainFilteredAdapter.MyViewHolder> implements Filterable {
private List<ListItems> doctorlist;
private List<ListItems> doctorlistFiltered;
Context context;
public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
public TextView spec_name,placeName,property_status;
public ImageView imageView;
LinearLayout lllistrow;
public MyViewHolder(View itemView) {
super(itemView);
property_status = itemView.findViewById(R.id.duration);
spec_name = itemView.findViewById(R.id.spec_name);
placeName = itemView.findViewById(R.id.placeName);
imageView = itemView.findViewById(R.id.placeImage);
lllistrow= itemView.findViewById(R.id.mainHolder);
lllistrow.setOnClickListener(this);
}
#Override
public void onClick(View v) {
int position = getLayoutPosition();
switch (v.getId()) {
case R.id.mainHolder:
break;
}
}
}
public MainFilteredAdapter(List<ListItems> boardList, Context context) {
this.doctorlist = boardList;
this.doctorlistFiltered=boardList;
this.context = context;
}
#Override
public MainFilteredAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext())
.inflate(R.layout.listitem, parent, false);
return new MainFilteredAdapter.MyViewHolder(itemView);
}
#Override
public void onBindViewHolder(MainFilteredAdapter.MyViewHolder holder, int position) {
ListItems listItems = doctorlistFiltered.get(position);
/*Picasso.with(context).load("http://neweraprime.com/SFDS/faculty/Upload/Books/" + newslist.get(position).getThumbnailUrl())
.placeholder(R.drawable.ic_pdffile).error(R.drawable.ic_pdffile).resize(256, 256).onlyScaleDown() //Url of the image to load.
.into(holder.thumbNail);*/
holder.property_status.setText(listItems.getPayment_status());
holder.spec_name.setText(listItems.getAddress());
holder.placeName.setText(listItems.getTitle());
}
#Override
public Filter getFilter()
{
return new Filter() {
#Override
protected FilterResults performFiltering(CharSequence charSequence) {
String charString = charSequence.toString();
if (charString.isEmpty()) {
doctorlistFiltered = doctorlist;
} else {
List<ListItems> filteredList = new ArrayList<>();
for (ListItems row : doctorlist) {
// name match condition. this might differ depending on your requirement
// here we are looking for name or phone number match
if (row.getCity().toLowerCase().contains(charString.toLowerCase()) || row.getAddress().contains(charSequence)) {
filteredList.add(row);
}
}
doctorlistFiltered = filteredList;
}
FilterResults filterResults = new FilterResults();
filterResults.values = doctorlistFiltered;
return filterResults;
}
#Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
doctorlistFiltered = (ArrayList<ListItems>) filterResults.values;
notifyDataSetChanged();
}
};
}
#Override
public int getItemCount() {
if(doctorlist != null){
return doctorlistFiltered.size();
} else {
return 0;
}
}
and here is the error
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
at com.www.homerent.MainFilteredAdapter.getItemCount(MainFilteredAdapter.java:129)
at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:4025)
at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3830)
at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4385)
at android.view.View.layout(View.java:19659)
at android.view.ViewGroup.layout(ViewGroup.java:6075)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1083)
at android.view.View.layout(View.java:19659)
at android.view.ViewGroup.layout(ViewGroup.java:6075)

I'd suspect your problem is here:
#Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
doctorlistFiltered = (ArrayList<ListItems>) filterResults.values;
notifyDataSetChanged();
}
Try using this instead:
#Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
doctorlistFiltered = new ArrayList<ListItems>();
if (filterResults.values != null) {
doctorlistFiltered.addAll((ArrayList<ListItems>) filterResults.values);
}
notifyDataSetChanged();
}
I haven't seen anything that guarantees that filterResults.values does contain a non null value(e.g. in case of an error during filtering).
Ps.:
Adjusting the getItemCount() as metionend in the comments should be a given.

Adapter is not updated on using search view

This is basically a notes app,in which we dynamically add data to our app by taking in title and description from the user,the problem is that when we search about some note by its title then instead of giving the possible notes the data set in the adapter vanishes,the logic is written in my filter() function in the adapter class
MainActivity.java
public class MainActivity extends AppCompatActivity implements SearchView.OnQueryTextListener {
private ArrayList<Notes> list;
private NotesAdapter notesAdapter;//this is our notes adapter
private RecyclerView recyclerView;
private LinearLayoutManager linearLayoutManager;
#Override //
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
list=new ArrayList<>();//this is the list which we have to pass into adapter
recyclerView=findViewById(R.id.rv);
notesAdapter=new NotesAdapter(this,list);
View dialogView= LayoutInflater.from(this).inflate(R.layout.dialog_main,null,false);
final EditText title=dialogView.findViewById(R.id.t);
final EditText description=dialogView.findViewById(R.id.d);
final AlertDialog alertDialog=new AlertDialog.Builder(this)
.setTitle("Enter the details:")
.setCancelable(false)
.setView(dialogView)
.setPositiveButton("add", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
list.add(new Notes(title.getText().toString(),description.getText().toString(),false));
notesAdapter.notifyItemChanged(list.size());
}
})
.setNegativeButton("no", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.dismiss();
}
}).create();
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override // on pressing the fab we will get an alert dialog box where we can add title and description and with the option to add it or not
public void onClick(View view) {
alertDialog.show();
}
});
recyclerView.setAdapter(notesAdapter);
linearLayoutManager=new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false);
recyclerView.setLayoutManager(linearLayoutManager);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
final MenuItem searchItem = menu.findItem(R.id.search);
final SearchView searchView = (SearchView) MenuItemCompat.getActionView(searchItem);
searchView.setOnQueryTextListener(this);
return true;
}``
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.search) {
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public boolean onQueryTextSubmit(String s) {
notesAdapter.filter(s);
return true;
}
#Override
public boolean onQueryTextChange(String s) {
notesAdapter.filter(s);
return true;
}
NotesAdapter.java
public class NotesAdapter extends RecyclerView.Adapter<NotesAdapter.NotesHolder> {
private ArrayList<Notes> arrayList;
private ArrayList<Notes> arrayListCopy;
Context c;
NotesAdapter(Context context,ArrayList<Notes> list){
this.arrayList=list;
this.c=context;
this.arrayListCopy=new ArrayList<>(list);//this is where I store identical list which I get from Adapter
}
public class NotesHolder extends RecyclerView.ViewHolder {
TextView textView;
public NotesHolder(View itemView) {
super(itemView);
textView = itemView.findViewById(R.id.tv);
}
}
#Override
public NotesAdapter.NotesHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new NotesHolder(LayoutInflater.from(c).inflate(R.layout.item_row,parent,false));
}
#Override
public void onBindViewHolder(final NotesAdapter.NotesHolder holder, final int position) {
final Notes currentNote=arrayList.get(position);
holder.textView.setText(currentNote.getTitle());
holder.textView.setOnLongClickListener(new View.OnLongClickListener() {
#Override
public boolean onLongClick(View view) {
arrayList.remove(holder.getAdapterPosition());
notifyItemRemoved(holder.getAdapterPosition());
return true;
}
});
holder.textView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent=new Intent(c,AnotherActivity.class);
intent.putExtra("NAME",currentNote.getDescription());
c.startActivity(intent);
}
});
}
#Override
public int getItemCount() {
return arrayList.size();
}
public void filter(String text){//This is my filter function
arrayList.clear();
if(TextUtils.isEmpty(text)){
arrayList.addAll(arrayListCopy);
}
else{
text=text.toLowerCase();
for(Notes note:arrayListCopy){
if(note.getTitle().toLowerCase().contains(text)){
arrayList.add(note);
}
}
}
notifyDataSetChanged();//the data set is still not updated and instead it vanishes
}
}
As soon as I search something the whole list gets vanished ,where am I missing out on?How should I modify my filter function in adapter class?

Change your getItemCount :
#Override
public int getItemCount() {
return arrayListCopy.size();
}

Try this:
NotesAdapter(Context context,ArrayList<Notes> list){
this.arrayList = new ArrayList<>(list.size());
this.c=context;
this.arrayListCopy=new ArrayList<>(list);//this is where I store identical list which I get from Adapter
}
#Override
public int getItemCount() {
return arrayList.size();
}
public void filter(String text){//This is my filter function
arrayList.clear();
if(text.trim().isEmpty() || text == null){
arrayList.addAll(arrayListCopy);
}
else{
text=text.toLowerCase();
for(Notes note:arrayListCopy){
if(note.getTitle().toLowerCase().contains(text)){
arrayList.add(note);
}
}
}
notifyDataSetChanged();//the data set is still not updated and instead it vanishes
}
Original Answer:
Here you are referencing the same variable (i.e. arrayList and arrayListCopy ) are pointing to the same variable. Instead, initialize arrayList like this inside your constructor:
this.arrayList = new ArrayList<>(arrayListCopy.size());

The problem is that arrayList and arrayListCopy are references to the same list.
NotesAdapter(Context context,ArrayList<Notes> list){
this.arrayList=list;
this.c=context;
this.arrayListCopy=list;
}
Changes done to one of them, will be reflected in both. For example arrayList.clear() will also empty the arrayListCopy list.
What you could do is something like this:
List<Notes> originalList;
NotesAdapter(Context context,ArrayList<Notes> list){
this.arrayList=list;
this.c=context;
this.originalList= new ArrayList<>(list); // create a new List that contains all the elements of `list`.
}
And to filter, do this:
public void filter(String text){
arrayList.clear();
if(text.isEmpty()){
arrayList.addAll(originalList);
} else{
text=text.toLowerCase();
for(Notes note : originalList){
if(note.getTitle().toLowerCase().contains(text)){
arrayList.add(note);
}
}
}
notifyDataSetChanged();
}
It seems that you're adding items to the list inside the MainActivity after you create the adapter which means that you'll have to use some other mechanism for adding new items so that originalList will contain all the items. Something like:
public class NotesAdapter extends RecyclerView.Adapter<NotesAdapter.NotesHolder> {
public void addItem(Notes item){
originalList.add(item);
if(text.isEmpty() || item.getTitle().toLowerCase().contains(text.toLowerCase())){
arrayList.add(item);
}
}
}
Here, text is just a reference to the text variable passed to the filter method.
From MainActivity when a new item is created, do this:
adapter.addItem(new Notes(title.getText().toString(),description.getText().toString(),false));

Why are we using interface to set onClick for View Holders for recycler view in the MainActivity

I am going through a tutorial which is using the Recycler View to display a list of weather for each day for a week.
There are two classes which I am confused in:
ForecastAdapter and MainActivity
Here is the code for the above two classes:
ForecastAdapter.java
public class ForecastAdapter extends RecyclerView.Adapter<ForecastAdapter.ForecastAdapterViewHolder> {
private String[] mWeatherData;
final private ForecastAdapterOnClickListener mClickHandler;
//Why do we need to create an interface here.
public interface ForecastAdapterOnClickListener {
void onClick(String weatherForDay);
}
public ForecastAdapter(ForecastAdapterOnClickListener forecastAdapterOnClickListener) {
mClickHandler = forecastAdapterOnClickListener;
}
public class ForecastAdapterViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
public final TextView mWeatherTextView;
public ForecastAdapterViewHolder(View view) {
super(view);
mWeatherTextView = (TextView) view.findViewById(R.id.tv_weather_data);
view.setOnClickListener(this);
}
#Override
public void onClick(View v) {
int adapterPosition = getAdapterPosition();
String weatherForDay = mWeatherData[adapterPosition];
//Why are we calling onClick from mClickHandler here. Why can't we just display Toast here.
mClickHandler.onClick(weatherForDay);
/*Why can't we just display the Toast from here like this:
Toast.makeText(v.getContext(), weatherForDay, Toast.LENGTH_SHORT).show()
*/
}
}
#Override
public ForecastAdapterViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
Context context = viewGroup.getContext();
int layoutIdForListItem = R.layout.forecast_list_item;
LayoutInflater inflater = LayoutInflater.from(context);
boolean shouldAttachToParentImmediately = false;
View view = inflater.inflate(layoutIdForListItem, viewGroup, shouldAttachToParentImmediately);
return new ForecastAdapterViewHolder(view);
}
#Override
public void onBindViewHolder(ForecastAdapterViewHolder forecastAdapterViewHolder, int position) {
String weatherForThisDay = mWeatherData[position];
forecastAdapterViewHolder.mWeatherTextView.setText(weatherForThisDay);
}
#Override
public int getItemCount() {
if (null == mWeatherData) return 0;
return mWeatherData.length;
}
public void setWeatherData(String[] weatherData) {
mWeatherData = weatherData;
notifyDataSetChanged();
}
}
MainActivity.java
//Why are implementing ForecastAdapterOnClickListener here?
public class MainActivity extends AppCompatActivity implements ForecastAdapter.ForecastAdapterOnClickListener{
private RecyclerView mRecyclerView;
private ForecastAdapter mForecastAdapter;
private TextView mErrorMessageDisplay;
private ProgressBar mLoadingIndicator;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_forecast);
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview_forecast);
mErrorMessageDisplay = (TextView) findViewById(R.id.tv_error_message_display);
LinearLayoutManager layoutManager
= new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setHasFixedSize(true);
mForecastAdapter = new ForecastAdapter(this);
mRecyclerView.setAdapter(mForecastAdapter);
mLoadingIndicator = (ProgressBar) findViewById(R.id.pb_loading_indicator);
loadWeatherData();
}
private void loadWeatherData() {
showWeatherDataView();
String location = SunshinePreferences.getPreferredWeatherLocation(this);
new FetchWeatherTask().execute(location);
}
#Override
public void onClick(String weatherForDay) {
Context context = this;
Toast.makeText(context, weatherForDay, Toast.LENGTH_SHORT)
.show();
}
private void showWeatherDataView() {
mErrorMessageDisplay.setVisibility(View.INVISIBLE);
mRecyclerView.setVisibility(View.VISIBLE);
}
private void showErrorMessage() {
mRecyclerView.setVisibility(View.INVISIBLE);
mErrorMessageDisplay.setVisibility(View.VISIBLE);
}
public class FetchWeatherTask extends AsyncTask<String, Void, String[]> {
#Override
protected void onPreExecute() {
super.onPreExecute();
mLoadingIndicator.setVisibility(View.VISIBLE);
}
#Override
protected String[] doInBackground(String... params) {
if (params.length == 0) {
return null;
}
String location = params[0];
URL weatherRequestUrl = NetworkUtils.buildUrl(location);
try {
String jsonWeatherResponse = NetworkUtils
.getResponseFromHttpUrl(weatherRequestUrl);
String[] simpleJsonWeatherData = OpenWeatherJsonUtils
.getSimpleWeatherStringsFromJson(MainActivity.this, jsonWeatherResponse);
return simpleJsonWeatherData;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
#Override
protected void onPostExecute(String[] weatherData) {
mLoadingIndicator.setVisibility(View.INVISIBLE);
if (weatherData != null) {
showWeatherDataView();
mForecastAdapter.setWeatherData(weatherData);
} else {
showErrorMessage();
}
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.forecast, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_refresh) {
mForecastAdapter.setWeatherData(null);
loadWeatherData();
return true;
}
return super.onOptionsItemSelected(item);
}
}
The adapter, view holder and recycler view is working as expected. We are now supposed to implement Click Handling on the rows of the recycler view. Whenever a particular row is clicked, we are supposed to display a toast.
As you can see, we are implementing OnClickListener in the ForecastAdapterViewHolder and in the onClick function we are calling the onClick of the interface "ForecastAdapterOnClickListener".
In the MainActivity.java, we are implementing this "ForecastAdapterOnClickListener" and then displaying the toast.
Why can't we just display the toast in the onClick that is defined for the "ForecastAdapterViewHolder" class. I have tried it and it works. What is the point of doing what is being done in the code?
Is there some advantage in setting the click listener like that?

Because you'll have to display information afterwards and isn't role of ViewHolder neither Adapter. Activity/fragment must do that.
It's to keep your code organized.