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Android Firebase query return Null

I'm working on a project where there's an activity which contains 3 spinners( Nested). I need the 2nd spinner to have the data based on the selected item of the 1st spinner and the data is retrieved from Firebase
The 1st spinner is going to have all "Gouv" values , the 2nd one is going to have the "Deleg" values where "Gouv" value is equal to the selected item "Gouv" of the 1st spinner .
Here is the code that i tried and i keep get in the log Null .
public class RechCode extends AppCompatActivity {
DatabaseReference spinnerRef;
Query spinnerRefG;
Spinner spinnerG;
Spinner spinnerD;
Spinner spinnerL;
ArrayAdapter<String> adapterG;
ArrayAdapter<String> adapterL;
ArrayAdapter<String> adapterD;
ArrayList<String> spinnerDList;
ArrayList<String> spinnerGList;
ArrayList<String> spinnerLOList;
Query spinnerRefD;
private String ChoixG;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rech_code);
spinnerG = findViewById(R.id.SpinnerGouv);
spinnerD = findViewById(R.id.SpinnerDeleg);
spinnerL = findViewById(R.id.SpinnerLoc);
spinnerRef = FirebaseDatabase.getInstance().getReference().child("CodePostale");
//Query queryD = spinnerG.("state", "CA");
spinnerGList = new ArrayList<>();
spinnerDList = new ArrayList<>();
spinnerLOList = new ArrayList<>();
adapterD= new ArrayAdapter<String>( RechCode.this, android.R. layout. simple_spinner_dropdown_item,spinnerDList);
adapterL= new ArrayAdapter<String>( RechCode.this, android.R. layout. simple_spinner_dropdown_item,spinnerLOList);
adapterG= new ArrayAdapter<String>( RechCode.this, android.R. layout. simple_spinner_dropdown_item,spinnerGList);
spinnerG.setAdapter(adapterG);
spinnerD.setAdapter(adapterD);
spinnerL.setAdapter(adapterL);
ShowdataGouv();
spinnerRefG= FirebaseDatabase.getInstance().getReference("CodePostale").child("Deleg").orderByChild("Gouv").equalTo(ChoixG);
ShowdataDeleg();
spinnerG.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
ChoixG = spinnerGList.get(i);
Toast.makeText(getApplicationContext(), "Gouvernorat:" + ChoixG, Toast.LENGTH_LONG).show();
}
#Override
public void onNothingSelected(AdapterView<?> adapterView) {}
});
Button retour = (Button) findViewById(R.id.return_btn);
retour.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
RetourMenu();
}
});
}
private void ShowdataLoc(String text) {
spinnerRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot1) {
for (DataSnapshot item:snapshot1.getChildren()){
spinnerLOList.add(item.child("Loc").getValue().toString());
}
adapterD.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
private void ShowdataDeleg() {
spinnerRefG.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot2) {
for (DataSnapshot item:snapshot2.getChildren()){
spinnerDList.add(item.child("Deleg").getValue().toString());
}
Log.d("Value","BBBBBBBB"+ snapshot2);
adapterD.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
private void ShowdataGouv() {
spinnerRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot3) {
for (DataSnapshot item:snapshot3.getChildren()){
spinnerGList.add(item.child("Gouv").getValue().toString());
Log.d("Value","AAAAAAAAA"+ snapshot3);
}
adapterG.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
private void RetourMenu() {
Intent intent = new Intent(getApplicationContext(), Menus.class);
startActivity(intent);
}
}

The problem is in the way you construct the query here:
spinnerRefG= FirebaseDatabase.getInstance()
.getReference("CodePostale")
.child("Deleg")
.orderByChild("Gouv")
.equalTo(ChoixG);
You're asking to load child nodes of /CodePostale/Deleg that have a Gouv property with a value of ChoixG. But if we check the screenshot of the data, there is no /CodePostale/Deleg, so no data is returned.
What you want instead is to check the child nodes of /CodePostale and return the ones where their Deleg/Gouv property has a value of ChoixG, which you can do with:
spinnerRefG= FirebaseDatabase.getInstance()
.getReference("CodePostale")
.orderByChild("Deleg/Gouv")
.equalTo(ChoixG);

How to get value from pushed data in Firebase?

In my firebase I have questions and their answers stored. Each answer has an id, which it got from push(). But I am unable to show the list of all the users who have answered the question. Please help.
Here is the code:
ListView listView;
ArrayList<String> answerers = new ArrayList<>();
ArrayAdapter arrayAdapter;
String askedBy, question, likes;
FirebaseAuth mAuth;
DatabaseReference databaseReference;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_answers);
listView = findViewById(R.id.answersListView);
Intent intent = getIntent();
askedBy = intent.getStringExtra("askedBy");
question = intent.getStringExtra("question");
likes = intent.getStringExtra("numberOfLikes");
mAuth = FirebaseAuth.getInstance();
databaseReference = FirebaseDatabase.getInstance().getReference();
databaseReference.child("questions").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
if (snapshot.exists()){
for (DataSnapshot dataSnapshot : snapshot.getChildren()){
if (dataSnapshot.child("question").getValue().toString().equals(question) && dataSnapshot.child("askedBy").getValue().toString().equals(askedBy)
&& dataSnapshot.child("likes").getValue().toString().equals(likes)) {
dataSnapshot.child("answers").getRef().addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshots) {
if (snapshots.exists()){
for (DataSnapshot dataSnapshots : snapshots.getChildren()){
String id = dataSnapshot.getRef().push().getKey();
answerers.add(dataSnapshots.child(id).child("answeredBy").getValue().toString());
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
arrayAdapter = new ArrayAdapter<>(ViewAnswersActivity.this, android.R.layout.simple_list_item_1, answerers);
listView.setAdapter(arrayAdapter);
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
Intent intent1 = new Intent(ViewAnswersActivity.this, AnswerActivity.class);
intent1.putExtra("askedBy", askedBy);
intent1.putExtra("answeredBy", answerers.get(i));
intent1.putExtra("question", question);
intent1.putExtra("numberOfLikes", likes);
startActivity(intent1);
}
});
}
When I am running the app, the listView is coming empty, indicating value hasn't been stored.

Try to set adapter within onDataChange()
#Override
public void onDataChange(#NonNull DataSnapshot snapshots) {
if (snapshots.exists()){
for (DataSnapshot dataSnapshots : snapshots.getChildren()){
String id = dataSnapshot.getRef().push().getKey();
answerers.add(dataSnapshots.child(id).child("answeredBy").getValue().toString());
}
arrayAdapter = new ArrayAdapter<> (ViewAnswersActivity.this, android.R.layout.simple_list_item_1, answerers);
listView.setAdapter(arrayAdapter);
}
}

I have this error : "Can't convert object of type java.lang.String to type com.flashpub.flash.imageSection" and i don't know why

I've created a listView, and since i'm opening one of the item, the application need to fetch all image of the application, but it's doesn't work, i can't figure it out why that's showing me this error.
Thank you for helping !
That's my model on Firebase :
imageSection.java
package com.flashpub.flash;
import java.util.List;
public class imageSection {
String imageUrl;
public imageSection(){
}
public imageSection(String imageUrl) {
this.imageUrl = imageUrl;
}
public String getImageUrl() {
return imageUrl;
}
}
chooseSection.java
package com.flashpub.flash;
import java.util.List;
public class chooseSection {
String sectionn;
public chooseSection() {
}
public chooseSection(String sectionn) {
this.sectionn = sectionn;
}
public String getSectionn() {
return sectionn;
}
}
chooseSectionActivity.java
public class ChooseSectionActivity extends AppCompatActivity {
ListView listView;
FirebaseListAdapter<chooseSection> adapter;
chooseSection sectionChosse;
//private HashMap<Integer, String> allItemsList = new HashMap<Integer, String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_choose_section);
listView = findViewById(R.id.listView);
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference();
myRef.keepSynced(true);
Query query = FirebaseDatabase.getInstance().getReference().child("Sections");
Log.i("salut", query.toString());
FirebaseListOptions<chooseSection> options = new FirebaseListOptions.Builder<chooseSection>()
.setLayout(R.layout.section_list)
.setQuery(query,chooseSection.class)
.build();
adapter = new FirebaseListAdapter<chooseSection>(options) {
#Override
protected void populateView(#NonNull View view, #NonNull chooseSection model, int position) {
TextView sectionView = (TextView) view.findViewById(R.id.sectionView);
sectionView.setText(model.getSectionn());
chooseSection lu = sectionChosse;
//String LatLng = lu.getLocationUserLatitude() + "," + lu.getLocationUserLongitude();
//allItemsList.put(position, model.getSectionn());
}
};
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//String item = allItemsList.get(position);
Intent intent = new Intent(ChooseSectionActivity.this, PubsSectionActivity.class);
//intent.putExtra("key", item);
startActivity(intent);
}
});
listView.setAdapter(adapter);
}
#Override
protected void onStart() {
super.onStart();
adapter.startListening();
}
#Override
protected void onStop() {
super.onStop();
adapter.stopListening();
}
}
PubsSectionActivity.java
public class PubsSectionActivity extends AppCompatActivity {
ViewFlipper viewFlipp;
private DatabaseReference databaseReference;
private List<imageSection> slideLists;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pubs_section);
viewFlipp = findViewById(R.id.viewFlipper);
databaseReference = FirebaseDatabase.getInstance().getReference();
slideLists = new ArrayList<>();
}
#Override
protected void onStart() {
super.onStart();
usingFirebaseDatabase();
}
private void usingFirebaseDatabase() {
String lolipop = "Coiffeur";
databaseReference.child("Sections/Restaurant")
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
slideLists.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
imageSection model = snapshot.getValue(imageSection.class);
slideLists.add(model);
}
Toast.makeText(PubsSectionActivity.this, "All data fetched", Toast.LENGTH_SHORT).show();
usingFirebaseImages(slideLists);
} else {
Toast.makeText(PubsSectionActivity.this, "No images in firebase", Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(PubsSectionActivity.this, "NO images found \n" + databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
}
private void usingFirebaseImages(List<imageSection> slideLists) {
for (int i = 0; i < slideLists.size(); i++) {
String downloadImageUrl = slideLists.get(i).getImageUrl();
Toast.makeText(this, downloadImageUrl, Toast.LENGTH_LONG).show();
ImageView imageView = new ImageView(this);
Picasso.get().load(downloadImageUrl).fit().centerCrop().into(imageView);
viewFlipp.addView(imageView);
viewFlipp.setInAnimation(this, android.R.anim.slide_in_left);
viewFlipp.setOutAnimation(this, android.R.anim.slide_out_right);
}
}
}
Help me please, i'm stuck !!
i don't know why there is this error...

You're attaching a listener to Sections/Restaurant. Since that is one specific restaurant, you don't need to loop over the children in onDataChange.
So:
databaseReference.child("Sections/Restaurant")
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
slideLists.clear();
imageSection model = snapshot.getValue(imageSection.class);
slideLists.add(model);
Toast.makeText(PubsSectionActivity.this, "All data fetched", Toast.LENGTH_SHORT).show();
usingFirebaseImages(slideLists);
} else {
Toast.makeText(PubsSectionActivity.this, "No images in firebase", Toast.LENGTH_SHORT).show();
}
}

Delete items from listView Firebase

I have this problem when i open the view of "Eventos", im trying to delete from de database the selected items from the listview.
public class ShowData extends AppCompatActivity {
DatabaseReference databaseReference;
ListView listView;
ArrayList<String> arrayList = new ArrayList<>();
ArrayAdapter<String> arrayAdapter;
Button btnDelete;
Module module;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_data);
databaseReference = FirebaseDatabase.getInstance().getReference("Eventos");
listView = (ListView) findViewById(R.id.listViewShow);
btnDelete = (Button) findViewById(R.id.btnBorrarElemento);
module=((Module)getApplication());
arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList);
listView.setAdapter(arrayAdapter); .....
... listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> paramAdapterView, View view, int position, long id) {
module.setGvalue_titulo(arrayList.get(position));
module.setGvalue_descripcion(arrayList.get(position));
module.setGvalue_fecha(arrayList.get(position));
module.setGvalue_url(arrayList.get(position));
}
});
btnDelete.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
final String str = module.getGvalue_titulo().substring(0, 6);
if(str == ""){
Toast.makeText(ShowData.this, "No se ha seleccionado ningun elemento para eliminar", Toast.LENGTH_SHORT).show();
}
else {
databaseReference.child("Eventos").child(str).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
databaseReference.child(str).removeValue();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Toast.makeText(ShowData.this, "Evento Eliminado", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(getApplicationContext(),ShowData.class);
startActivity(intent);
}
}
}); ....
The module has the getters and setters necessaries:
In my manifest, I have this:

Your problem is that you are trying to cast your Application to Module, but it's not Module. Well, have you registered your Module as custom application implementation in your AndroidManifest.xml? If the answer is "no" than this is the exact reason! Follow this answer to check how to do it easily.

Can not get inside setOnItemSelectedListener from Spinner

Based on information from Android: Create spinner programmatically from array. I can select room choices from spinner based on ArrayList. However,it never get inside the process setOnItemSelectedListener.I cannot figure out why does it happen.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_room);
SpaceRoomTable = (TableLayout) findViewById(R.id.tvSpaceRoomTable);
AddroomButton = (Button)findViewById(R.id.btLinkAddRoom);
Backtomenu = (Button) findViewById(R.id.bBackToMenu_DogTrack);
Delete = ContextCompat.getDrawable(this, R.drawable.bin);
dropdown = (Spinner) findViewById(R.id.spinListRoom);
summitDelete = (Button) findViewById(R.id.btDeleteSummit);
AddroomButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent LinkToEditroom = new Intent (EditRoom.this,AddRoom.class);
startActivity(LinkToEditroom);
}
});
Backtomenu.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent LinkToHomeMenu = new Intent(EditRoom.this,HomeMenu.class);
EditRoom.this.startActivity(LinkToHomeMenu);
}
});
showRoom();
ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,showitemName);
spinnerArrayAdapter .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
dropdown.setAdapter(spinnerArrayAdapter);
dropdown.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
// Log.d("TEST","selection is ");
Object Itemselected = adapterView.getItemAtPosition(i);
Toast.makeText(getApplicationContext(),"Inside"+String.valueOf(Itemselected),Toast.LENGTH_SHORT).show();
}
#Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
}

In XML Layout :-
<Spinner
android:id="#+id/dropdown"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
then, in your activity findViewById like this:-
dropdown= (Spinner) findViewById(R.id.dropdown);
then Create an ArrayAdapter using the string array and a default spinner layout :-
ArrayAdapter<String> spinnerArrayAdapter = ArrayAdapter<String>(this, android.R.layout.simple_spinner_item,showitemName);
spinnerArrayAdapter .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
dropdown.setAdapter(spinnerArrayAdapter);
For OnIemClickListener use like this:-
public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener{
Spinner dropdown;
String[] showitemName = {"A","B","C","D","E"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dropdown= (Spinner) findViewById(R.id.dropdown);
dropdown.setOnItemSelectedListener(this);
ArrayAdapter<String> spinnerArrayAdapter = ArrayAdapter<String>(this, android.R.layout.simple_spinner_item,showitemName);
spinnerArrayAdapter .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
dropdown.setAdapter(spinnerArrayAdapter);
}
//Performing action onItemSelected and onNothing selected
#Override
public void onItemSelected(AdapterView<?> parent, View arg1, int position,long id) {
Toast.makeText(getApplicationContext(),"Inside" + parent.getItemAtPosition(position) , Toast.LENGTH_LONG).show();
}
#Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
More information:
You can check in details from these links:-
https://developer.android.com/guide/topics/ui/controls/spinner.html
https://developer.android.com/reference/android/widget/AdapterView.OnItemSelectedListener.html
https://android--code.blogspot.in/2015/08/android-spinner-onitemselected.html
http://www.java2s.com/Code/Android/UI/SpinnerItemSelectedListener.htm
https://android--code.blogspot.in/2015/08/android-spinner-get-selected-item-text.html

For more Information about showroom method
public void showRoom()
{
refroom.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(final DataSnapshot dataSnapshot) {
int Length_Record = dataSnapshot.child("CurrentUser").child("Tracking").child("ListRoom").child("LIST_ROOM_LENGTH").getValue(int.class);
int RunRecord =0;
int printRoom =0;
final String userId = dataSnapshot.child("CurrentUser").child("UserId").getValue(String.class);
for (DataSnapshot zonesnapshot : dataSnapshot.child("CurrentUser").child("Tracking").child("ListRoom").getChildren())
{
if(printRoom!=Length_Record)
{
zonesnapshot.getValue();
String[] parts = String.valueOf(zonesnapshot.getValue()).split(",");
String part1 = parts[0]; // Room Id
String part2 = parts[1]; // Room Name
String part3 = parts[2]; // TypeRoom
String OnRoom = dataSnapshot.child("CurrentUser").child("Tracking").child("Location").getValue(String.class);
itemsName.add(part2+","+part3); // put to arraylist to prepare a room choice for deletion
showitemName.add(part2+"("+part3+")");
itemOfUser.put(userId+"Room"+printRoom,part2+","+part3); // keep room for each user
inRow(dataSnapshot.child("CurrentUser").child("UserId").getValue(String.class), RunRecord, part2, OnRoom, part3);
}
printRoom++;
}
summitDelete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
storageReference = storage.getInstance().getReferenceFromUrl("gs://********-*****.appspot.com/imagesRoom").child(userId).child(selection);
storageReference.delete().addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
}
}).addOnFailureListener(new OnFailureListener() {
#Override
public void onFailure(#NonNull Exception e) {
Toast.makeText(getApplicationContext(),"Error Can not delete file",Toast.LENGTH_SHORT).show();
}
});
}
});
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

below code will get the selected item text automatically
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
// Log.d("TEST","selection is ");
String item = adapterView.getItemAtPosition(i).toString();
Toast.makeText(getApplicationContext(),"Inside"+item,Toast.LENGTH_SHORT).show();
}