When I try to get all the data from my database as a list, I get the following error from debugger and the code returns a null List.
public static DbOps get(Context ctx) {
if (sDbOps == null) {
sDbOps = new DbOps(ctx);
}
return sDbOps;
}
private DbOps(Context ctx) {
dbRef = FirebaseDatabase.getInstance().getReference().child("products");
if(mProducts == null) {
getProducts();
}
}
public List<Product> getProducts() {
dbRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> iterator = dataSnapshot.getChildren().iterator();
mProducts = new ArrayList<>();
while (iterator.hasNext()) {
Product pr = dataSnapshot.getValue(Product.class);
mProducts.add(pr);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return mProducts;
}
The error is because you are trying to access a variable that is not declared in the scope of that function.
To solve this, a simple solution is that, make the variable as private or public member of that class so that all member functions can access it.
Example
public class classname{
private FirebaseDatabase dbRef;
#Override
public void onStart(Intent intent, int startid) {
dbRef = FirebaseDatabase.getInstance().getReference().child("products");
}
//Or initialize in your own function
private DbOps(Context ctx) {
dbRef = FirebaseDatabase.getInstance().getReference().child("products");
if(mProducts == null) {
getProducts();
}
}
public List<Product> getProducts() {
dbRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> iterator = dataSnapshot.getChildren().iterator();
mProducts = new ArrayList<>();
while (iterator.hasNext()) {
Product pr = dataSnapshot.getValue(Product.class);
mProducts.add(pr);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return mProducts;
}
}
Related
I'm new to Android and I know this might be a piece of cake but I'm struggling.
I was trying to create a dynamic expandable recycler view using firebase realtime database but the data is not displaying properly.
I'm passing a string from one activity to another and comparing the string to the database field and then displaying it's child components but I don't know where I'm failing.
I want to display the Parent and child field by comparing the name field with the value.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_course_detail);
//string value from another activity
String value = getIntent().getExtras().getString("name");
recycler_view = (RecyclerView) findViewById(R.id.recycler_expand);
recycler_view.setLayoutManager(new LinearLayoutManager(this));
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference parentReference = database.getReference().child("Tutors");
//comparing
parentReference.equalTo(value).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
final List<ParentList> Parent = new ArrayList<>();
for (final DataSnapshot snapshot : dataSnapshot.getChildren()){
final String ParentKey = snapshot.getKey().toString();
snapshot.child("title").getValue();
DatabaseReference childReference =
FirebaseDatabase.getInstance().getReference().child(ParentKey);
childReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
final List<ChildList> Child = new ArrayList<>();
for (DataSnapshot snapshot1:dataSnapshot.getChildren())
{
final String ChildValue = snapshot1.getValue().toString();
snapshot1.child("title").getValue();
Child.add(new ChildList(ChildValue));
}
Parent.add(new ParentList(ParentKey, Child));
DocExpandableRecyclerAdapter adapter = new DocExpandableRecyclerAdapter(Parent);
recycler_view.setAdapter(adapter);
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
System.out.println("Failed to read value." + error.toException());
}
});}}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Database Structure
ChildList.java
public class ChildList implements Parcelable {
private String title;
public ChildList(String title) {
this.title = title;
}
protected ChildList(Parcel in) {
title = in.readString();
}
public static final Creator<ChildList> CREATOR = new Creator<ChildList>() {
#Override
public ChildList createFromParcel(Parcel in) {
return new ChildList(in);
}
#Override
public ChildList[] newArray(int size) {
return new ChildList[size];
}
};
public String getTitle() {
return title;
}
public void setTitle(String Title) {
this.title = Title;
}
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel parcel, int i) {
parcel.writeString(title);
}
}
Please anyone help me with this :(
Don't use equalTo().
Try this:
DatabaseReference parentReference = database.getReference().child("Tutors");
parentReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (final DataSnapshot snapshot : dataSnapshot.getChildren()){
final String NameKey = snapshot.getKey().toString();
if(value.equals(NameKey)){
//DO WHATEVER YOU WANT
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I am trying to show random users from Firebase Realtime Database .I am currently able to show one random user from my Firebase Realtime database but what i want to do is show 6 random users on to my recyclerview at once .But i am unable to figure out how to add query for same without getting an error at runtime.
Mycode
public class UsersFragment extends Fragment {
private RecyclerView recyclerView;
private UserAdapter mUserAdapter;
private List<User> mUsers;
String TAG = "MyTag";
ValueEventListener mValueEventListener;
List<String> UserIdsList = new ArrayList<>();
public UsersFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_users, container, false);
recyclerView = view.findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
mUsers = new ArrayList<>();
//readUser();
RandomUsers();
return view;
}
private void RandomUsers() {
//mUsers.add((User) UserIdsList);
mUserAdapter = new UserAdapter(getContext(), mUsers, false);
recyclerView.setAdapter(mUserAdapter);
mUserAdapter.notifyDataSetChanged();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference UserIdsRef = rootRef.child("UserIds");
ValueEventListener mValueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
String userIDS = ds.getKey();
UserIdsList.add(userIDS);
}
int UserListSize = UserIdsList.size();
Log.d(TAG, String.valueOf(UserListSize));
Random random=new Random();
int random1=random.nextInt(UserListSize);
// int Rdm= UserIdsList.get(new Random().nextInt(UserListSize));
DatabaseReference UserRef = rootRef.child("Users").child(UserIdsList.get(random1));
Log.d(TAG,"UserRef "+ String.valueOf(UserRef));
//new Random().nextInt(UserListSize)
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user = dataSnapshot.getValue(User.class);
mUsers.add(user);
mUserAdapter.notifyDataSetChanged();
String name = dataSnapshot.child("First").getValue(String.class);
Log.d(TAG, "Name called "+name);
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.d(TAG, "Error: " + databaseError.toException()); //Don't ignore errors!
}
};
UserRef.addListenerForSingleValueEvent(eventListener);
//UserRef.addValueEventListener(eventListener);
Query query2 = UserRef.limitToFirst(2);
query2.addListenerForSingleValueEvent(eventListener);
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.d(TAG, "Error: " + databaseError.getMessage()); //Don't ignore errors!
}
};
UserIdsRef.addListenerForSingleValueEvent(mValueEventListener);
//UserIdsRef.addValueEventListener(mValueEventListener);
}
}
UserAdapter.java
public class UserAdapter extends RecyclerView.Adapter<UserAdapter.ViewHolder> {
private Context mContext;
private List<User> mUsers;
private List<String> UserIdsList;
private boolean ischat;
String theLastMessage;
public UserAdapter(Context mContext, List<User> mUsers,boolean ischat) {
this.mContext = mContext;
this.mUsers = mUsers;
this.ischat=ischat;
}
#NonNull
#Override
public UserAdapter.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view= LayoutInflater.from(mContext).inflate(R.layout.user_item,parent,false);
return new UserAdapter.ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull UserAdapter.ViewHolder holder, int position) {
final User user=mUsers.get(position);
holder.username.setText(user.getFirst());
if (user.getImageURL().equals("default")){
holder.profile_image.setImageResource(R.mipmap.ic_launcher);
} else {
Glide.with(mContext).load(user.getImageURL()).into(holder.profile_image);
}
if (ischat){
lastMessage(user.getId(), holder.last_msg);
} else {
holder.last_msg.setVisibility(View.GONE);
}
if (ischat){
if (user.getStatus().equals("online")){
holder.img_on.setVisibility(View.VISIBLE);
holder.img_off.setVisibility(View.GONE);
} else {
holder.img_on.setVisibility(View.GONE);
holder.img_off.setVisibility(View.VISIBLE);
}
} else {
holder.img_on.setVisibility(View.GONE);
holder.img_off.setVisibility(View.GONE);
}
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(mContext, MessageActivity.class);
intent.putExtra("UserName",user.getFirst());
intent.putExtra("userid", user.getId());
intent.putExtra("ImageURL",user.getImageURL());
mContext.startActivity(intent);
}
});
}
#Override
public int getItemCount() {
return mUsers.size();
}
public class ViewHolder extends RecyclerView.ViewHolder{
public TextView username;
public ImageView profile_image;
private ImageView img_on;
private ImageView img_off;
private TextView last_msg;
public ViewHolder(#NonNull View itemView) {
super(itemView);
username=itemView.findViewById(R.id.username);
profile_image=itemView.findViewById(R.id.profile_image);
img_on = itemView.findViewById(R.id.img_on);
img_off = itemView.findViewById(R.id.img_off);
last_msg=itemView.findViewById(R.id.last_msg);
}
}
private void lastMessage(final String userid, final TextView last_msg){
theLastMessage = "default";
final FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Chats");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()){
Chat chat = snapshot.getValue(Chat.class);
if (firebaseUser != null && chat != null) {
if (chat.getReceiver().equals(firebaseUser.getUid()) && chat.getSender().equals(userid) ||
chat.getReceiver().equals(userid) && chat.getSender().equals(firebaseUser.getUid())) {
theLastMessage = chat.getMessage();
}
}
}
switch (theLastMessage){
case "default":
last_msg.setText("No Message");
break;
default:
last_msg.setText(theLastMessage);
break;
}
theLastMessage = "default";
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
}
Data Snapshot
DataSnapshot { key = KRhmaWXCctMHbU1Z6NAWRGGw2ag2, value = {EmailId=abc#gmail.com, First=shivam} }
You can try this:
DatabaseReference UserRef = rootRef.child("Users").orderByKey().startAt(UserIdsList.get(random1)).limitToFirst(6);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user = dataSnapshot.getValue(User.class);
mUsers.add(user);
mUserAdapter.notifyDataSetChanged();
String name = dataSnapshot.child("First").getValue(String.class);
Log.d(TAG, "Name called "+name);
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.d(TAG, "Error: " + databaseError.toException());
}
};
UserRef.addListenerForSingleValueEvent(eventListener);
So the problem is following - When mProducts is trying to get the products from the DB in onDataChange() call, then the fragment jumps to onCreateView(), sets the adapter with an empty array and after that performs the database task.
Am I missing something or what am I doing wrong?
Please point out the reason behind this weird behavior.
Thanks.
Fragment class
public class MainViewFragment extends Fragment {
private static final String TAG = "MainViewFragment";
private RecyclerView mView;
private List<Product> mProducts;
private DatabaseReference mRef;
private MainViewAdapter mAdapter;
public MainViewFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v = inflater.inflate(R.layout.fragment_main_view, container, false);
mView = (RecyclerView)v.findViewById(R.id.mainViewRecyclerView);
// mProducts = MockData.getProductData();
mView.setLayoutManager(new LinearLayoutManager(getActivity(),LinearLayoutManager.HORIZONTAL,false));
mAdapter = new MainViewAdapter(mProducts,getActivity());
mView.setAdapter(mAdapter);
return v;
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
mRef = FirebaseDatabase.getInstance().getReference().child("products");
mProducts = new ArrayList<>();
new Thread(new Runnable() {
#Override
public void run() {
mRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
mProducts = Db.getDatabase(getActivity(),mRef).getProducts();
}
#Override
public void onCancelled(DatabaseError databaseError) {}
});
}
}).start();
}
}
Database Class
public class Db {
private DatabaseReference mRef;
private Context ctx;
private static Db sDb;
private List<Product> mProduct;
public static Db getDatabase(Context ctx, DatabaseReference mRef) {
if(sDb == null) {
sDb = new Db(ctx,mRef);
}
return sDb;
}
private Db(Context ctx,DatabaseReference mRef) {
this.ctx = ctx;
this.mRef = mRef;
this.mRef = FirebaseDatabase.getInstance().getReference().child("products");
}
public List<Product> getProducts() {
mProduct = new ArrayList<>();
mRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterator<DataSnapshot> dataSnapshotIterator = dataSnapshot.getChildren().iterator();
Product product = null;
while (dataSnapshotIterator.hasNext()) {
DataSnapshot dataSnapshotChild = dataSnapshotIterator.next();
product = dataSnapshotChild.getValue(Product.class);
mProduct.add(product);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
});
return mProduct;
}
}
In your adapter class, you should have a setter method for your dataset:
public void setData (Dataset dataset) {
mDataset = dataset;
notifyDataSetChanged();
}
In the onAttach:
#Override
public void onAttach(Context context) {
super.onAttach(context);
mRef = FirebaseDatabase.getInstance().getReference().child("products");
mProducts = new ArrayList<>();
new Thread(new Runnable() {
#Override
public void run() {
mRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
mProducts = Db.getDatabase(getActivity(),mRef).getProducts();
mAdapter.setData(mProducts)
}
#Override
public void onCancelled(DatabaseError databaseError) {}
});
}
}).start();
It could be this line that has the problem
product = dataSnapshotChild.getValue(Product.class);
is not giving the desired result, in which case, I usually desiarialize this way:
Lets say the Product class has two components - name and price which are String and int respectively, I'd have done it this way, if I had a constructor in the Product class with both components as parameters
String name = dataSnapshotChild.child("name").getValue(String.class);
int price= dataSnapshotChild.child("price").getValue(Integer.class);
product = new Product(name, price);
mProduct.add(product);
where "name" and "price" are the node names in your database
I am trying to read the 'resName' and 'status' values from PjSxhQXCyXdSv07LxVzU7buvhkF2 under business_info node from firebase database, as seen .
I keep getting this error:
Attempt to invoke virtual method 'java.lang.String com.example.android.project_water.Utilities.RestaurantInformation.getResName()' on a null object reference.
Does anyone know how to solve this? Please let me know if more info is needed.
Code:
public class Info extends Fragment {
private DatabaseReference mDatabase;
private FirebaseAuth firebaseAuth;
private String businessID;
private TextView resNameChange, statusChange;
public Info() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_info, container, false);
SharedPreferences businessID1 = getActivity().getSharedPreferences("BUSINESS_ID", Context.MODE_PRIVATE);
businessID = businessID1.getString("businessID", "businessIDNotFound");
Log.i("BUSINESS KEY IS: ", businessID);
firebaseAuth = FirebaseAuth.getInstance();
mDatabase = FirebaseDatabase.getInstance().getReference();
resNameChange = rootView.findViewById(R.id.resNameChange);
statusChange = rootView.findViewById(R.id.statusChange);
mDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
showData(dataSnapshot);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return rootView;
}
public void showData(DataSnapshot dataSnapshot) {
if (dataSnapshot.child("business_info").child(businessID).exists()) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
RestaurantInformation resInfo = new RestaurantInformation();
//error on the line below******
resInfo.setResName(ds.child(businessID).getValue(RestaurantInformation.class).getResName());
resInfo.setStatus(ds.child(businessID).getValue(RestaurantInformation.class).getStatus());
resNameChange.setText(resInfo.getResName());
statusChange.setText(resInfo.getStatus());
}
} else {
resNameChange.setText("NAME");
statusChange.setText("ONLINE");
}
}
}
My Model
public class RestaurantInformation {
private String resName;
private String status;
public RestaurantInformation() {
}
public RestaurantInformation(String resName) {
this.resName = resName;
}
public RestaurantInformation(String resName, String status) {
this.resName = resName;
this.status = status;
}
public String getResName() {
return resName;
}
public void setResName(String resName) {
this.resName = resName;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
}
Your current code is downloading the entire database and then tries to figure out what to show client-side. That is a very wasteful use of your user's bandwidth. I recommend only listening for the business you're interested in:
mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("business_info").child(businessID).addValueEventListener(new ValueEventListener() {
Then you can simplify your showData method to:
public void showData(DataSnapshot snapshot) {
if (snapshot.exists()) {
RestaurantInformation resInfo = snapshot.getValue(RestaurantInformation.class)
resNameChange.setText(resInfo.getResName());
statusChange.setText(resInfo.getStatus());
} else {
resNameChange.setText("NAME");
statusChange.setText("ONLINE");
}
}
I'm trying to update and delete data in Firebase database.
SectionDetails model
public class SectionDetails {
private String sectionCode;
private String sectionSeats;
private String sectionKey;
public SectionDetails() {
}
public SectionDetails(String sectionCode, String sectionSeats) {
this.sectionCode = sectionCode;
this.sectionSeats = sectionSeats;
}
#Exclude
public String getSectionKey() {
return sectionKey;
}
public String getSectionCode() {
return sectionCode;
}
public String getSectionSeats() {
return sectionSeats;
}
}
FirebaseHelper class
public class FirebaseHelper {
DatabaseReference db;
ArrayList<SectionDetails> sectionDetailsArrayList = new ArrayList<>();
public FirebaseHelper(DatabaseReference db) {
this.db = db;
}
private void fetchData(DataSnapshot dataSnapshot) {
SectionDetails sectionDetails = dataSnapshot.getValue(SectionDetails.class);
sectionDetailsArrayList.add(sectionDetails);
adapter.notifyDataSetChanged();
}
public ArrayList<SectionDetails> retrieve() {
db.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
fetchData(dataSnapshot);
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
fetchData(dataSnapshot);
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
adapter.notifyDataSetChanged();
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return sectionDetailsArrayList;
}
}
CustomAdapter class
public class CustomAdapter extends BaseAdapter {
DatabaseReference updateRef;
String key;
Context c;
ArrayList<SectionDetails> sectionDetailsArrayList;
public CustomAdapter(Context c, ArrayList<SectionDetails> sectionDetailsArrayList) {
this.c = c;
this.sectionDetailsArrayList = sectionDetailsArrayList;
}
#Override
public int getCount() {
return sectionDetailsArrayList.size();
}
#Override
public Object getItem(int position) {
return sectionDetailsArrayList.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
final SectionDetails sd = (SectionDetails) this.getItem(position);
updateRef = FirebaseDatabase.getInstance().getReference().child(Constants.FIREBASE_COURSES).child("sections");
convertView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final Dialog d = new Dialog(CustomAdapter.this);
d.setContentView(R.layout.section_custom_dialog);
Button btnUpdate = (Button) d.findViewById(R.id.btnUpdate);
Button btnDelete = (Button) d.findViewById(R.id.btnDelete);
btnUpdate.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final String code = "1B";
final String seats = "20";
updateRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
SectionDetails updateSD = snapshot.getValue(SectionDetails.class);
if (sd.getSectionCode().equals(updateSD.getSectionCode())) {
key = snapshot.getKey().toString();
}
}
SectionDetails newSD = new SectionDetails(code, seats);
updateRef.child(key).setValue(newSD);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
btnDelete.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
updateRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
SectionDetails deleteSD = snapshot.getValue(SectionDetails.class);
if (sd.getSectionCode().equals(deleteSD.getSectionCode())) {
updateSectionRef.child(snapshot.getKey().toString()).removeValue();
break;
}
}
adapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
d.show();
}
});
return convertView;
}
}
MainActivity class
public class MainActivity extends AppCompatActivity {
DatabaseReference mRef;
FirebaseHelper helper;
CustomAdapter adapter;
ListView lvSectionsListOne;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lvSectionsListOne = (ListView) findViewById(R.id.lvSectionsList);
mRef = FirebaseDatabase.getInstance().getReference().child(Constants.FIREBASE_COURSES).child("sections");
helper = new FirebaseHelper(mRef);
adapter = new CustomAdapter(this, helper.retrieve());
lvSectionsListOne.setAdapter(adapter);
}
}
The data is deleted from database as expected, but the data that gets deleted remains inside the listview. I added adapter.notifyDataSetChanged() but still the listview is not updating.
The data is also updated as expected, but when update button is clicked, the data is updated infinitely. I can see the listview as well as the database keep on appending the data, and can only be stopped by closing the app.
I have tried to move SectionDetails newSD = new SectionDetails(code, seats) and updateRef.child(key).setValue(newSD) to outside for loop but the data doesn't get updated because the key is not passed to the path outside the for loop.
I haven't thoroughly looked at all the code you posted and may not understand your processing completely. There are two things that might be causing some of the problems you described.
In FirebaseHelper, method onChildChanged() calls fetchData(), which adds the changed section details to the array list. Shouldn't you be updating the existing section details instead of adding them again? Also, in onChildRemoved(), the section details are not removed from the array list. Don't they need to be removed?
In CustomAdapter the click listeners for your buttons add anonymous ValueEventListeners. Because they are anonymous, you have no way of removing them when they are no longer needed. ValueEventListeners added with addValueEventListener() remain active until removed. If your goal is to get the data once, use addListenerForSingleValueEvent().