How to get all nested child's data in Firebase database? - android

I have a Firebase database structure below. How do I get the value of room_name_public? I want to retrieve all those values and show it in a list view. Here, 55aqdTkLPrMwB6H0KX4Z0RUe6s52 is a Firebase userID and -KcqR5Db5BidD0XpQ1z1 is created by the push() function.


Ok, you can try in this way.
Create a plain object, like this:
public class Room {
String room_name_pucblic;
public Room() {
}
public Room(String room_name_pucblic) {
this.room_name_pucblic = room_name_pucblic;
}
public String getRoom_name_pucblic() {
return room_name_pucblic;
}
#Exclude
public Map<String, Object> toMap() {
HashMap<String, Object> result = new HashMap<>();
result.put("room_name_pucblic", room_name_pucblic);
return result;
}
}
Next, in your activity or fragment, declare and define the listener:
ValueEventListener roomsValueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for ( DataSnapshot userDataSnapshot : dataSnapshot.getChildren() ) {
if (userDataSnapshot != null) {
for ( DataSnapshot roomDataSnapshot : userDataSnapshot.getChildren() ) {
Room room = roomDataSnapshot.getValue(Room.class);
yourList.add(room.getRoom_name_pucblic());
yourAdapter.notifyDataSetChanged();
}
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
mFirebaseDatabaseReference.addListenerForSingleValueEvent(roomsValueEventListener);
I suppose that mFirebaseDatabaseReference is the firebase reference of your public_rooms node. yourList is an ArrayList of strings, connected to your adapter for the list view.
Hope this helps
Update
If you want to fetch user's rooms, knowing an userId, you have to edit the previous approach in this way:
ValueEventListener roomsValueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for ( DataSnapshot roomDataSnapshot : dataSnapshot.getChildren() ) {
Room room = roomDataSnapshot.getValue(Room.class);
yourList.add(room.getRoom_name_pucblic());
yourAdapter.notifyDataSetChanged();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
mFirebaseDatabaseReference = FirebaseDatabase.getInstance().getReference();
mFirebaseDatabaseReference.child(userId).addListenerForSingleValueEvent(roomsValueEventListener);

Related

I am getting ConcurrentModificationException while creating a chat application

While displaying the recent chats fragment in the application I am fetching my chats from firebase and filtering out the chats by their receiverID and senderID in the chat object to display the recent chats.
The problem says ConcurrentModificationException in ArrayList and it looks like due to the complexity of searching id in the array it occurred, I need a solution to minimize this chat filteration complexity.
// private List<String> stringList; Declaration at top
stringList = new ArrayList<>();
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
databaseReference = FirebaseDatabase.getInstance().getReference("BaatCheet/Chats/");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
//userModelList.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
MessageModel messageModel = dataSnapshot1.getValue(MessageModel.class);
if (messageModel.getSender().equals(firebaseUser.getUid())){
stringList.add(messageModel.getReceiver());
}
if (messageModel.getReceiver().equals(firebaseUser.getUid())){
stringList.add(messageModel.getSender());
}
}
readChat();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
The read chat function
private void readChat() {
userModelList = new ArrayList<>();
databaseReference = FirebaseDatabase.getInstance().getReference("BaatCheet/Users/");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
userModelList.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
UserModel userModel = dataSnapshot1.getValue(UserModel.class);
for (String id: stringList){
if (userModel.getId().equals(id)){
if (userModelList.size() !=0){
for (UserModel userModel1 : userModelList){
if (!userModel.getId().equals(userModel1.getId())){
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // If the existing list don't have same value for sender and reciever
} // end of inner userModel
} else {
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // end of else
} // end of userModel id equals string id
} // end of String is loop
} // end of DataSnapshot loop
usersAdapter = new UsersAdapter(userModelList);
recyclerView.setAdapter(usersAdapter);
} // end of onDataChange
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}// end of readChat()
The results would be the recyclerView of recent chats containing the chats which contain messages either send by the sender or receiver to each other.

In the following snippet of code :
for (UserModel userModel1 : userModelList){
if (!userModel.getId().equals(userModel1.getId())){
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // If the existing list don't have same value for sender and reciever
} //
You are modifying userModelList while iterating through userModelList. This is not allowed and is the cause of ConcurrentModificationException.
There are few ways to simplify the logic, the simplest (albeit not the best) would be to convert this foreach loop into a simple for i loop.
for (int i = 0; i< userModelList.size(); i++) {
UserModel userModel1 = userModelList.get(i);
if (!userModel.getId().equals(userModel1.getId())){
userModelList.add(userModel);
Log.d("DataAdded",userModel.getId());
} // If the existing list don't have same value for sender and reciever
} //

Basically to handle this complexity I am now using separate nodes just for storing the chatLists as such now I don't need to read chats for filtering the recent chats.
The below code is for creating a new node everytime user sends a message it will update the node if the recieverID is different.
dbrefChatList = FirebaseDatabase.getInstance().
getReference("BaatCheet/ChatList/")
.child(senderuserID)
.child(receiveruserID);
dbrefChatList.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (!dataSnapshot.exists()){
dbrefChatList.child("id").setValue(receiveruserID);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
As such ChatList is a Model Class which contains single String called "id" and this id will be used to search in the node.
The below code is for the ChatFragment which fetches the chatList from firebase and set the data to recycler view.
// private List<ChatList> chatList; Declaration at top
chatListList = new ArrayList<>();
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
databaseReference = FirebaseDatabase
.getInstance()
.getReference("BaatCheet/ChatList")
.child(firebaseUser.getUid());
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
chatListList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()){
ChatList chatList = snapshot.getValue(ChatList.class);
chatListList.add(chatList);
}
myChatList();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
The function myChatList act as the function of readChat in the problem statement.
private void myChatList() {
userModelList = new ArrayList<>();
databaseReference = FirebaseDatabase.getInstance().getReference("BaatCheet/Users/");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
userModelList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()){
UserModel userModel = snapshot.getValue(UserModel.class);
for (ChatList chatList : chatListList){
if (userModel.getId().equals(chatList.getId())){
userModelList.add(userModel);
}
}
}
usersAdapter = new UsersAdapter(userModelList);
recyclerView.setAdapter(usersAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}

You can set a flag while traversing the array, after it's done, add it if it doesn't exist yet:
// Display 1 user from chats
for (String id : str_usersList) {
if (user.getId().equals(id)) {
if (userList.size() != 0) {
boolean exists = false;
// If not exists then add
for (User user1 : userList) {
if (user.getId().equals(user1.getId())) {
exists = true;
}
}
if (!exists) {
userList.add(user);
}
} else {
userList.add(user);
}
}
}

Can't convert object of type java.lang.String to type

I have a problem after I add another table to my firebase database. it gives me following error:
com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type ...
here is my code, which works fine if I have database like this:
and code:
Main activity code:
rvOrder = (RecyclerView) findViewById(R.id.rvOrders);
rvOrder.setLayoutManager(new LinearLayoutManager(this));
databaseReference= FirebaseDatabase.getInstance().getReference();
firebaseHelper=new FirebaseHelper(databaseReference);
myAdapter=new MyAdapter(this,firebaseHelper.retrieve());
rvOrder.setAdapter(myAdapter);
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
rvOrder.setAdapter(myAdapter);
myAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Firebase helper code:
public class FirebaseHelper {
DatabaseReference databaseReference ;
Boolean saved = null;
ArrayList<Order> orders = new ArrayList<>();
public FirebaseHelper(DatabaseReference databaseReference) {
this.databaseReference = databaseReference;
}
public Boolean save(Order order) {
if (order == null) {
saved = false;
} else {
try {
databaseReference.child("Orders").push().setValue(order);
saved = true;
} catch (DatabaseException e) {
e.printStackTrace();
saved = false;
}
}
return saved;
}
private void fetchData(DataSnapshot dataSnapshot) {
orders.clear();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
System.out.println(ds.getValue(Order.class));
Order order = ds.getValue(Order.class);
orders.add(order);
}
}
public ArrayList<Order> retrieve() {
databaseReference.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) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return orders;
}
If I change my code to this (which I saw in this question link to the question ):
in Main activity:
databaseReference= FirebaseDatabase.getInstance().getReference();
to
databaseReference= FirebaseDatabase.getInstance().getReference().child("Orders");
and in firebasehelper:
for(DataSnapshot ds : dataSnapshot.getChildren()) {
System.out.println(ds.getValue(Order.class));
Order order = ds.getValue(Order.class);
orders.add(order);
}
to
System.out.println(dataSnapshot.getValue(Order.class));
Order order = dataSnapshot.getValue(Order.class);
orders.add(order);
then I am able to add another tables to database but I just get only the last item from the Orders table.
I want to add many tables with multiple items into the database and also I want to get all items from the "Orders" table.
Can anybody suggest me anything?

In your first code snippet you read from the root of the database. Since you're trying to read orders, you should read from /Orders instead:
databaseReference= FirebaseDatabase.getInstance().getReference();
firebaseHelper=new FirebaseHelper(databaseReference);
//myAdapter=new MyAdapter(this,firebaseHelper.retrieve());
//rvOrder.setAdapter(myAdapter);
databaseReference.child("Orders").addValueEventListener(new ValueEventListener() {
Now in your onDataChange you can read the orders by looping over them. Since you already do precisely that in FirebaseHelper.fetchData, you can call that method:
public void onDataChange(DataSnapshot dataSnapshot) {
firebaseHelper.fetchData(dataSnapshot);
}
Now all that is left is to wire up the data from firebaseHelper.orders to an adapter and the view:
public void onDataChange(DataSnapshot dataSnapshot) {
firebaseHelper.fetchData(dataSnapshot);
myAdapter=new MyAdapter(this,firebaseHelper.orders);
rvOrder.setAdapter(myAdapter);
}
This last step will require that you make FirebaseHelper.orders public, and probably some of the variables must be final.

I think you need to update this method accordingly:
public Boolean save(Order order) {
if (order == null) {
saved = false;
} else {
try {
databaseReference.child("Orders").push().setValue(order);
saved = true;
} catch (DatabaseException e) {
e.printStackTrace();
saved = false;
}
}
return saved;
}
Try to change:
databaseReference.child("Orders").push().setValue(order);
To:
databaseReference.child("Orders").child(order.getId).setValue(order);
Also, to retreive all Orders keep using the enhanced loop:
for(DataSnapshot ds : dataSnapshot.getChildren()) {
System.out.println(ds.getValue(Order.class));
Order order = ds.getValue(Order.class);
orders.add(order);
}

Update Multiple Firebase nodes

I need to update few nodes in firebase data which is posted from the server end.Need to update the node "is_done" to 0/1 from the device end.I have tried with different solutions but all became futile i.e it is adding a different node outside the "schedule" node.
Code snippet I have tried
private void updatemultiplefirebasedata() {
FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
final DatabaseReference reference = firebaseDatabase.getReference();
Query query = reference.child("schedule").child("22-12-2017").child("route").child("1").child("kid").child("21");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for(DataSnapshot d : dataSnapshot.getChildren()) {
Log.d("Keys",String.valueOf(d.getKey())); //returning all the keys
HashMap<String, Object> result = new HashMap<>();
result.put("is_done", "0");
reference.child(String.valueOf(d.getKey())).updateChildren(result); //update according to keys
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

That's because your database reference still points to the root of your tree. You should assign the desired path to that reference.
Also: You don't need Queries in order to access data directly. You can simply attach a listener to the Database Reference.
private void updatemultiplefirebasedata() {
FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
final DatabaseReference reference = firebaseDatabase.getReference().child("schedule").child("22-12-2017").child("route").child("1").child("kid").child("21");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for(DataSnapshot d : dataSnapshot.getChildren()) {
Log.d("Keys",String.valueOf(d.getKey())); //returning all the keys
HashMap<String, Object> result = new HashMap<>();
result.put("is_done", "0");
reference.child(String.valueOf(d.getKey())).updateChildren(result); //update according to keys
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

Try this :
reference.child(d.getKey()).updateChildren(result);
remove String.valueOf from child because your key is integer and you are passing it as string so instead of pointing it to same child it will create new key with String "1"

Cannot read list from Firebase, Map expected [duplicate]

I want to convert all Firebase DataSnapshot children to a list in android.
Something like this:
mFirebaseRef = new Firebase(FIREBASE_URL);
mFirebaseRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> td = (ArrayList<String>) dataSnapshot.getValue();
//notifyDataSetChanged();
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});

I hope below code works
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Log.e("Count " ,""+snapshot.getChildrenCount());
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
<YourClass> post = postSnapshot.getValue(<YourClass>.class);
Log.e("Get Data", post.<YourMethod>());
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.e("The read failed: " ,firebaseError.getMessage());
}
});

Firebase stores a sequence of values in this format:
"-K-Y_Rhyxy9kfzIWw7Jq": "Value 1"
"-K-Y_RqDV_zbNLPJYnOA": "Value 2"
"-K-Y_SBoKvx6gAabUPDK": "Value 3"
If that is how you have them, you are getting the wrong type. The above structure is represented as a Map, not as a List:
mFirebaseRef = new Firebase(FIREBASE_URL);
mFirebaseRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> td = (HashMap<String,Object>) dataSnapshot.getValue();
List<Object> values = td.values();
//notifyDataSetChanged();
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});

FirebaseDatabase mFirebaseDatabase = FirebaseDatabase.getInstance();
DatabaseReference databaseReference = mFirebaseDatabase.getReference(FIREBASE_URL);
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
Log.v(TAG,""+ childDataSnapshot.getKey()); //displays the key for the node
Log.v(TAG,""+ childDataSnapshot.child(--ENTER THE KEY NAME eg. firstname or email etc.--).getValue()); //gives the value for given keyname
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Hope it helps!

as Frank said Firebase stores sequence of values in the format of "key": "Value"
which is a Map structure
to get List from this sequence you have to
initialize GenericTypeIndicator with HashMap of String and your Object.
get value of DataSnapShot as GenericTypeIndicator into Map.
initialize ArrayList with HashMap values.
GenericTypeIndicator<HashMap<String, Object>> objectsGTypeInd = new GenericTypeIndicator<HashMap<String, Object>>() {};
Map<String, Object> objectHashMap = dataSnapShot.getValue(objectsGTypeInd);
ArrayList<Object> objectArrayList = new ArrayList<Object>(objectHashMap.values());
Works fine for me, Hope it helps.

I did something like this :
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Map<String, Object> objectMap = (HashMap<String, Object>)
dataSnapshot.getValue();
List<Match> = new ArrayList<Match>();
for (Object obj : objectMap.values()) {
if (obj instanceof Map) {
Map<String, Object> mapObj = (Map<String, Object>) obj;
Match match = new Match();
match.setSport((String) mapObj.get(Constants.SPORT));
match.setPlayingWith((String) mapObj.get(Constants.PLAYER));
list.add(match);
}
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});

In my case only given solution worked fine.
Screenshot of Firebase ArrayList structure:
How to fetch whole list from Firebase from DataSnapshot.
GenericTypeIndicator<Map<String, List<Education>>> genericTypeIndicator = new GenericTypeIndicator<Map<String, List<Education>>>() {};
Map<String, List<Education>> hashMap = dataSnapshot.getValue(genericTypeIndicator);
for (Map.Entry<String,List<Education>> entry : hashMap.entrySet()) {
List<Education> educations = entry.getValue();
for (Education education: educations){
Log.i(TAG, education.Degree);
}
}
Education.java: (Model class).
public class Education implements Serializable{
public String Degree;
public String Result;
}
Hope this would works fine.

#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
User user = postSnapshot.getValue(User.class);
list.add(user);
}
for (int i=0;i<list.size();i++)
{
Log.e("Name",list.get(i).getname());
Log.e("Phone",list.get(i).getphone());
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.e("error",firebaseError.getMessage());
}
});
Class model
class User{
String name;
String phone;
public String getname() {
return name;
}
public void setname(String name) {
this.name = name;
}
public String getphone() {
return phone;
}
public void setphone(String phone) {
this.phone = phone;
}
}
List binding
List<User> list= new ArrayList <>();
this work for you

If you use Kotlin, the next one is a good solution:
myRef.addListenerForSingleValueEvent(object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
val list = dataSnapshot.children.map { it.getValue(YourClass::class.java)!! }
Log.d("TAG", "Value is: $list")
}

Saving and Retriving data to - from Firebase ( deprecated ver 2.4.2 )
Firebase fb_parent = new Firebase("YOUR-FIREBASE-URL/");
Firebase fb_to_read = fb_parent.child("students/names");
Firebase fb_put_child = fb_to_read.push(); // REMEMBER THIS FOR PUSH METHOD
//INSERT DATA TO STUDENT - NAMES I Use Push Method
fb_put_child.setValue("Zacharia"); //OR fb_put_child.setValue(YOUR MODEL)
fb_put_child.setValue("Joseph"); //OR fb_put_child.setValue(YOUR MODEL)
fb_put_child.setValue("bla blaaa"); //OR fb_put_child.setValue(YOUR MODEL)
//GET DATA FROM FIREBASE INTO ARRAYLIST
fb_to_read.addValuesEventListener....{
public void onDataChange(DataSnapshot result){
List<String> lst = new ArrayList<String>(); // Result will be holded Here
for(DataSnapshot dsp : result.getChildren()){
lst.add(String.valueOf(dsp.getKey())); //add result into array list
}
//NOW YOU HAVE ARRAYLIST WHICH HOLD RESULTS
for(String data:lst){
Toast.make(context,data,Toast.LONG_LENGTH).show;
}
}
}

mDatabase.child("token").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot:dataSnapshot.getChildren())
{
String key= snapshot.getKey();
String value=snapshot.getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(ListUser.this,databaseError.toString(),Toast.LENGTH_SHORT).show();
}
});
Only work If child have no SubChild

Works Like a Charm
final DatabaseReference senderDb = FirebaseDatabase.getInstance().getReference(Constant.NODE_MESSAGE).child(myId + "_" + otherId);
senderDb.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> td = (HashMap<String,Object>) dataSnapshot.getValue();
for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
DatabaseReference objRef = senderDb.child( childDataSnapshot.getKey());
Map<String,Object> taskMap = new HashMap<String,Object>();
taskMap.put("is_read", "1");
objRef.updateChildren(taskMap); //should I use setValue()...?
Log.v("Testing",""+ childDataSnapshot.getKey()); //displays the key for the node
}
//notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

You Need to write a custom Deserializer and then loop it and get the values of the hasmap.
Custom Deserializer:-
public class UserDetailsDeserializer implements JsonDeserializer<AllUserDetailsKeyModel> {
/*
bebebejunskjd:{
"email": "akhilbv1#gmail.com",
"mobileNum": "12345678",
"password": "1234567",
"username": "akhil"}*/
#Override public AllUserDetailsKeyModel deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
final JsonObject jsonObject = json.getAsJsonObject();
Gson gson = new Gson();
Type AllUserDetailsResponseModel =
new TypeToken<HashMap<String, AllUserDetailsResponseModel>>(){}.getType();
HashMap<String, AllUserDetailsResponseModel> user =
gson.fromJson(jsonObject, AllUserDetailsResponseModel);
AllUserDetailsKeyModel result = new AllUserDetailsKeyModel();
result.setResult(user);
return result;
}
}
The code in comments is my object model and u should replaceAllUserDetailsKeyModel with your model class and add this to the rest client like below:-
private Converter.Factory createGsonConverter() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(AllUserDetailsKeyModel.class, new UserDetailsDeserializer());
Gson gson = gsonBuilder.create();
return GsonConverterFactory.create(gson);
}
This the custom Convertor for Retrofit.
In your onResponse you just loop with hasmaps and get value by key and my model class looks like below:-
public class AllUserDetailsKeyModel {
private Map<String, AllUserDetailsResponseModel> result;
public Map<String, AllUserDetailsResponseModel> getResult() {
return result;
}
public void setResult(Map<String, AllUserDetailsResponseModel> result) {
this.result = result;
}
}
probably you need to give a Type T where T is your data Type and my model consists only of a hashmap and getters and setters for that.
And finally set Custom Convertor to retrofit like below:- .addConverterFactory(createGsonConverter())
Let me know if you need more clarifications.

Use GenericTypeIndicator to get List of Child Node from Firebase ArrayList structured DataBase
//Start of Code
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener(){
#Override
public void onDataChange(DataSnapshot snapshot){
GenericTypeIndicator<List<YourClassName>> t = new GenericTypeIndicator<List<YourClassName>>{};
List<YourClassName> messages = snapshot.getValue(t);
Log.d("Get Data Size", messages.size());
}
}
#Override
public void onCancelled(FirebaseError firebaseError){
Log.e("The read failed: ",firebaseError.getMessage());
}
});

your problem is why your code doesn't work.
this your code:
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Log.e("Count " ,""+snapshot.getChildrenCount());
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
<YourClass> post = postSnapshot.getValue(<YourClass>.class);
Log.e("Get Data", post.<YourMethod>());
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.e("The read failed: " ,firebaseError.getMessage());
}
})
you miss the simplest thing: getChildren()
FirebaseDatabase db = FirebaseDatabase.getInstance();
DatabaseReference reference = FirebaseAuth.getInstance().getReference("Donald Trump");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int count = (int) dataSnapshot.getChildrenCount(); // retrieve number of childrens under Donald Trump
String[] hairColors = new String[count];
index = 0;
for (DataSnapshot datas : dataSnapshot.getChildren()){
hairColors[index] = datas.getValue(String.class);
}
index ++
for (int i = 0; i < count; i++)
Toast(MainActivity.this, "hairColors : " + hairColors[i], toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

ArrayList<String> keyList = new ArrayList<String>();
mKeyRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
String temp = childDataSnapshot.getKey();
keyList.add(temp);
i = keyList.size();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
This code is working fine to add all firebase key into arraylist, you can do it with firebase values, of other static values.

DatabaseReference mRootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference mMainMenuRef = mRootRef.child("tut_master");//main
DatabaseReference mSubMenuRef = mMainMenuRef.child("english");//sub
List<Tutorial> tutorialNames=new ArrayList<>();
mSubMenuRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
long id = ds.child("id").getValue(Long.class);
String name = ds.child("name").getValue(String.class);
Tutorial tut = new Tutorial();
tut.setTutId(id+"");
tut.setTutName(name);
tutList.add(tut);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

private FirebaseDatabase firebaseDatabase= FirebaseDatabase.getInstance();
private DatabaseReference databaseReference= firebaseDatabase.getReference();
private DatabaseReference mChildReference= databaseReference.child("data");
mChildReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
User commandObject = ds.getValue(User.class);
Log.d("TAG", commandObject.getMsg());
}
Toast.makeText(MainActivity.this,dataSnapshot.toString(),Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
This will help you, you just have to create a model class containing String msg.

Use Gson is my favorite solution.
mFirebaseRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Type StringListType = new TypeToken<List<String>>(){}.getType();
List<String> td = new Gson().fromJson(dataSnapshot.getValue(), StringListType);
}
});
if you think the code to get TypeToken is unintuitive. You can write a class to contain all types you need. So next time, you can get those types quickly.
class TypeTokens{
static public final Type StringListType = new TypeToken<List<String>>(){}.getType();
static public final Type StringMapType = new TypeToken<Map<String, String>>(){}.getType();
static public final Type LongMapType = new TypeToken<Map<String, Long>>(){}.getType();
static public final Type DateMapType = new TypeToken<Map<String, Date>>(){}.getType();
}

Here goes my 2 cents contribution (in Kotlin):
private fun getData(childUid:String) {
refDB = firebaseDB.reference.child(MAIN_DATABASE_FOLDER).child(childUid)
if(childEventDataListener == null) {
childEventDataListener = object : ChildEventListener {
override fun onChildAdded(snapshot: DataSnapshot, previousChildName: String?) {
for(snap in snapshot.children) {
val newParcel = snapshot.getValue(YourClassConverter::class.java)!!
}
}
override fun onChildChanged(snapshot: DataSnapshot, previousChildName: String?) { }
override fun onChildRemoved(snapshot: DataSnapshot) { }
override fun onChildMoved(snapshot: DataSnapshot, previousChildName: String?) {}
override fun onCancelled(error: DatabaseError) {}
}
refDB.addChildEventListener(childEventDataListener!!)
}
}
The class YourClassConverter shall follow this rule as noted in the getValue header's comment shown below. I prefer to use this converter since I can control the default values passed when some of them are not defined in the firebase.
This method is used to marshall the data contained in this snapshot into a class of your choosing. The class must fit 2 simple constraints:
The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized
An example class might look like:
class Message {
private String author;
private String text;
private Message() {}
public Message(String author, String text) {
this.author = author;
this.text = text;
}
public String getAuthor() {
return author;
}
public String getText() {
return text;
}
}
// Later
Message m = snapshot.getValue(Message.class);

How to extract a list of objects from Firebase DataSnapshot on android

I want to convert all Firebase DataSnapshot children to a list in android.
Something like this:
mFirebaseRef = new Firebase(FIREBASE_URL);
mFirebaseRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> td = (ArrayList<String>) dataSnapshot.getValue();
//notifyDataSetChanged();
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});

I hope below code works
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Log.e("Count " ,""+snapshot.getChildrenCount());
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
<YourClass> post = postSnapshot.getValue(<YourClass>.class);
Log.e("Get Data", post.<YourMethod>());
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.e("The read failed: " ,firebaseError.getMessage());
}
});

Firebase stores a sequence of values in this format:
"-K-Y_Rhyxy9kfzIWw7Jq": "Value 1"
"-K-Y_RqDV_zbNLPJYnOA": "Value 2"
"-K-Y_SBoKvx6gAabUPDK": "Value 3"
If that is how you have them, you are getting the wrong type. The above structure is represented as a Map, not as a List:
mFirebaseRef = new Firebase(FIREBASE_URL);
mFirebaseRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> td = (HashMap<String,Object>) dataSnapshot.getValue();
List<Object> values = td.values();
//notifyDataSetChanged();
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});

FirebaseDatabase mFirebaseDatabase = FirebaseDatabase.getInstance();
DatabaseReference databaseReference = mFirebaseDatabase.getReference(FIREBASE_URL);
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
Log.v(TAG,""+ childDataSnapshot.getKey()); //displays the key for the node
Log.v(TAG,""+ childDataSnapshot.child(--ENTER THE KEY NAME eg. firstname or email etc.--).getValue()); //gives the value for given keyname
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Hope it helps!

as Frank said Firebase stores sequence of values in the format of "key": "Value"
which is a Map structure
to get List from this sequence you have to
initialize GenericTypeIndicator with HashMap of String and your Object.
get value of DataSnapShot as GenericTypeIndicator into Map.
initialize ArrayList with HashMap values.
GenericTypeIndicator<HashMap<String, Object>> objectsGTypeInd = new GenericTypeIndicator<HashMap<String, Object>>() {};
Map<String, Object> objectHashMap = dataSnapShot.getValue(objectsGTypeInd);
ArrayList<Object> objectArrayList = new ArrayList<Object>(objectHashMap.values());
Works fine for me, Hope it helps.

I did something like this :
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Map<String, Object> objectMap = (HashMap<String, Object>)
dataSnapshot.getValue();
List<Match> = new ArrayList<Match>();
for (Object obj : objectMap.values()) {
if (obj instanceof Map) {
Map<String, Object> mapObj = (Map<String, Object>) obj;
Match match = new Match();
match.setSport((String) mapObj.get(Constants.SPORT));
match.setPlayingWith((String) mapObj.get(Constants.PLAYER));
list.add(match);
}
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});

In my case only given solution worked fine.
Screenshot of Firebase ArrayList structure:
How to fetch whole list from Firebase from DataSnapshot.
GenericTypeIndicator<Map<String, List<Education>>> genericTypeIndicator = new GenericTypeIndicator<Map<String, List<Education>>>() {};
Map<String, List<Education>> hashMap = dataSnapshot.getValue(genericTypeIndicator);
for (Map.Entry<String,List<Education>> entry : hashMap.entrySet()) {
List<Education> educations = entry.getValue();
for (Education education: educations){
Log.i(TAG, education.Degree);
}
}
Education.java: (Model class).
public class Education implements Serializable{
public String Degree;
public String Result;
}
Hope this would works fine.

#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
User user = postSnapshot.getValue(User.class);
list.add(user);
}
for (int i=0;i<list.size();i++)
{
Log.e("Name",list.get(i).getname());
Log.e("Phone",list.get(i).getphone());
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.e("error",firebaseError.getMessage());
}
});
Class model
class User{
String name;
String phone;
public String getname() {
return name;
}
public void setname(String name) {
this.name = name;
}
public String getphone() {
return phone;
}
public void setphone(String phone) {
this.phone = phone;
}
}
List binding
List<User> list= new ArrayList <>();
this work for you

If you use Kotlin, the next one is a good solution:
myRef.addListenerForSingleValueEvent(object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
val list = dataSnapshot.children.map { it.getValue(YourClass::class.java)!! }
Log.d("TAG", "Value is: $list")
}

Saving and Retriving data to - from Firebase ( deprecated ver 2.4.2 )
Firebase fb_parent = new Firebase("YOUR-FIREBASE-URL/");
Firebase fb_to_read = fb_parent.child("students/names");
Firebase fb_put_child = fb_to_read.push(); // REMEMBER THIS FOR PUSH METHOD
//INSERT DATA TO STUDENT - NAMES I Use Push Method
fb_put_child.setValue("Zacharia"); //OR fb_put_child.setValue(YOUR MODEL)
fb_put_child.setValue("Joseph"); //OR fb_put_child.setValue(YOUR MODEL)
fb_put_child.setValue("bla blaaa"); //OR fb_put_child.setValue(YOUR MODEL)
//GET DATA FROM FIREBASE INTO ARRAYLIST
fb_to_read.addValuesEventListener....{
public void onDataChange(DataSnapshot result){
List<String> lst = new ArrayList<String>(); // Result will be holded Here
for(DataSnapshot dsp : result.getChildren()){
lst.add(String.valueOf(dsp.getKey())); //add result into array list
}
//NOW YOU HAVE ARRAYLIST WHICH HOLD RESULTS
for(String data:lst){
Toast.make(context,data,Toast.LONG_LENGTH).show;
}
}
}

mDatabase.child("token").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot:dataSnapshot.getChildren())
{
String key= snapshot.getKey();
String value=snapshot.getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(ListUser.this,databaseError.toString(),Toast.LENGTH_SHORT).show();
}
});
Only work If child have no SubChild

Works Like a Charm
final DatabaseReference senderDb = FirebaseDatabase.getInstance().getReference(Constant.NODE_MESSAGE).child(myId + "_" + otherId);
senderDb.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> td = (HashMap<String,Object>) dataSnapshot.getValue();
for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
DatabaseReference objRef = senderDb.child( childDataSnapshot.getKey());
Map<String,Object> taskMap = new HashMap<String,Object>();
taskMap.put("is_read", "1");
objRef.updateChildren(taskMap); //should I use setValue()...?
Log.v("Testing",""+ childDataSnapshot.getKey()); //displays the key for the node
}
//notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

You Need to write a custom Deserializer and then loop it and get the values of the hasmap.
Custom Deserializer:-
public class UserDetailsDeserializer implements JsonDeserializer<AllUserDetailsKeyModel> {
/*
bebebejunskjd:{
"email": "akhilbv1#gmail.com",
"mobileNum": "12345678",
"password": "1234567",
"username": "akhil"}*/
#Override public AllUserDetailsKeyModel deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
final JsonObject jsonObject = json.getAsJsonObject();
Gson gson = new Gson();
Type AllUserDetailsResponseModel =
new TypeToken<HashMap<String, AllUserDetailsResponseModel>>(){}.getType();
HashMap<String, AllUserDetailsResponseModel> user =
gson.fromJson(jsonObject, AllUserDetailsResponseModel);
AllUserDetailsKeyModel result = new AllUserDetailsKeyModel();
result.setResult(user);
return result;
}
}
The code in comments is my object model and u should replaceAllUserDetailsKeyModel with your model class and add this to the rest client like below:-
private Converter.Factory createGsonConverter() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(AllUserDetailsKeyModel.class, new UserDetailsDeserializer());
Gson gson = gsonBuilder.create();
return GsonConverterFactory.create(gson);
}
This the custom Convertor for Retrofit.
In your onResponse you just loop with hasmaps and get value by key and my model class looks like below:-
public class AllUserDetailsKeyModel {
private Map<String, AllUserDetailsResponseModel> result;
public Map<String, AllUserDetailsResponseModel> getResult() {
return result;
}
public void setResult(Map<String, AllUserDetailsResponseModel> result) {
this.result = result;
}
}
probably you need to give a Type T where T is your data Type and my model consists only of a hashmap and getters and setters for that.
And finally set Custom Convertor to retrofit like below:- .addConverterFactory(createGsonConverter())
Let me know if you need more clarifications.

Use GenericTypeIndicator to get List of Child Node from Firebase ArrayList structured DataBase
//Start of Code
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener(){
#Override
public void onDataChange(DataSnapshot snapshot){
GenericTypeIndicator<List<YourClassName>> t = new GenericTypeIndicator<List<YourClassName>>{};
List<YourClassName> messages = snapshot.getValue(t);
Log.d("Get Data Size", messages.size());
}
}
#Override
public void onCancelled(FirebaseError firebaseError){
Log.e("The read failed: ",firebaseError.getMessage());
}
});

your problem is why your code doesn't work.
this your code:
Firebase ref = new Firebase(FIREBASE_URL);
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
Log.e("Count " ,""+snapshot.getChildrenCount());
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
<YourClass> post = postSnapshot.getValue(<YourClass>.class);
Log.e("Get Data", post.<YourMethod>());
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.e("The read failed: " ,firebaseError.getMessage());
}
})
you miss the simplest thing: getChildren()
FirebaseDatabase db = FirebaseDatabase.getInstance();
DatabaseReference reference = FirebaseAuth.getInstance().getReference("Donald Trump");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int count = (int) dataSnapshot.getChildrenCount(); // retrieve number of childrens under Donald Trump
String[] hairColors = new String[count];
index = 0;
for (DataSnapshot datas : dataSnapshot.getChildren()){
hairColors[index] = datas.getValue(String.class);
}
index ++
for (int i = 0; i < count; i++)
Toast(MainActivity.this, "hairColors : " + hairColors[i], toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

ArrayList<String> keyList = new ArrayList<String>();
mKeyRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childDataSnapshot : dataSnapshot.getChildren()) {
String temp = childDataSnapshot.getKey();
keyList.add(temp);
i = keyList.size();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
This code is working fine to add all firebase key into arraylist, you can do it with firebase values, of other static values.

DatabaseReference mRootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference mMainMenuRef = mRootRef.child("tut_master");//main
DatabaseReference mSubMenuRef = mMainMenuRef.child("english");//sub
List<Tutorial> tutorialNames=new ArrayList<>();
mSubMenuRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
long id = ds.child("id").getValue(Long.class);
String name = ds.child("name").getValue(String.class);
Tutorial tut = new Tutorial();
tut.setTutId(id+"");
tut.setTutName(name);
tutList.add(tut);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

private FirebaseDatabase firebaseDatabase= FirebaseDatabase.getInstance();
private DatabaseReference databaseReference= firebaseDatabase.getReference();
private DatabaseReference mChildReference= databaseReference.child("data");
mChildReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
User commandObject = ds.getValue(User.class);
Log.d("TAG", commandObject.getMsg());
}
Toast.makeText(MainActivity.this,dataSnapshot.toString(),Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
This will help you, you just have to create a model class containing String msg.

Use Gson is my favorite solution.
mFirebaseRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Type StringListType = new TypeToken<List<String>>(){}.getType();
List<String> td = new Gson().fromJson(dataSnapshot.getValue(), StringListType);
}
});
if you think the code to get TypeToken is unintuitive. You can write a class to contain all types you need. So next time, you can get those types quickly.
class TypeTokens{
static public final Type StringListType = new TypeToken<List<String>>(){}.getType();
static public final Type StringMapType = new TypeToken<Map<String, String>>(){}.getType();
static public final Type LongMapType = new TypeToken<Map<String, Long>>(){}.getType();
static public final Type DateMapType = new TypeToken<Map<String, Date>>(){}.getType();
}

Here goes my 2 cents contribution (in Kotlin):
private fun getData(childUid:String) {
refDB = firebaseDB.reference.child(MAIN_DATABASE_FOLDER).child(childUid)
if(childEventDataListener == null) {
childEventDataListener = object : ChildEventListener {
override fun onChildAdded(snapshot: DataSnapshot, previousChildName: String?) {
for(snap in snapshot.children) {
val newParcel = snapshot.getValue(YourClassConverter::class.java)!!
}
}
override fun onChildChanged(snapshot: DataSnapshot, previousChildName: String?) { }
override fun onChildRemoved(snapshot: DataSnapshot) { }
override fun onChildMoved(snapshot: DataSnapshot, previousChildName: String?) {}
override fun onCancelled(error: DatabaseError) {}
}
refDB.addChildEventListener(childEventDataListener!!)
}
}
The class YourClassConverter shall follow this rule as noted in the getValue header's comment shown below. I prefer to use this converter since I can control the default values passed when some of them are not defined in the firebase.
This method is used to marshall the data contained in this snapshot into a class of your choosing. The class must fit 2 simple constraints:
The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized
An example class might look like:
class Message {
private String author;
private String text;
private Message() {}
public Message(String author, String text) {
this.author = author;
this.text = text;
}
public String getAuthor() {
return author;
}
public String getText() {
return text;
}
}
// Later
Message m = snapshot.getValue(Message.class);

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