Returning a value in Firebase onDataChange

Returning a value in Firebase onDataChange - android

I am trying to write a firebase app that contains a simple ArrayList that will serve as feed for a list view.
In order to do so I have a singleton that takes care of FirebaseConnection and will fetch the data. This data is then feeded to the list. The problem is the data is first feeded to the list as null then the data is finished retrieving. Any solutions you might have for me?
Here is my code:
public ArrayList< Event > getAllEventsOnFirebase() {
final ArrayList< Event > events = new ArrayList<Event>();
DatabaseReference eventsTable = getDatabaseTableWith(Constants.tableEvents);
eventsTable.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
HashMap<String, Object> event = (HashMap<String, Object>) postSnapshot.getValue();
String eventId = (String) event.get(Constants.taEventUUID);
String eventName = (String) event.get(Constants.taEventName);
String eventAddress = (String) event.get(Constants.taEventAddress);
Event newEvent = new Event(eventId, eventName, eventAddress);
events.add(newEvent);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return events;
}
Also the way I populate the list is as follows:
eventsArray = FirebaseConnection.getInstance().getAllEventsOnFirebase();
EventListAdapter adapter = new EventListAdapter(this, eventsArray);
eventsListView.setAdapter(adapter);

Data is loaded asynchronously from Firebase. Luckily you can populate the ArrayList at any moment, as long as you tell the adapter that you changed it by calling adapter.notifyDataSetChanged().
public ArrayList< Event > getAllEventsOnFirebase(final EventListAdapter adapter,
final ArrayList<Event> events) {
DatabaseReference eventsTable = getDatabaseTableWith(Constants.tableEvents);
eventsTable.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
String eventId = postSnapshot.child(Constants.taEventUUID).getValue(String.class);
String eventName = event.child(Constants.taEventName).getValue(String.class);
String eventAddress = event.child(Constants.taEventAddress).getValue(String.class);
Event newEvent = new Event(eventId, eventName, eventAddress);
events.add(newEvent);
}
adapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
}
Now you can call it as:
ArrayList< Event > events = new ArrayList<Event>();
EventListAdapter adapter = new EventListAdapter(this, eventsArray);
eventsListView.setAdapter(adapter);
FirebaseConnection.getInstance().getAllEventsOnFirebase(adapter, events);

Related

How to get all strings from firebase database

I am trying to store all children of my firebase database into an array list.
Here is my database structure:
I am currently trying to loop through children in order to get the values I need as follows:
private void initializeData(int Destination) {
listItems = new ArrayList<>();
DatabaseReference MyRef = FirebaseDatabase.getInstance().getReference("rideShare");
switch (Destination) {
case 0:
Toast.makeText(getActivity(), "LA BUNDLE", Toast.LENGTH_SHORT).show();
MyRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
for(DataSnapshot snapshot : dataSnapshot.getChildren()) {
String NameValue = snapshot.child("Name").getValue(String.class);
String Price = snapshot.child("Price").getValue(String.class);
String Type = snapshot.child("Trip Type").getValue(String.class);
String Date = snapshot.child("Date").getValue(String.class);
String Destination = "LA";
String Phone = snapshot.child("Phone Number").getValue(String.class);
listingItem newItem = new listingItem(NameValue, Type, Price, Date, Destination, Phone);
listItems.add(newItem);
}
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
//Log.w(TAG , "Failed to read value.",error.toException());
}
});
break;
}
}

Add all the string variables into a POJO class and name the variables same as the child nodes keys. Use snapshot.get(listingItem.class) directly instead.
Refer to this https://stackoverflow.com/a/39861649/3860386

To get those values, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference rideShareRef = rootRef.child("rideShare");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<ListingItem> listItems = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String nameValue = ds.child("Name").getValue(String.class);
String type = ds.child("Trip Type").getValue(String.class);
String price = ds.child("Price").getValue(String.class);
String date = ds.child("Date").getValue(String.class);
String destination = "LA";
String phone = ds.child("Phone Number").getValue(String.class);
ListingItem newItem = new ListingItem(nameValue, type, price, date, destination, phone);
listItems.add(newItem);
}
Log.d("TAG", listItems);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
rideShareRef.addListenerForSingleValueEvent(eventListener);
When you are writting Java code, it's better to use Java Naming conventions. I added this code accordingly.
Also as you probaly see, i have added the declaration of listItems inside onDataChange() method, otherwise it will alwasy be null due the asynchronous behaviour of this method.

Update Values within Push firebase android

This is my firebase data Structure.
Now what basically I want to do is, first there is the Id:"cbn". I have pushed the Location with push().setValue(gpsData). Now based on this id = "cbn", I want to add new Latitude and Longitude in the Location child exactly like shown in the figure above by using "push(). Till now my code is:
mDatabase = FirebaseDatabase.getInstance().getReference().child("Users");
if (busExists) {
// busId = "cbn"
mDatabase.child(busId).child("Location").push().setValue(gpsData);
}
I know I cannot reference busId as child but how can I access that particular node and push my new data to it.
Any Help?
For new question:
public class Users {
private String bus_id;
private HashMap<String, String> coord = new HashMap<>();
public Users() {
}
public String getBus_id() {
return bus_id;
}
public void setBus_id(String bus_id) {
this.bus_id = bus_id;
}
public HashMap<String, String> getCoord() {
return coord;
}
public void setCoord(HashMap<String, String> coord) {
this.coord = coord;
}
}
I implemented it this way:
mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Users bus = new Users();
bus.setBus_id(ds.getValue(Users.class).getBus_id());
Log.e("bus id: ", bus.getBus_id()+""); // I got NULL
busList.add(bus.getBus_id());
arrayAdapter.notifyDataSetChanged();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

You'll need to fire a query to get the push ID of cbn and then add the location from there:
Query query = ref.child("Users").orderByChild("Id").equalTo("cbn");
query.addListenerForSingleValueEvent(new ValueEventListener() {
public void onDataChange(DataSnapshot snapshot) {
for (DataSnapshot user: snapshot.getChildren()) {
user.getRef().child("Location").push().setValue(...);
The loop in onDataChange() is needed, since there may be multiple child nodes matching the query. If there can only be one child with a specific Id, consider storing the users under that Id.
Users
cbd
Locations:...
With this structure you can add a new location without first querying:
ref.child("Users/cbn/Location").push().setValue(...);

how to get all child node list values from Firebase database?

So this is how my database looks like. Each user can add his 3 best players that are stored in userId/My Players/ path as a Map<"Best Players", Player> as it is shown here:
List<String> list = new ArrayList<>();
list.add(first.getText().toString());
list.add(second.getText().toString());
list.add(third.getText().toString());
Players players = new Players(list);
Map<String, Object> map = new HashMap<>();
map.put("Best Players", players);
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
FirebaseDatabase database = FirebaseDatabase.getInstance();
if (user != null) {
DatabaseReference myRef = database.getReference().child("Users").child(user.getUid()).child("My Players");
myRef.setValue(map);
}
Player object contains ArrayList with 3 String objects. So, I would like to go through all users in database and search for each users 0th or 1st or 2nd player from his Best Players list. Any advice how to do that?

In order to display those lists, please use this code:
ListView listView = (ListView) findViewById(R.id.list_view);
ArrayList arrayList = new ArrayList<>();
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Users").child(userId).child("My Players").child("Best Players").child("list");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
#SuppressWarnings("unchecked")
Map<String, Object> map = (Map<String, Object>) dataSnapshot.getValue();
String firstList = (String) map.get("0");
String secondList = (String) map.get("1");
String thirdList = (String) map.get("2");
arrayList.add(firstList + ", " + secondList + ", " + thirdList);
arrayAdapter = new ArrayAdapter<>(this, R.layout.list, arrayList);
listView.setAdapter(arrayAdapter);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
ref.addListenerForSingleValueEvent(eventListener);

you can use code given below: change parameters as per your database
databaseReference.child(Table_Dashboard).orderByChild("title").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
spin = new ArrayList<String>();
// spin.add("Dashboard");
for (DataSnapshot spinnerSnapshot : dataSnapshot.getChildren()) {
String areaName = spinnerSnapshot.child("title").getValue(String.class);
spin.add(areaName);
}
// spin.remove("Family Details");
ArrayAdapter<String> spinnerAdapter = new ArrayAdapter<String>(Dashboard.this, android.R.layout.simple_spinner_item,
spin);
spinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(spinnerAdapter);
dismissprogress();
}
#Override
public void onCancelled(DatabaseError databaseError) {
dismissprogress();
}
});

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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