I want to get data from this firebase-database (the picture below) into an ArrayListOf< Product> when Product class is :
data class Product(
val title:String,
val photoURL:String,
val description:String,
val price:Double
)
//and i want to make an array like this
val r = arrayListOf<Product>()
so basicly i want to make array list of Firebase_Database_products
any help is appreciated :)
just for readers in future here is the required code in Kotlin:
val products = arrayListOf<Product>()
val ref = FirebaseDatabase.getInstance().getReference("products")
ref.addValueEventListener(object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
for (productSnapshot in dataSnapshot.children) {
val product = productSnapshot.getValue(Product::class.java)
products.add(product!!)
}
System.out.println(products)
}
override fun onCancelled(databaseError: DatabaseError) {
throw databaseError.toException()
}
})
}
and you have to initialize variables in Product class like this :
data class Product(
val title:String = "",
val photo:String = "",
val description:String = "",
val price:Double = -1.0
)
if you leave it without initializing you will get class does not define a no-argument constructor error
Something like this should do the trick:
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("products");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
ArrayList<Product> products = new ArrayList<Product>();
for (DataSnapshot productSnapshot: dataSnapshot.getChildren()) {
Product product = productSnapshot.getValue(Product.class);
products.add(product);
}
System.out.println(products);
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
}
A few things to note:
This code throws away the key of each product (p1 and p2 in your JSON). You may need these keys if you later want to modify or delete the product, so should consider storing them in your Product class. Also see: Is there a way to store Key in class which I cast from Firebase object?
You really owe it to yourself and to us to spend some time in the documentation reading up on listeners and queries.
Related
Unable to extract information from the datasnapshot received from firebase.
Currently, I am able to get the dataSnapshot from firebase, but I am having problems extracting the information from it.
In the example below I have a lobby with the code "81MUB" and inside I have a list of players (only using one player in the example). Data from FireBase
{
"81MUB": [
{
"name": "Alejandro",
"points": 0
}
]
}
Data Class
data class Player(
val name: String,
val points: Int
)
Listener
fun getCode(): String {
val index = ('A'..'Z') + ('1'..'9')
var code = ""
for (i in 0..4){
code += index[Random().nextInt(index.size)]
}
return code
}
class MviewModel : ViewModel() {
private val _Players: MutableLiveData<MutableList<Player>> =
MutableLiveData(mutableListOf<Player>(Player("Alejandro", 0)))
private var _LobbyCode: String = ""
private val dataBase = FirebaseDatabase.getInstance()
fun getPlayer(): MutableLiveData<MutableList<Player>> = _Players
fun createLobby() {
_LobbyCode = getCode()
}
fun listener() {
val postListener = object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
}
override fun onCancelled(databaseError: DatabaseError) {
// Getting Post failed, log a message
}
}
dataBase.reference.child(_LobbyCode).addValueEventListener(postListener)
}
}
Any tips?
Each time you call getCode() you are generating a new random code. When reading data, you always use the exact same code that exists in the database. So in code, it should look like this:
val db = Firebase.database.reference
val codeRef = db.child("81MUB")
codeRef.get().addOnCompleteListener {
if (it.isSuccessful) {
val snapshot = it.result
val name = snapshot.child("name").getValue(String::class.java)
val points = snapshot.child("points").getValue(Long::class.java)
Log.d("TAG", "$name/$points")
} else {
Log.d("TAG", error.getMessage()) //Never ignore potential errors!
}
}
The result in the logcat will be:
Alejandro/0
If you however want to map the 81MUB node into an object of type Player, then your data class should look like this:
data class Player(
val name: String? = null,
val points: Int? = null
)
And in code:
val db = Firebase.database.reference
val codeRef = db.child("81MUB")
codeRef.get().addOnCompleteListener {
if (it.isSuccessful) {
val snapshot = it.result
val player = snapshot.getValue(Player::class.java)
Log.d("TAG", "${player.name}/${player.points}")
} else {
Log.d("TAG", error.getMessage()) //Never ignore potential errors!
}
}
Which will produce the exact same output as above.
You might also take into consideration, using the DatabaseReference#push() method which:
Create a reference to an auto-generated child location. The child key is generated client-side and incorporates an estimate of the server's time for sorting purposes.
Instead of using your codes.
So, my app does is a QR code scanner that adds the QR id to the current user UID. I first verify if the user already did that scan; if not, that id is added to the firebase table; otherwise, it will create that table.
This is my code:
private fun infoAdd(str2: String, view: View) {
val currentUser = auth.currentUser?.uid
val postReference = FirebaseDatabase.getInstance().getReference("organsUsers")
val dbView = postReference.child(currentUser.toString())
val postListener = object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val org = snapshot.child("uOrgans")
if (org != null) {
val post = org.getValue(String::class.java)
dbView.child("uOrgans").setValue("$post,$str2")
} else {
dbView.child("uOrgans").setValue(str2)
}
}
override fun onCancelled(databaseError: DatabaseError) {
}
}
dbView.addValueEventListener(postListener)
}
The str2 it's the string of the QR id.
This is what happens to Firebase:
Please Help!!!!
I first verify if the user already did that scan; if not, that id is added to the firebase table; otherwise, it will create that table.
It doesn't make any sense because in both cases you are "setting" the value of str2 into the database, that's why you see that behavior of highlighting that operation in yellow. Because a Firebase Realtime Database is a NoSQL database and is structured as pairs of keys and values, every node is a Map, which means that when using a setValue() operation, the old value is replaced with the new one.
If you want to check if the value of uOrgans exists, then update it for example, please use the following lines of code:
val uid = FirebaseAuth.getInstance().currentUser!!.uid
val rootRef = FirebaseDatabase.getInstance().reference
val uidRef = rootRef.child("organsUsers").child(uid)
val valueEventListener = object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val org = snapshot.child("uOrgans")
if(org.exists()) {
val post = org.getValue(String::class.java)
dbView.getRef().updateChildren(mapOf("uOrgans" to "$post,$str2")) //Update it
Log.d("TAG", $post,$str2)
} else {
uidRef.child("uOrgans").setValue(str2)
}
}
override fun onCancelled(databaseError: DatabaseError) {
Log.d("TAG", databaseError.getMessage()) //Don't ignore potential errors!
}
}
uidRef.addListenerForSingleValueEvent(valueEventListener)
If doesn't exist, the str2 is added to the database.
One thing to mention, if uOrgans doesn't exist, none of its parents (organsUsers and the UID) nodes will not exist.
I don't know why I got stuck in a problem that the chatList is not sorting by the last message time or by the most recent message. I have tried storing timestamp in the database and orderChildBy timestamp but it still not working. not working means the list get not sort after every message and keep showing the list as the sorted after first message.
Look at the image how chats are disordered!
This is the way I created chatList in the firebaseDatabase in ChatActiviy on sendMessage:
val timeAgo = Date().time
val myTimeMap = HashMap<String, Any?>()
myTimeMap["timestamp"] = timeAgo
myTimeMap["id"] = friendId
val friendTimeMap = HashMap<String, Any?>()
friendTimeMap["timestamp"] = timeAgo
friendTimeMap["id"] = currentUserID
val chatListSenderReference = dbRef.child("ChatList").child(currentUserID).child(friendId)
chatListSenderReference.keepSynced(true)
chatListSenderReference.addListenerForSingleValueEvent(object : ValueEventListener{
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(p0: DataSnapshot) {
if(!p0.exists()){
chatListSenderReference.updateChildren(friendTimeMap)
}
val chatListReceiverReference = dbRef.child("ChatList").child(friendId).child(currentUserID)
chatListReceiverReference.updateChildren(myTimeMap)
}
})
On retrieving the chatlist in recyclerView, I am trying to get the users details for each userswho is presented as the child of currentUser in database. (Chatlist>>CurrentUserId)
EDITED
private fun retrieveChatList() {
usersChatList = ArrayList()
val userRef = dbRef.child("ChatList").child(currentUserID).orderByChild("timestamp")
userRef.addValueEventListener(object : ValueEventListener
{
override fun onCancelled(error: DatabaseError) {
}
override fun onDataChange(snapshot: DataSnapshot)
{
(usersChatList as ArrayList<String>).clear()
if (snapshot.exists()){
for (dataSnapshot in snapshot.children){
val userUid = dataSnapshot.key
if (userUid != null) {
(usersChatList as ArrayList<String>).add(userUid)
}
}
readChatList()
}
}
})
}
private fun readChatList() {
mUsers = ArrayList()
val userRef = FirebaseFirestore.getInstance().collection("Users")
userRef.get()
.addOnSuccessListener { queryDocumentSnapshots ->
mUsers?.clear()
for (documentSnapshot in queryDocumentSnapshots) {
val user = documentSnapshot.toObject(User::class.java)
for (id in usersChatList!!){
if (user.getUid() == id){
(mUsers as ArrayList<User>).add(user)
}
}
}
retrieveGroupChatList()
chatListAdapter?.notifyDataSetChanged()
chatListAdapter = context?.let { ChatListAdapter(it, (mUsers as ArrayList<User>), true) }
recyclerViewChatList.adapter = chatListAdapter
}.addOnFailureListener { e ->
Log.d(ContentValues.TAG, "UserAdapter-retrieveUsers: ", e)
}
}
And this is the chatListAdapter for friend info
private fun friendInfo(fullName: TextView, profileImage: CircleImageView, uid: String) {
val userRef = FirebaseFirestore.getInstance().collection("Users").document(uid)
userRef.get()
.addOnSuccessListener {
if (it != null && it.exists()) {
val user = it.toObject(User::class.java)
Picasso.get().load(user?.getImage()).placeholder(R.drawable.default_pro_pic).into(profileImage)
fullName.text = user?.getFullName()
}
}
}
This is the picture of the realtime database and has a model class as ChatList, every time when I send or receive a message timestamp gets an update.
and another picture of Users in the firestore and has a model class as Users .
SOLUTION
I have a solution which works, Here i create or update a field as lastMessageTimestamp in the Firestore Users collection so the users now can sort by the lastMessageTimestamp .
val timeAgo = Date().time
val myFSMap = HashMap<String, Any?>()
myFSMap["timestamp"] = timeAgo
val friendFSMap = HashMap<String, Any?>()
friendFSMap["timestamp"] = timeAgo
//firebase chatlist references.
val chatListSenderReference = dbRef.child("ChatList").child(currentUserID).child(friendId)
val chatListReceiverReference = dbRef.child("ChatList").child(friendId).child(currentUserID)
//Firestore Users references.
val chatListSenderRef = fStore.collection("Users").document(currentUserID)
val chatListReceiverRef = fStore.collection("Users").document(friendId)
chatListSenderReference.addListenerForSingleValueEvent(object : ValueEventListener{
override fun onDataChange(p0: DataSnapshot) {
if(!p0.exists()){
chatListSenderReference.setValue(friendId)
//update the timestamp in Users collection
chatListSenderRef.update(myFSMap)
}
chatListReceiverReference.setValue(currentUserID)
chatListReceiverRef.update(friendFSMap)
override fun onCancelled(p0: DatabaseError) {
}
}
})
And at the time of reading, I use orderBy for Users
val userRef = FirebaseFirestore.getInstance().collection("Users").orderBy("lastMessageTimestamp" , Query.Direction.ASCENDING)
But It is not the complete solution because it seems like that i read and write the lastMessageTimestamp each time on messaging, which can Increase the Firebase Billing Amount to huge scary numbers. so i still need of a solution.
Simple trick is orderBy id of message. Because the id which generated by firebase base on realtime + a few factors. So let's try order by Id instead of ur timestamp. (note: just id which generated by firebase)
enter code hereSaw your post don't know if it might be useful this late hour, provided the only thing you want from firestone is the user full identity, like the name, picture etc use the userid and save the full details to android database then retrieve the identity using the Id from chatlist firebase database that matches userid
Your code might look like this
Read from chatlist firebase database
Retrieve the sender Id and time
Use the id to retrieve already added info of the person on android database
your model should contain variable for retrieve time from database
Then add all to list
After that use a comparator to sort the arraylist/list base on time
Then notify adapter change
{` ......
userDao = UserDatabase.getUserDatabase(requireContext()).userDao();
}
private void sortChatList() {
reference.child("chatlist").child(firebaseUser.getUid()).orderByChild("time").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
list.clear();;
for (DataSnapshot snapshot : dataSnapshot.getChildren()){
String userID = Objects.requireNonNull(snapshot.child("chatid").getValue()).toString();
String time = snapshot.child("time").getValue().toString();
Chatlist chatlist = new Chatlist();
UserDB userDB = userDao.getAll(userID);
chatlist.setDate(time);
chatlist.setUserName(userDB.getUserName());
chatlist.setUserID(userID);
list.add(chatlist);
}
Collections.sort(list, new Comparator<Chatlist>() {
#Override
public int compare(Chatlist o1, Chatlist o2) {
return Integer.valueOf(o2.getTime().compareTo(o1.getTime()));
}
});
if (adapter != null) {
adapter.notifyDataSetChanged();
.........
`}
I don't know why I got stuck on a problem that the chatList is not sorting by the last message time or by the most recent message. I have tried by storing timestamp in the database and orderChildBy timestamp but it still not working.
This is the way how I created chatList in the firebaseDatabase
val timeAgo = Date().time
val myTimeMap = HashMap<String, Any?>()
myTimeMap["timestamp"] = timeAgo.toString()
myTimeMap["id"] = friendId
val friendTimeMap = HashMap<String, Any?>()
friendTimeMap["timestamp"] = timeAgo.toString()
friendTimeMap["id"] = currentUserID
val chatListSenderReference = dbRef.child("ChatList").child(currentUserID).child(friendId)
chatListSenderReference.keepSynced(true)
chatListSenderReference.addListenerForSingleValueEvent(object : ValueEventListener{
override fun onCancelled(p0: DatabaseError) {
}
override fun onDataChange(p0: DataSnapshot) {
if(!p0.exists()){
chatListSenderReference.updateChildren(friendTimeMap)
}
val chatListReceiverReference = dbRef.child("ChatList").child(friendId).child(currentUserID)
chatListReceiverReference.updateChildren(myTimeMap)
}
})
on retrieving the chatlist in recyclerView
mUsers = ArrayList()
val userRef = dbRef.child("ChatList").child(currentUserID).orderByChild("timestamp")
userRef.addValueEventListener(object : ValueEventListener
{
override fun onCancelled(error: DatabaseError) {
}
override fun onDataChange(snapshot: DataSnapshot)
{
(mUsers as ArrayList).clear()
snapshot.children.forEach {
val userUid = it.key
if (userUid != null) {
(mUsers as ArrayList).add(User(uid = userUid))
}
}
retrieveGroupChatList()
chatListAdapter?.notifyDataSetChanged()
chatListAdapter = context?.let { ChatListAdapter(it, (mUsers as ArrayList<User>), true) }
recyclerViewChatList.adapter = chatListAdapter
}
})
this is the picture of database, every time when i send or receive message timestamp get update.
You should store the timestamp of messages and then use val chatListSenderReference = dbRef.child("ChatList").child(currentUserID).orderByChild("timestamp")
Not sure if this will work for your case but for my Chat App, I had a list of the message and all I did is to sort the list
//sort method - takes a list to be sorted
private fun sortMessagesByDate(messages: MutableList<Message>) {
//sort messages by Date
messages.sortWith(compareBy { it.timestamp })
}
Method for looping through the ContactList
// method for obtaining contacts and adding them to the lists
private fun getAllContacts() {
val currentUserPhoneCredential = auth.currentUser?.phoneNumber!!
firestore.collection("Contacts")
.whereNotEqualTo("phoneNumber", currentUserPhoneCredential)
.get().addOnSuccessListener { querySnapshot ->
for (doc in querySnapshot) {
val user = doc.toObject(User::class.java)
//I have 2 lists one with just the names and another with the User Object
contactsList.add(user)
contactsNames.add(user.name!!)
}
adapter.notifyDataSetChanged()
}
Then on ListView's Adapter passing in the Names List(contactsNames)
adapter =
ArrayAdapter(requireActivity(), android.R.layout.simple_list_item_1, contactsNames)
Thereafter when a name is clicked at a specific position the app navigates to the DisplayMessage Fragment taking a UserObject corresponding to the clicked contact.
//implement listView onClick
binding.listView.setOnItemClickListener { _, _, i, _ ->
/*when a name is clicked on the ListView at a specific position the app navigates
to the DisplayMessage Fragment taking a UserObject corresponding to the
clicked contact.*/
findNavController().navigate(ChatFragmentDirections
.actionChatFragmentToMessageFragment(contactsList[i]))
}
You could also use a RecyclerView to display the names of the contacts.
I have two methods, in one I create a new list item, in the second I update the current list item.
private fun addTarget() {
val name = nameEditText?.text.toString().trim()
val description = descriptionEditText?.text.toString().trim()
if (!TextUtils.isEmpty(name)) {
val id: String = databaseReference?.push()?.key.toString()
val target = Target(guid = id, name = name, description = description)
databaseReference?.child(id)?.setValue(target)
} else Log.d("some", "Enter a name")
}
private fun updateTarget() {
val name = nameEditText?.text.toString().trim()
val description = descriptionEditText?.text.toString().trim()
val map = mapOf("name" to name, "description" to description)
databaseReference?.child(arguments?.getString(KEY_TARGET_GUID, "") ?: "")?.updateChildren(map)
}
I need to clearly separate these two concepts, so there is a problem in the condition.
button?.setOnClickListener { if (condition?????) addTarget() else updateTarget() }
For example, in the Realm there is a method copyToRealmOrUpdate which looks for the field and if it finds it updates it if not then creates a new note. How can I do something like this in firebase?
I resolved my problem next:
When I go to the fragment I pass the guid from the list of all elements and if it is empty then I add if not then update.
button?.setOnClickListener {
if (arguments?.getString(KEY_TARGET_GUID, "").isNullOrEmpty()) addTarget()
else updateTarget()
}
I don't know how this is a good solution.
This is possible in Firebase if you are using exist() method like in the following lines of code:
val valueEventListener = object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
if (dataSnapshot.exists()) {
//Do the update
} else {
//Do the addition
}
}
override fun onCancelled(databaseError: DatabaseError) {
Log.d(TAG, databaseError.getMessage()) //Don't ignore errors!
}
}
databaseReference.child("-LaVYDBpwiIcwhe9qz2H").addListenerForSingleValueEvent(valueEventListener)