Hi I am converting Firestore to FirebaseDatabase, I am able to do most of the conversion except for this one that I came accross. I am stuck at .getdocuments and Documentchanges. I think .getdocuments is .getchildren? I do not know what the equivalent of Documentchanges is in the realtime firebase. Please help. Thanks you in advance!
here is the code i want to convert
firestore.collection("Users")
.get()
.addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
#Override
public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
if (!queryDocumentSnapshots.getDocuments().isEmpty()) {
for (final DocumentChange doc : queryDocumentSnapshots.getDocumentChanges()) {
if (doc.getType() == DocumentChange.Type.ADDED) {
if (!doc.getDocument().getId().equals(mAuth.getCurrentUser().getUid())) {
Friends friends = doc.getDocument().toObject(Friends.class).withId(doc.getDocument().getString("id"));
usersList.add(friends);
usersAdapter.notifyDataSetChanged();
refreshLayout.setRefreshing(false);
}
}
}
if(usersList.isEmpty()){
refreshLayout.setRefreshing(false);
mView.findViewById(R.id.default_item).setVisibility(View.VISIBLE);
}
}else{
refreshLayout.setRefreshing(false);
mView.findViewById(R.id.default_item).setVisibility(View.VISIBLE);
}
}
})
There is no direct equivalent in Realtime Database.
The purpose of documentChanges is to know what changes in a set of query results compared to the last time you got results. This only really applies to when you're using a listener to receive realtime updates (which you are not doing here). If you want to know the changes of a DataSnapshot with respect to the prior DataSnapshot you got in a listener, you will have to figure that out for yourself.
But that's kind of beside the point. Your Firestore code here is unnecessarily using document changes to get a list of documents from a single set of results that don't update in real time. If you're not using a realtime listener, then documentChanges actually isn't really the right thing to use. Every document will appear as "ADDED". For a single set of query results, you should just be iterating the list returned by queryDocumentSnapshots.getDocuments().
The equivalent of getDocuments() for a Realtime Database DataSnapshot is just getChildren(), which will give you a way to iterate the child nodes.
Related
I'm developing an app. The app must able to show the latest 10 registered user detail from real-time database. That is, It removes any user older than latest 10 users. Is there any way I can do this? Right now my app is able to access the user details stored in realtime firebase.
Thanks in advance.
That sounds totally feasible. An incredibly simple way is to retrieve 11 users in your app, and then just remove the last one.
ref.orderByChild("descending_timestamp").limitToFirst(11).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int userCount = 0;
for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
if (userCount++ > 10) {
userSnapshot.getRef().remove();
} else {
// TODO: show the user in your app
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
// Getting Post failed, log a message
Log.w(TAG, "load users", databaseError.toException());
}
});
You'll note that I order on descending_timestamp, which is a property that you must add to the data and that allows you to sort the users in reverse chronological order. For more on this, see Firebase Data Desc Sorting in Android
I'm using firebase with android to create a simple chat app. When the user chooses another user to chat with I want to check whether they've chatted together or not.
In onCreate() method I'm retrieving all the rooms that the current user used before, and I'm putting them in an arraylist called MyChatRooms<>.
Then I want to check each room to see the users of the room.
The problem is that the loop I'm using to iterate through rooms name is finishing before I'm able to retrieve any data from the database.
I know there's similar questions to mine, but none of the answers worked for me.
Here's the related code:
if (!MYChatRooms.isEmpty()) {
for (j = 0; j < MYChatRooms.size(); j++) {
roomref.child(MYChatRooms.get(j)).child("First User").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot1) {
if (!dataSnapshot1.getValue().toString().equals(Username) && dataSnapshot1.getValue().toString().equals(NUsername)) {
Users += dataSnapshot1.getValue().toString() + ",,, ";
} else if (dataSnapshot1.getValue().toString().equals(Username)) {
roomref.child(MYChatRooms.get(j)).child("Second User").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot2) {
if (dataSnapshot2.getValue().toString().equals(NUsername)) {
Users += dataSnapshot2.getValue().toString() + ",,, ";
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}
I would suggest that you change the structure of your data. Imagine if a user has 100 chats that means your have to query 200 times to Firebase that of course does not look feasible.
What i would suggest is that your add a recentChat list in every user and whenever a user starts a new chat with someone you add the id of the second user to that list. That way you can track easily with whom the current user has interacted with.
It structure in firebase can look something like this:
User
recentChats
id of the other user
Try to change you database hierarchy or use firestore instead of real time database
Please check the following topic: https://firebase.google.com/docs/database/usage/optimize?
In my case, I had added and index column and limited the query in Firebase Rules.
Right now I'm developing an android app, and I just started to work with Firebase.
My question is: How can I retrieve data from the firebase database, without use listeners ?
In my game, I'm saving the high scores of all the users, and I need to take the data from the database when user go into "leader-boards" page.
I saw some solutions, which is not good for my case.
One of them is:
mRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String value = dataSnapshot.getValue(String.class);
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});
This solution is not good for me, because I cant afford to my app to go into the server every time high score of user is changing, because if I would have 20,000 people who playing at the same time, then the game will stuck.
so I cant use this listener, because it will make the game very slow.
My goal is to to find a way to change the high score, without alerting the other people who is currently playing the game, I mean that I need to update every user score for his own, and when user go to the "leader boards" page, only then I will go to the server.
what is the right solution here ?
Or can I use this listener in another way?
If my question is not clear, then ask me in the comment please.
Thank you !!
my lines:
public static void setUserHighScoreToServer(Context context,boolean isClassic,int scoreNum)
{
com.firebase.client.Firebase mRef;
mRef= new com.firebase.client.Firebase("...");
String name = InternalStorage.getUserName(context);
String classic = "";
if(isClassic)classic="Classic";
else classic="Arcade";
com.firebase.client.Firebase mRefChild = mRef.child(name+classic);
mRefChild.setValue(String.valueOf(scoreNum));
}
This is the OFFICIAL way to retrieve data once without listening for data changes.
// Add all scores in ref as rows
scores.addListenerForSingleValueEvent( new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
for (DataSnapshot child : snapshot.getChildren()) {
...
}
}
}
more information here: https://firebase.google.com/docs/reference/android/com/google/firebase/database/DataSnapshot
If you don´t need to update on real time, you can always do a Rest api call to your database.
Just do a GET call to retrieve your data
https://[PROJECT_ID].firebaseio/[path].json
and you are good to go
You can also update or create new keys using rest api calls.
I am working on the app where I need to pull specific value from the firebase. For this case I need to pull "Score" where "uID" equals current User id. What would be a best way to do so.
Thank you for any help.
Firebase will always return full nodes. So you cannot just return the score for a user. But you can return the common node that both the score and user are under (the one starting with -K...) by using a Firebase query:
DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders");
Query query = leadersRef.orderByChild("uID").equalTo("vUdnKx...");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
for (DataSnapshot child: snapshot.getChildren()) {
System.out.println(child.getKey()+": "+child.child("Score").getValue(Long.class));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
// Getting Post failed, log a message
Log.w(TAG, "onCancelled", databaseError.toException());
// ...
}
})
Note that the code loops over the snapshot in the result. That is because a query will potentially have multiple results. So the snapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result.
For more reading see the Firebase documentation on handling lists and sorting and filtering data.
I have an app which works with users, and offers the possibility to follow certain users, at the current user choice.
Unfortunately, I don't know how to modify data of a user which is not the current user. I have not seen anything like that stated in the Parse.com docs(or i missed).
I have a column in my database in "Users" class called "usersFollowed" and when the current user clicks "Follow" i want to add the current user to the "usersFollowed" list, but adding them like you will see in the following code does not work.
Follow user code:
dialog = ProgressDialog.show(context, "",
"Following...", true);
viewHolder.userFollow.setSelected(true);
viewHolder.userFollow.setText("FOLLOWING");
ParseQuery<ParseUser> userListQuery = ParseUser.getQuery();
userListQuery.whereEqualTo("screenName", parseUserList.get(position).get("screenName").toString());
userListQuery.findInBackground(new FindCallback<ParseUser>() {
#Override
public void done(List<ParseUser> parseObjects, ParseException e) {
parseUserFollowedList = new ArrayList<>();
if (parseObjects.get(0).getList("usersFollowed") == null) {
parseUserFollowedList.add(ParseUser.getCurrentUser());
parseObjects.get(0).addAll("usersFollowed", parseUserFollowedList);
} else {
parseUserFollowedList = parseObjects.get(0).getList("usersFollowed");
parseUserFollowedList.add(ParseUser.getCurrentUser());
parseObjects.get(0).addAll("usersFollowed", parseUserFollowedList);
}
parseObjects.get(0).saveInBackground(new SaveCallback() {
#Override
public void done(ParseException e) {
dialog.dismiss();
}
});
}
});
.saveInBackground does not work because it throws exception: Cannot save info for user that is not logged in".
Can anyone help me in how to do this?
Cheers!
Users may modify only their own data. But the idea of following can be implemented such that only the currentUser's record requires write access: If Jack chooses to follow Jill, then Jack writes to his "following" relation. This works as long as we don't try to represent "followedBy" in Jill's data (which can be achieved instead with a query).
Or consider that the User table represents the private relationship between a real person and your app. It might make better sense to model the idea of a user's public face with your own custom object, and model following relationships between those. I mention this idea elsewhere here and here.