Jump to Firebase parent Nodes from Child Nodes - android

Hello all i have a my fire-base structure like this
Firebase Database
I have an array list inside an node in fire-base , I need to loop through this list and jump to each ID to get information i need like the database photo shows.
what I've tried so far
public static void checkIfCurrentUserLiked(final HomeFragment.PostsViewHolder postsViewHolder, String postKey) {
userID = Objects.requireNonNull(FirebaseAuth.getInstance().getCurrentUser()).getUid();
likesRef = FirebaseDatabase.getInstance().getReference().child("likes");
postsRef = FirebaseDatabase.getInstance().getReference().child(postKey);
postsRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.hasChild("likes")) {
for (DataSnapshot ds : dataSnapshot.child("likes").getChildren()) {
likesRef.child(Objects.requireNonNull(ds.getValue()).toString())
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
Like like = snapshot.getValue(Like.class);
if (like != null && like.getLikedUserID().equals(userID)) {
postsViewHolder.likesImage.setImageResource
(R.drawable.ic_item_home_post_like_filled);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) { }
});
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) { }
});
}
i have no error , just nothing happens , data are not fetched as expected


Change this:
postsRef = FirebaseDatabase.getInstance().getReference().child(postKey);
into this:
postsRef = FirebaseDatabase.getInstance().getReference().child("posts").child(postKey);
According to your database, you have node posts before the postKey, therefore you need to add it when referencing to a location.

Related

How can i retrieve a specific data from a firebase child node into Android studio

referenc2= FirebaseDatabase.getInstance().getReference("messageCounter").child("node");
referenc2.addValueEventListener(new ValueEventListener() {
public void onDataChange(#NonNull DataSnapshot snapshot) {
String count= Integer.parseInt(snapshot.child("cnt").getValue(String.class));
}
#Override public void onCancelled(#NonNull DatabaseError error) {
}
});
I need to retrieve the value stored inside the cnt node into a variable in android studio. can anyone help?

if you want to get value of specific node or child node like this
Here if you want to get child node(address) value. You can get it in this way
DatabaseReference db= FirebaseDatabase.getInstance().getReference().child("RouteCounter").child("node");
db.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
String email = userSnapshot.child("cnt").getValue(String.class);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
throw databaseError.toException();
}
});

Android - How to retrieve data from multiple nodes and display it in a Single list?

I am trying to retrieve data from multiple nodes and store them in a Single List. I am able to do that but the problem is data is getting duplicated if I remove list.clear(); in function getTeam2().
Here is the Screenshot of the Database.
Here is The Code
databaseReference = FirebaseDatabase.getInstance().getReference("Teams")
.child(team1).child("Players");
databaseReference.orderByChild("playertype").equalTo("Wk")
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
mList.clear();
for (DataSnapshot dataSnapshot : snapshot.getChildren()) {
Player player = dataSnapshot.getValue(Player.class);
mList.add(player);
getTeam2(mList);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
return view;
}
private void getTeam2(final List<Player> mList) {
DatabaseReference team = FirebaseDatabase.getInstance().getReference("Teams")
.child(team2).child("Players");
team.orderByChild("playertype").equalTo("Wk")
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
for (DataSnapshot dataSnapshot : snapshot.getChildren()) {
Player player = dataSnapshot.getValue(Player.class);
mList.add(player);
bar.setVisibility(View.INVISIBLE);
}
adapter = new PlayerAdapter(getContext(), WKFragement.this.mList);
recyclerView.setAdapter(adapter);
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
If I use list.clear(); in team2 function then it only displays the members of team2.
What changes should I make?

How to perform nested query in firebase realtime database?

I fetched data from firebase database, inside OnDataChange method I want to perform another query based on the data I fetched previously. Before going to another activity I fetched all my data using a callback function MyCallback. Here listAllRequest contains expected data but userMap contains null. How can I ensure userMap contains data before going to another activity?
public void readRequestData(final Outgoing.MyCallback myCallback) {
groupDatabase = FirebaseDatabase.getInstance().getReference("Users").child(user.getUid()).child("outgoing");
userInfoRef= FirebaseDatabase.getInstance().getReference("UserInfo");
groupDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
listAllRequest.clear();
for(DataSnapshot childSnapshot: dataSnapshot.getChildren())
{
final BookRequestData bookRequestData = childSnapshot.getValue(BookRequestData.class);
listAllRequest.add(bookRequestData);
userInfoRef.child(bookRequestData.getOwnerId()).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
User user=dataSnapshot.getValue(User.class);
userMap.put(bookRequestData.getReqId(),user);
Log.e("outgoing",user.getName());
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
myCallback.onCallback(listAllRequest);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {}
});
}

Retrieving nested data from multiple records in a Firebase Database

I'm trying to retrieve nested data from multiple records and display them in a ListView. My data is recorded like so:
I want to display the GroupNumber and the GroupVaccinationDate of all GroupVaccinations recorded in a listView but at the moment the listView remains empty when I run the following code:
listView = (ListView)findViewById(R.id.listItemAllGroupVaccinations);
databaseReference = FirebaseDatabase.getInstance().getReference("groupVaccinations");
groupVaccinations = new ArrayList<>();
protected void onStart(){
super.onStart();
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot groupVaccinationSnapshot : dataSnapshot.getChildren()){
GroupVaccination groupVaccination = groupVaccinationSnapshot.getValue(GroupVaccination.class);
groupVaccinations.add(groupVaccination);
}
AllGroupVaccinationList groupVaccinationInfoAdapter = new AllGroupVaccinationList(ActivityAllGroupVaccinations.this, groupVaccinations);
listView.setAdapter(groupVaccinationInfoAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
Any help or suggestions would be greatly appreciated!

Gaston's answer will show you all vaccinations in a single group. If instead you want to show all vaccinations in all groups, you can loop over the nested snapshots in your onDataChange:
databaseReference = FirebaseDatabase.getInstance().getReference("groupVaccinations");
groupVaccinations = new ArrayList<>();
AllGroupVaccinationList groupVaccinationInfoAdapter = new AllGroupVaccinationList(ActivityAllGroupVaccinations.this, groupVaccinations);
listView.setAdapter(groupVaccinationInfoAdapter);
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot groupVaccinationSnapshot : dataSnapshot.getChildren()){
for(DataSnapshot vaccinationSnapshot : groupVaccinationSnapshot.getChildren()){
GroupVaccination groupVaccination = vaccinationSnapshot.getValue(GroupVaccination.class);
groupVaccinations.add(groupVaccination);
}
}
groupVaccinationInfoAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
});
I also changed the code to call groupVaccinationInfoAdapter.notifyDataSetChanged(), so that you can keep using the same adapter and update it if needed.

You will need to go one level deeper where your id -LZk5tpB5PXqHVJkj8Vz (GroupID) contains all the sub pushKeys (groupVaccinationID) with data inside.
listView = (ListView)findViewById(R.id.listItemAllGroupVaccinations);
databaseReference = FirebaseDatabase.getInstance().getReference("groupVaccinations").child("-LZk5tpB5PXqHVJkj8Vz");
groupVaccinations = new ArrayList<>();
protected void onStart(){
super.onStart();
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot groupVaccinationSnapshot : dataSnapshot.getChildren()){
GroupVaccination groupVaccination = groupVaccinationSnapshot.getValue(GroupVaccination.class);
groupVaccinations.add(groupVaccination);
}
AllGroupVaccinationList groupVaccinationInfoAdapter = new AllGroupVaccinationList(ActivityAllGroupVaccinations.this, groupVaccinations);
listView.setAdapter(groupVaccinationInfoAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
EDIT
The -LZk5tpB5PXqHVJkj8Vz child should be avoided since is hardcoded to show you this example, instead, you should take that child key from where you get your GroupID, doing that you can get as Frank says all the vaccinations from each GroupID.

Firebase - Adapter is called before my array has any elements and returns an empty RecyclerView

I'm facin a really weird problem, Im calling two nodes in my database , from one node I get all my user ids , then I just loop inside my user node to get the user metadata. The problem is that when I run the debugger, it seems like the mAdapter is beign called before the data is beign fetched. So my adapter set the recyclerview with no data. After the adapter has been called, my query fetching the user begins and the array is populated normally
This is what I have done so far
mDatabase.child("teamsNode").child(teamID).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot snapshot : dataSnapshot.getChildren()){
mDatabase.child("users").child(snapshot.getKey()).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
UserModel model = dataSnapshot.getValue(UserModel.class);
String playerName = model.getName();
model.setName(playerName);
mArrayPlayers.add(model);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) { }
});
}
mAdapter = new PlayersAdapter(mArrayPlayers,mContext,R.layout.recycler_row);
if(mAdapter.getItemCount()>0)
mRecyclerView.setAdapter(mAdapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) { }
});
As you can see, I set the adapter to the recyclerview after the first foreach that fetchs all the data, I know that beign asynchronous I need to wait for the inner mDatabase to be done but if I move the setting of the adapter one line above to wait for the second call to finish it does the same, any idea?
Database structure is like this
teamsNode
|__Jm2KSMjslpow2Ipoasz : true
|__601KSMjsldfjd2Ipos0 : true
|__asgm2Kshalpow2IposJ : true
users
|__Jm2KSMjslpow2Ipoasz
|_____name: randomname1
|__601KSMjsldfjd2Ipos0
|_____name: randomname2
|__asgm2Kshalpow2IposJ
|_____name: randomname3
Recyclerview is not populated. Any idea?
A weird thing is that sometimes runing it with the debugger does fill the data, but its rarely to happend.

If you want to only initialize the adapter when all data is loaded, you will need to do so in the nested onDataChange callback:
mDatabase.child("teamsNode").child(teamID).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshotTeam) {
AtomicInteger loadedUserCount = new AtomicInteger(0);
for(DataSnapshot snapshot : dataSnapshotTeam.getChildren()){
mDatabase.child("users").child(snapshot.getKey()).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
UserModel model = dataSnapshot.getValue(UserModel.class);
String playerName = model.getName();
model.setName(playerName);
mArrayPlayers.add(model);
if (loadedUserCount.getAndIncrement() + 1 == dataSnapshotTeam.getChildrenCount()) {
mAdapter = new PlayersAdapter(mArrayPlayers,mContext,R.layout.recycler_row);
if(mAdapter.getItemCount()>0) {
mRecyclerView.setAdapter(mAdapter);
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
});
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
});

The problem you have is that the calls to the addListenerForSingleValueEvent methods are asynchronous, so they are executed in another thread. When you call the second addListenerForSingleValueEvent this is executed in another thread, while the main thread follows its execution. You have to do the call of your adapter in the answer of your second call addListenerForSingleValueEvent in the onDataChange method. In this way to avoid anomalous operations of your application.

Hope this will help.
mDatabase.child("teamsNode").child(teamID).addListenerForSingleValueEvent(new ValueEventListener() {
mArrayPalyer.clear();//add this
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot snapshot : dataSnapshot.getChildren()){
mDatabase.child("users").child(snapshot.getKey()).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
UserModel model = dataSnapshot.getValue(UserModel.class);
String playerName = model.getName();
model.setName(playerName);
mArrayPlayers.add(model);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
mAdapter = new PlayersAdapter(mArrayPlayers,mContext,R.layout.recycler_row);
mRecyclerView.setAdapter(mAdapter); //makes changes here because you are checking for adapter item count before setting it and this always return null.
}

You can look at my code I am using ValueEventListener just like you and binding the data to recycler view
ValueEventListener postListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
UserListModel userListModel =dataSnapshot1.getValue(UserListModel.class);
userModelArrayList.add(userListModel);
}
userListAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.w(">>value", "loadPost:onCancelled", databaseError.toException());
}
};
//mDatabase is the reference to the Firebase Node
mDatabase.addValueEventListener(postListener);
userListRecyclerView.setLayoutManager(M.gridLayoutRecyclerView(getActivity() , 2));
userListAdapter = new UserListAdapter(getActivity(), userModelArrayList);
userListRecyclerView.setAdapter(userListAdapter);

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