I am developing a chat app but when it comes to viewing friend requests to the user i face a problem that is
When I log queries of Firebase why is it not properly ordered as code ?
This is my code:
// Query for pending requests in the current user
Log.v("AAAAAA", "AAAAAA");
usersRef.child(MainActivity.currentUser.getUid()).child("inpendingfriendreq").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) { // dataSnapShot = inpendingfriendreq node
for (DataSnapshot reqDataSnapShot : dataSnapshot.getChildren()) {
U = reqDataSnapShot;
Log.v("BBBBBBBB", U.toString());
usersRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot sDataSnapshot) { // sDataSnapshot = "users" node DataSnapShot
for (DataSnapshot searchForPendingUserDS : sDataSnapshot.getChildren()) { // searchForPendingUserDS = a user from database (child node of "users" node)
Log.v("CCCCCCC", searchForPendingUserDS.toString());
if (searchForPendingUserDS.getKey().equals(U.getKey())) { // If that user's id equals pending req id
MainActivity.reqArrList.add(new FriendRequest(R.drawable.default_pp, searchForPendingUserDS.child("name").getValue(String.class)));
Log.v("DDDDDDDDD", searchForPendingUserDS.child("name").getValue(String.class));
}
}
Log.v("EEEEEEEE", MainActivity.reqArrList.toString());
//requestsPageUpdated();
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(mContext, "Error querying", Toast.LENGTH_SHORT).show();
}
});
//requestsPageUpdated();
Log.v("FFFFFFFFFF", "FFFFFFFFF");
break;
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(mContext, "Error querying", Toast.LENGTH_SHORT).show();
}
});
It should be:
AAAAAA
BBBBBB
CCCCCC
DDDDDD
CCCCCC
CCCCCC
CCCCCC
EEEEEE
FFFFFF
GGGGGG
But it shows that in the Logcat:
AAAAAA
GGGGGG
BBBBBB
FFFFFF
CCCCCC
DDDDDD
CCCCCC
CCCCCC
CCCCCC
EEEEEE
I know that event listeners are Async but what is the meaning of that ?
Does Async means that the function are waiting to be triggered like Button onClickListener or does it mean that when it's triggered it runs parallel to the main thread? so in the second case that will make sense to my problem.
Any help, please!
Related
I have a very simple code:
// get users poll date, and set in relevant text view
Query query = gameRef.child("users_loto").child("zaalkIb4W0V7MGbekLhqjP34IQi1").orderByChild("pollRank").limitToLast(1);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
nDate = Long.parseLong(ds.child("pollRank").getValue().toString().substring(0, 14));
user_result.setText(String.valueOf(nDate));
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
};
query.addListenerForSingleValueEvent(valueEventListener);
I ordered it by pollRank - it is the same number as the child name.
It seems to return the last value of the relevant node:
But instead, it always returns the one before :
A very weird behavior...
Any thoughts about why it happens?
Tnx for #ShehanWisumperuma!
gameRef.keepSynced(true) was the correct answer to my issue!!!
Tnx for all of you who tried to help me!
I'm calling addValueEventListener inside the button click, but this method only reads the last item in the node. I want to read all the child value in the node What went wrong here?
btnorder.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot dataSnapshot1:dataSnapshot.getChildren())
{
SelectedItems si=dataSnapshot1.getValue(SelectedItems.class);
si.getItemname();
Toast.makeText(MyBookedItems.this, ""+si.getItemname(), Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
});
I think you can create an array list and put all snapshot data into it, and then you can find the last data of the list with the value you find by subtracting one from the length of the list. Sorry for my bad English :( I have tried to explain in the solution in the code below)
ArrayList<SelectedItems> selectedItems = new ArrayList<SelectedItems>();
for(DataSnapshot dataSnapshot1:dataSnapshot.getChildren())
{
SelectedItems si=dataSnapshot1.getValue(SelectedItems.class);
selectedItems.add(si);
}
selectedItems.get(selectedItems.size());
It's read all the values but I got the output as a Toast message, because of that I only see the last value)
Im using the Android SDK for firebase database.
In the database I have a structure where I keep the messages ordered by user, that way if I need their messages I just query by user.
myDatabase -> messages -> JonDoe
-> "You forgot your mail"
-> "Buy groceries"
-> JaneDoe
-> "Dog's birthday!"
The problem is if the user doesnt exist the listener keeps waiting forever, and I want to show "You have no messages" in that case. (For example, if I query the user "CharlesDoe" in the example above)
Is there a way to check if a reference exists before/after/during a query?
try this:
DatabaseReference root =FirebaseDatabase.getInstance().getReference();
DatabaseReference user = root.child("myDatabase").child("messages");
user.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
if (snapshot.child("CharlesDoe").exists()) {
// run some code
}else{
Toast.makeText(this,"no messages",Toast.Length_LONG).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Here it will query on node messages and then it will check if the child exists and do the required.
Try this on
DatabaseReference root =FirebaseDatabase.getInstance().getReference();
DatabaseReference user =
root.child("myDatabase").child("messages").child("CharlesDoe");
user.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
if (snapshot.exists()) {
// run some code
}else{
Toast.makeText(this,"no messages",Toast.Length_LONG).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I have a Firebase database that I want to retrieve the friend ID from. This works perfectly as I'm getting the right value when logging the friendUserId in the for loop. However, the log at the end of the method only displays the right value after executing the method twice. At first it displays "s", the second time it displays the string that I want. I feel like it has got something to do with processing time of the query, but I'm not sure really. How do I solve this?
public String friendUserId="s";
public void checkUserExistence() {
mDatabase.child("Users")
.orderByChild("username")
.equalTo(EmailSearchQuery)
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
friendUserId = childSnapshot.getKey();
Log.d("dwada",friendUserId);
}
} else
Toast.makeText(AddAFriend.this, "Gebruiker niet gevonden", Toast.LENGTH_LONG);
}
#Override
public void onCancelled(DatabaseError firebaseError) {
Log.e("MainActivity", "onCancelled", firebaseError.toException());
}
});
Log.d("dwada",friendUserId);
}
for example searching in circles for a user circle if a data exist I want it DO process 1 and if data doesn't exist I want it to create one then DO process 2 ... but what happens in this code if data doesn't exist it will create one then do process 2 then go back then do process 1 after checking. so how can I stop the listener after process 2.
sorry if the circles example is too ambiguous but this is the simplest example I could think of .
Firebase ref= new Firebase("https://XXXXX.firebaseio.com/circles/");
Query queryRef = ref.orderByChild("circalename").equalTo(user.circalename);
ValueEventListener listener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot datasnapshot) {
if (datasnapshot.exists()) { // I don't want to get back here after
//creating the data in the else statement
// DO process 1
}
// if my data doesnt exist I will create one after that STOP listening
else {
// create circle
// do process 2
}
}
What you can do is use addListenerForSingleValueEvent
as it listens to the event only once
i.e. in your case
queryRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
if (datasnapshot.exists()) {
// code if data exists
} else {
// code if data does not exists
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Despite Shubham Arora's answer is the best solution for this case, I'm going to show you how to do exactly what you asked with these two solutions that are quite simple:
1. Global boolean
Create a global boolean and change it once your condition is met:
query.addListenerForSingleValueEvent(new ValueEventListener() {
boolean processDone = false;
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists() && !processDone) {
// do process 1
} else {
// do process 2
processDone = true;
}
}
#Override public void onCancelled(DatabaseError databaseError) {}
});
2. Remove listener
Remove your listener once your condition is met:
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
// do process 1
} else {
// do process 2
query.removeEventListener(this);
}
}
#Override public void onCancelled(DatabaseError databaseError) {}
});
Both solutions did work fine for me when I was using ChildEventListener and Shubham Arora's answer couldn't help.