How do I search for users based on their usernames? I have looked at numerous SO posts on this matter but am still unable to achieve what I want to do.. I have tried to apply what I saw in those posts and is shown below:
DatabaseReference usersRef = FirebaseDatabase.getInstance().getReference("users");
usersRef.orderByChild("username")
.startAt(queryText)
.endAt(queryText+"\uf8ff");
usersRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
searchList = new ArrayList<>();
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
User user = postSnapshot.getValue(User.class);
Log.d("USER: ", "" + user.getUsername());
searchList.add(user);
}
adapter = new UserCardAdapter(getContext(), searchList);
recyclerView.setAdapter(adapter);
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.e("onQueryTextChange: " ,databaseError.getMessage());
}
});
However, all users are still retrieved. I have seen the usage of startAt() and endAt() supposedly work for others on other posts but I cannot manage to get it to work for me..
This is how the user data is stored:
User Data Structure
You almost done right but you should add addListenerForSingleValueEvent after the database reference that already apply orderBy() , startAt(), endAt() like this.
usersRef.orderByChild("username")
.startAt(queryText)
.endAt(queryText+"\uf8ff")
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
searchList = new ArrayList<>();
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
User user = postSnapshot.getValue(User.class);
Log.d("USER: ", "" + user.getUsername());
searchList.add(user);
}
adapter = new UserCardAdapter(getContext(), searchList);
recyclerView.setAdapter(adapter);
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.e("onQueryTextChange: " ,databaseError.getMessage());
}
});
Your use of orderBy(), startAt(), and endAt() is correct according to the documentation.
But the addListener method must be applied directly to the object returned by the chain of orderByChild(), startAt(), and endAt() methods, and not in a new statement on the DatabaseReference retrieved with ... .getReference("users").
If you use a ChildEventListener:
DatabaseReference usersRef = FirebaseDatabase.getInstance().getReference("users");
usersRef.orderByChild("username")
.startAt(queryText)
.endAt(queryText+"\uf8ff");
.addChildEventListener(new ChildEventListener() {
List<User> searchList = new ArrayList<>();
#Override public void onChildAdded(DataSnapshot dataSnapshot, String s) {
User user = dataSnapshot.getValue(User.class);
Log.d("USER: ", "" + user.getUsername());
searchList.add(user);
}
#Override public void onChildChanged(DataSnapshot dataSnapshot, String s) {}
#Override public void onChildRemoved(DataSnapshot dataSnapshot) {}
#Override public void onChildMoved(DataSnapshot dataSnapshot, String s) {}
#Override public void onCancelled(DatabaseError databaseError) {}
});
Related
how can filter the value in firebase?
if I want to filter the value in firebase
Because the country values is variable, how can I do?
Below is my code
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Posts");
Could I filter the values?
Should I
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Posts").child("country"); //???
=====================Update===================
now, I used this code, but I don't know why I can't get the country value in readPost function. Do I miss something?
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
DatabaseReference country_ref = FirebaseDatabase.getInstance().getReference("Users").child(firebaseUser.getUid());
country_ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
country = snapshot.child("country").getValue().toString();
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
private void readPosts(){
final ProgressDialog progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Loading...");
progressDialog.show();
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Posts");
Query query = reference.orderByChild("country").equalTo(country);
query.addListenerForSingleValueEvent(new ValueEventListener() {
I can get the country value in country = snapshot.child("country").getValue().toString();
but can't get in readPost function
Queries in Firebase are done like this:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Posts")
Query query = reference.orderByChild("country").equalTo("Australia");
You can then read the values matching this query with:
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
Log.d("Firebase", userSnapshot.getKey();
Log.d("Firebase", userSnapshot.child("country").getValue(String.class);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
})
Also see the Firebase documentation on ordering and filtering data and listening to value events for lists. If you're new to Firebase, I also strongly recommend taking the codelab for Android developers.
To get all countries of "Posts"-
private ArrayList<String> countryNameList;
private String countryName;
private TextView countryNameView;
final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Posts");
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
countryName = ds.child("country").getValue().toString();
countryNameList.add(countryName);
StringBuilder stringBuilder = new StringBuilder();
for (String s : countryNameList) {
stringBuilder.append(s + "\n");
}
countryNameView.setText(stringBuilder.toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.w("TAG", "onCancelled", databaseError.toException());
}
});
I have a problem regarding querying the firebase database using a value and getting the specific node. My schema is shown here:
In my schema 'workLocations' belongs to an 'excavationWorks', and 'excavationWorks' belongs to an 'excavationLists'.
That means that the path to a specific workLocation is excavationLists/excavationWorks/workLocations/(specific workLocation)
The problem that I have is that I want to query the workLocations node by the location value (let's say London) and get the parent node (the red circled key which is the key of the specific workLocation).
I have search and read many posts but I haven't managed to make it work.
My code looks like this:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
Query query = reference.child("workLocations").orderByChild("location").equalTo("London");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot workLoc : dataSnapshot.getChildren()) {
// do something with the individual "issues"
Log.d(TAG, workLoc.getKey());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Thank you
To achieve this, you need to query your database twice like this:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
DatabaseReference workLocationsRef = reference
.child("excavationLists")
.child("excavationWorks")
.child("workLocations");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot dSnapshot : dataSnapshot.getChildren()) {
for(DataSnapshot ds : dSnapshot.getChildren()) {
String key = ds.getKey();
Query query = workLocationsRef.child(key).orderByChild("location").equalTo("London");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
String description = snapshot.child("description").getValue(String.class);
Log.d("description", description);
String partentKey = snapshot.getRef().getParent().getKey();
Log.d("partentKey", partentKey);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
query.addListenerForSingleValueEvent(eventListener);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
workLocationsRef.addListenerForSingleValueEvent(valueEventListener);
I want to get particular value using from DataSnapshot.
I am attaching the screenshot here so kindly check and help me to get particular value from Realtime Database.
Actually I am implementing chat application in which I want to get value of user from group_list.
Here is my code.
private void loadTotalGroupList() {
referenceMainUrl = FirebaseDatabase.getInstance().getReferenceFromUrl("https://pure-coda-174710.firebaseio.com");
referenceGroupList = referenceMainUrl.child("group_list");
//Check if child is available or not.
referenceGroupList.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
Log.e("dataSnapshot"," ==>"+dataSnapshot);
Map<String, Object> newPost = (Map<String, Object>) dataSnapshot.getValue();
Log.e("newPost"," ==>"+newPost);
Log.e("user: ","==>" + newPost.get("user")); // Here I am getting null value
} else {
Log.e("Child not found", " >>>");
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
and log showing like this. DataSnapshot { key = group_list, value = {First Group={-KtBH9gnTszNxcXjNu9A={message=assaasas, user=sakib}}} }
I have resolved my issue by using addChildEventListener
referenceGroupList.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String prevChildKey) {
Log.e("dataSnapshot KEY", " ==>" + dataSnapshot.getKey());
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String prevChildKey) {
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String prevChildKey) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Here dataSnapshot.getKey() returns all sub child of it.
You're listening to the location /group_list in your code. That means a a snapshot from that location will contain the following:
/First Group
/-KtBH9gnTszNxcXjNu9A
message = "..."
user = "..."
If you want to get the user value from that location, you'll have to dig into it using each intermediate path:
dataSnapshot.child("First Group").child("-KtBH9gnTszNxcXjNu9A").child("user").getValue()
Or more simply:
dataSnapshot.child("First Group"/-KtBH9gnTszNxcXjNu9A/user").getValue()
You can't skip the middle paths in the snapshot. Alternatively, you may want to listen to a location closer to the value you want:
referenceMainUrl.child("group_list/First Group/-KtBH9gnTszNxcXjNu9A");
This code runs in a loop and gives you values for all the 'user's
DatabaseReference dRef = FirebaseDatabase.getInstance().getReference().child("group_list").child("First_Group");
dRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot snapshot : dataSnapshot.getChildren()){
String userName = snapshot.child("user").getValue(String.class);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I am using firebase auth ui in order to create users with mail and password but after the registration I forward them to a new activity in order to choose I username which needs to be unique. My idea was to search the whole DB in order to see if that username exists already or not. Here is how I am trying to do this but no luck till now:
submitBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d("UserName", "Click: ");
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference("USERS");
mDatabase.orderByChild("username").equalTo("name1").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot: dataSnapshot.getChildren()) {
//Here you can get all data
Log.d("UserName", "onDataChange: "+snapshot.toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
I have also tried this one:
submitBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d("UserName", "Click: ");
DatabaseReference mFirebaseDatabaseReference = FirebaseDatabase.getInstance().getReference();
Query query = mFirebaseDatabaseReference.child("USERS").orderByChild("username").equalTo("name1");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
//TODO get the data here
Log.d("UserName", "onDataChange: " + dataSnapshot.toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
};
query.addValueEventListener(valueEventListener);
}
});
The only reason your code is not working is because "username" is not a direct child of the USERS table.
Your direct children will have random ids , which you can iterate trough with ChildEventListener like this:
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference("USERS");
mDatabase.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String previousChildName) {
User user = dataSnapshot.getValue(User.class); // pojo
if(user.getUsername().equals("name1") {
// do something
}
}
...
)
I am having a hard time with figuring out how to query my Firebase database. Here is what it looks like.
And here is my code:
//RETRIEVE
public ArrayList<Spacecraft> retrieve()
{
String myUserId = acct.getId();
//db.addChildEventListener(new ChildEventListener() {
db.child("/users/uid").equals(myUserId)
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//fetchData(dataSnapshot);
fetchData(dataSnapshot);
adapter.notifyDataSetChanged();
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
fetchData(dataSnapshot);
adapter.notifyDataSetChanged();
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return spacecrafts;
}
So db.addChildEventListener will retrieve the entire database. But what I want is to only retrieve data for users whose uid is equal to String myUserId. And I want to sort in ascending order by Level. I have read the docs and watched videos but I cannot figure it out. Any help would be appreciated.
Query query = db.child("users").orderByChild("uid").equalTo("myUserId");
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
for (DataSnapshot userSnapshot: snapshot.getChildren()) {
System.out.println("User "+userSnapshot.child("uid").getValue());
}
}
...
But if you're frequently accessing the data by UID, you're off restructuring your database to store all users under their own UID:
users
myUserId
Level: 2
NumCorrect: 8
You can then read the data with:
db.child("users/myUserId").addValueEventListener(new ValueEventListener() {
public void onDataChange(DataSnapshot snapshot) {
fetchData(dataSnapshot);
}
For more on Firebase queries, see the Firebase documentation on sorting and filtering data. Since you're new to NoSQL, I also recommend reading NoSQL data modeling and viewing Firebase for SQL developers.
You can reverse the array list
ArrayList<UserModel> user_list = new ArrayList<>();
for (DataSnapshot snapshot :dataSnapshot.getChildren()) {
UserModel userModel = snapshot.getValue(UserModel.class);
user_list.add(userModel);
Collections.reverse(user_list);
}