I am using the following to fetch a username from Firebase. But in this case, how do I get to know, if the username exists or not.
Firebase firebaseRef = new Firebase("<Firebasae_URL>/Users");
Query query=firebaseRef.orderByChild("username").equalTo("username");
So in your case the code should be like this, to find an username exists in your database.
Firebase firebaseRef = new Firebase("<Firebasae_URL>/Users").child("username");
firebaseRef.addListenerForSingleValueEvent(new ValueEventListener) {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
// User Exists
}
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});
The solution I found to check if a query return value was
let docRef = db.collection('videos').select('id').where('id','==',quoteData.id);
docRef.get().then(function(doc){
if(doc.size > 0){
// return value
}
else{
// no return value
}
})
Related
I've tried so many ways to check if a user id is already in the firebase but all method are in vain.
Below is my code to check if user id exists but whatever data I enter it does not show the required error.
userid = findViewById(R.id.userid);
String userVal = userid.getEditText(). getText().toString();
boolean userquery = FirebaseDatabase.getInstance().getReference().child("user").orderByChild("userid").equals(userVal);
if(userquery) {
userid.setError("This user name already exists");
return;
}
Whenever I try to add existing value in the input it accepts the value and overwrites in the database.
Here is the screenshot of my firebase database.
Your code so far only sets up a query. It doesn't actually execute the query, so there's no way it can detect whether the data exists. To execute a query, you have to attach a listener to it.
So in your case, that could be something like:
boolean userquery = FirebaseDatabase.getInstance().getReference().child("user").orderByChild("userid").equals(userVal);
userquery.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
#Override
public void onComplete(#NonNull Task<DataSnapshot> task) {
if (!task.isSuccessful()) {
Log.e("firebase", "Error getting data", task.getException());
}
else if (task.getResult().exists()) {
userid.setError("This user name already exists");
}
}
});
On older SDK versions the equivalent would be:
boolean userquery = FirebaseDatabase.getInstance().getReference().child("user").orderByChild("userid").equals(userVal);
userquery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
userid.setError("This user name already exists");
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
}
I am making an android app through android studio in java language. I have linked it to firebase Realtime database. There are auto generated push IDs as the last child. I want to retrieve my database values back in an activity. I am facing problem in giving reference to the push IDs.
This is what I have tried.
myRef = myfire.getReference().child("Data").child(strUID).child("Traffic").child("Wedding");
final String uid =myRef.getKey();
myRef.child(uid).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() == null) {
Toast.makeText(getApplicationContext(),"Data Not Available",Toast.LENGTH_LONG).show();
} else {
String stData1 = (Objects.requireNonNull(dataSnapshot.child("stData1").getValue())).toString();
String stData2 = (Objects.requireNonNull(dataSnapshot.child("stData2").getValue())).toString();
String stData3 = (Objects.requireNonNull(dataSnapshot.child("stData3").getValue())).toString();
String stData4 = (Objects.requireNonNull(dataSnapshot.child("stData4").getValue())).toString();
category basic = new category(stData1,stData2,stData3,stData4);
tvBalance.setText(stData4);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
Please provide a practical example.
Edit
This is my database structure:------------
Data>>
user id>>>>
Traffic>>>>
Wedding>>>>
Auto ID>>>
>stData1
>stData2
>stData3
>stData4 //I want to get this last value//
my json file
{
"Data" : {
"UyhzVqsz1BVFKoePa2NEmlPFu382" : {
"Traffic" : {
"Wedding" : {
"-MYKeSN8GZ8WbI-8TfVB" : {
"stData1" : "15 Apr 2021,06:43:00:pm",
"stData2" : "Wedding",
"stData3" : "kkk",
"stData4" : "100"
}
}
}
}
}
}
The only ways to get a node is by either knowing its full path, or by knowing the path to the parent node, and then some unique value under the node. Neither seems to be the case for the stData4 in your JSON, so you'll have to load the entire Wedding node and then loop over the results to get the part you want.
This isn't too bad though:
myRef = myfire.getReference("Data").child(strUID).child("Traffic/Wedding");
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (!dataSnapshot.exists()) {
Toast.makeText(getApplicationContext(),"Data Not Available",Toast.LENGTH_LONG).show();
} else {
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
String stData1 = childSnapshot.child("stData1").getValue(String.class);
String stData2 = childSnapshot.child("stData2").getValue(String.class);
String stData3 = childSnapshot.child("stData3").getValue(String.class);
String stData4 = childSnapshot.child("stData4").getValue(String.class);
}
category basic = new category(stData1,stData2,stData3,stData4);
tvBalance.setText(stData4);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
The code above assumes that:
strUID has the value UyhzVqsz1BVFKoePa2NEmlPFu382
I am making an app based on firebase Realtime database. I have set rules as given below:
{
// Allow anyone to read data, but only authenticated content owners can
// make changes to their data
"rules": {
"Users": {
"$uid": {
".read": true,
// or ".read": "auth.uid != null" for only authenticated users
".write": "auth.uid == $uid"
}
}
}
}
I am trying to add data by the following code in java. But getting Error.
myfire = FirebaseDatabase.getInstance();
myRef = myfire.getReference("Users").child("Some Authentic User");
//======================
btnAdmit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
stName = etName.getText().toString();
stRoll = etRoll.getText().toString();
etName.setText("");
etRoll.setText("");
myRef = myfire.getReference();
myRef.child("201").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
model model =new model();
model.setFb01name(stName);
model.setFb04roll(stRoll);
myRef.child("Basic").setValue(model);
Toast.makeText(getApplicationContext (),"Sorry",Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Toast.makeText(getApplicationContext (),"Error",Toast.LENGTH_SHORT).show();
}
});
}
});
My model class goes like this:
public class model {
String fb01name;
String fb04roll;
public model() {
}
public model(String fb01name, String fb04roll) {
this.fb01name = fb01name;
this.fb04roll = fb04roll;
}
public String getFb01name() {
return fb01name;
}
public void setFb01name(String fb01name) {
this.fb01name = fb01name;
}
public String getFb04roll() {
return fb04roll;
}
public void setFb04roll(String fb04roll) {
this.fb04roll = fb04roll;
}
}
I cannot find the error. The logcat is blank.
I was successful in adding data previously .But after changing the rules it failed.I want the database path like this:
(Main Node)Users--
(first Child)---Authenitic User(As added by "Add User")
(second child)-----some id( like '201')
(Targeted Children) 1 ------fb01name (and its value)
2------fb04roll (and its value)
Can anybody will please guide me practically?
Since onCancelled is called on your listener, that means that you don't have permission to read the data that you're trying to access. If you log the databaseError.toException() that you get in onCancelled you should also see that, as it should tell you that permission was denied.
Distilling your code down, you're attaching a listener to:
myRef = myfire.getReference();
myRef.child("201").addValueEventListener(...
So that is the path /201 in the database, where indeed your rules don't grant anyone read access.
My best guess is that the myRef = myfire.getReference(); line is a mistake, and removing it will lead to reading /Users/Some Authentic User/201, which is probably what you want to do.
I am working with firebase database and i was trying to get the value of a child using this code below and may System.out.println(MyCredit.toString()); is always returns null: Please see my firebase database
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Users");
ref.addListenerForSingleValueEvent(
new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
//Get map of users in datasnapshot
CollectCredits((Map<String,Object>) dataSnapshot.getValue());
}
#Override
public void onCancelled(DatabaseError databaseError) {
//handle databaseError
}
});
private void CollectCredits(Map<String,Object> users) {
MyCredit = new ArrayList<>();
//iterate through each user, ignoring their UID
for (Map.Entry<String, Object> entry : users.entrySet()){
//Get user map
Map singleUser = (Map) entry.getValue();
//Get Credit field and append to list
MyCredit.add((Long) singleUser.get("Credit"));
Toast.makeText(MainActivityCustonlistViewnew.this, "Credit : " +String.valueOf(MyCredit), Toast.LENGTH_SHORT).show();
}
System.out.println(MyCredit.toString());
}
Try this:
private void CollectCredits(DataSnapshot dataSnapshot) {
MyCredit = new ArrayList<>();
//iterate through each dataSnapshot
for (DataSnapshot d1 : dataSnapshot.getChildren()){
MyCredit.add(d1.getValue());
}
}
Let me give you some suggestions, Try to check your firebase database path both the root and child path because some time you did everything correctly but the path you specified to your Database reference which is not referring to the correct path. So it can produce the same result what are getting right now.
Below is my firebase data.
users
a81b0dec-671e-4840-9977-e932274928fb
email: "s#s.com"
screenname: "SSS"
totalmoney: "0"
uid: "a81b0dec-671e-4840-9977-e932274928fb"
c934beeb-51d2-4919-bff0-64153abff1dd
email: "p#p.com"
screenname: "PPP"
totalmoney: "0"
uid: "c934beeb-51d2-4919-bff0-64153abff1dd"
e0187af9-20a9-4088-a86c-7fb8cf3b4d47
email: "o#o.com"
screenname: "OOO"
totalmoney: "0"
uid: "e0187af9-20a9-4088-a86c-7fb8cf3b4d47"
How can I retrieve the node with uid = "a81b0dec-671e-4840-9977-e932274928fb".
Here's what I have tried so far, but it's not working.
String uid = "a81b0dec-671e-4840-9977-e932274928fb";
Query query = fb.orderByChild("uid").equalTo(uid);
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot data) {
// TODO Auto-generated method stub
Log.i("SINGLE VALUE EVENT", data.toString());
}
#Override
public void onCancelled(FirebaseError error) {
// TODO Auto-generated method stub
}
});
Your current code executes a query. Since a query can match multiple child nodes, it returns a list of values. Even when there is only one matching result, it returns a list of one.
You can handle this in your code by iterating through the children:
public void onDataChange(DataSnapshot data) {
for (DataSnapshot userSnap: data.getChildren) {
Log.i("SINGLE VALUE EVENT", userSnap.child("email").getValue(String.class));
}
}
But in this case you don't even need a query, since you've (wisely) also stored the users under their uid. That means you can directly access the user by that uid, which saves some code and will be faster:
String uid = "a81b0dec-671e-4840-9977-e932274928fb";
DatabaseReference user = fb.child(uid);
user.addListenerForSingleValueEvent(new ValueEventListener() {
public void onDataChange(DataSnapshot data) {
Log.i("SINGLE VALUE EVENT", data.child("email").getValue(String.class));
}
public void onCancelled(FirebaseError error) {
Log.e(TAG, error);
}
});
You shouldn't duplicate the id, instead use:
ref.orderByKey().equalTo()
You can find what you are searching for there:
https://www.firebase.com/docs/android/guide/retrieving-data.html
To make your code more dynamic..you could declare a string for getting the uid values
EditText edt = (EditText)findViewById(R.id.editText);
String edtText = edt.getText().toString().trim();
String uid = edtText;
DatabaseReference db = fb.child(uid);
db.addListenerForSingleValueEvent(new ValueEventListener() {
public void onDataChange(DataSnapshot snapshot) {
Toast.makeText(this, "Email for supplied user is : " + snapshot.child("email").getValue(String.class), Toast.LENGTH_SHORT).show();
}
public void onCancelled(FirebaseError error) {
Toast.makeText(this,"Error as a result of " + error.getMessage(), Toast.LENGTH_SHORT).show();
}
});
If you know for sure that you're expecting only one entry (in this case since every record has a unique id), using psudo code I'd say, retrieve the 0 index of returned data.