I am new to Firebase and Android. I have stored user authentication details (name, profile image other than email ID) in my Firebase account. I want to retrieve those data (such as names etc.,) to the other part of my app. How can I retrieve my realtime database child values?
final FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("userID").child("displayName");
// Attach a listener to read the data at our posts reference
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String displayName = dataSnapshot.getValue().toString();
System.out.println(displayName );
}
For more:
Read and Write Data on Android - Firebase Documentation
If you want to get the names of all the users, then you can do it like this
DatabaseReference mRef = FirebaseDatabase.getInstance().getReference();
mRef.child("users").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot snapshot: dataSnapshot.getChildren()){
Log.v("user_name", snapshot.getValue(String.class));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Related
I want to read data from my Firebase database for all questions. For e.g. for question1 I want to store ques,ans and answeredBy into three variables. What I am currently doing is here.
private FirebaseDatabase database=FirebaseDatabase.getInstance();
private DatabaseReference
quizRef=database.getReference("Quiz").child("Questions");
quizRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds:dataSnapshot.getChildren())
{
ModelClass modelClass=new ModelClass();
modelClass.setQues(ds.child("question1").getValue(ModelClass.class).getQues());
modelClass.setAns(ds.child("question1").getValue(ModelClass.class).getAns());
textViewQuestionText.setText(modelClass.getQues());
}
}
#Override
public void onCancelled(DatabaseError error) {
textViewQuestionText.setText("Error occurred");
}
});
Tried and Tested. You dont have to check for keys like question1,question2 etc
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference reference = database.getReference("Quiz/Questions");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds: dataSnapshot.getChildren()) {
ModelClass modelClass = (ds.getValue(ModelClass.class));
modelClass.getAns();
modelClass.getQes();
// fetch any key value pair
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I recommend to use firebase generated hash keys instead of your own keys like question1,question2 etc
Check this
You can just use the data from your Firebase Database directly using the following code:
DatabaseReference q1Ref = quizRef.child("question1");
q1Ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String question = dataSnapshot.child("ques").getValue(String.class);
String answer = dataSnapshot.child("ans").getValue(String.class);
int ansBy = dataSnapshot.child("answeredBy").getValue(Integer.class);
// now you can do what you want with the values stored in the variables
}
#Override
public void onCancelled(DatabaseError error) {
textViewQuestionText.setText("Error occurred");
}
});
To read or write data from the database, you need an instance of DatabaseReference:
private DatabaseReference mDatabase;
// ...
mDatabase = FirebaseDatabase.getInstance().getReference();
To read data at a path and listen for changes, use the addValueEventListener() or addListenerForSingleValueEvent() method to add a ValueEventListener to a DatabaseReference.
You can use the onDataChange() method to read a static snapshot of the contents at a given path, as they existed at the time of the event.
For more information you can refer to firebase docs
I have a Firebase database of the following:
Root Node
User node
an automatically generated key generated by ref.push()
attributes
I am trying to retrieve only one of the attributes of a single child under the user. Here is a screenshot of my database:
Screenshot of my database
If you check the screenshot, i only want to retrieve email (assume i have no other way of getting it). However, in the code, I wouldn't know the child of User that contains the email I want. This is what i am currently doing but it is very inefficient (this code checks if my current user exists, if not, it adds his/her data to the database):
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("User");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Iterable<DataSnapshot> children = dataSnapshot.getChildren();
for (DataSnapshot child:children) {
User user1 = child.getValue(User.class);
Log.d("kharas email",user1.getEmail()+"");
if(!user1.getEmail().equals(firebaseAuth.getCurrentUser().getEmail())){
GraphRequest.newMeRequest(token, new GraphRequest.GraphJSONObjectCallback() {
String birthday = "Not Available";
#Override
public void onCompleted(JSONObject object, GraphResponse response) {
User userInfo = new User();
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("User");
birthday = object.has("email")+"";
userInfo.setBirthday(birthday);
userInfo.setEmail(firebaseAuth.getCurrentUser().getEmail());
ref.push().setValue(userInfo);
}
}).executeAsync();
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I tried to set the child under User to the email but firebase wouldnt let me use some special characters in the key. Any suggestions to make the code more efficient would be appreciated. Or any key suggestions that would make querying easier would be great.
Thanks in advance
Instead of putting random value or auto generated key you can add user's id which is received from fire base
firebaseAuth.getCurrentUser().getUid()
This will be more easy to access and will be more efficient because whenever you get will logged in, you will have this user_id and corresponding to user_id you can get email instead of checking all values in database
The only way to retrieve email if you dont know the random key is this:
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("User");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot datas: dataSnapshot.getChildren()){ for (DataSnapshot child:children) {
String email=datas.child("email").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Or you can use firebase authentication and add the userid under Users instead of push() then retrieve the userid :
FirebaseUser user=FirebaseAuth.getInstance().getCurrentUser();
String userid=user.getUid();
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("User");
ref.child(userid).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String email=dataSnapshot.child("email").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
That way you do not have to loop.
I want to access article information but the problem I face is Article array names are some random keys and not like the one given here.
To access the keys inside the Article node, do the following:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = rootRef.child("Branch").child("Users");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot datas: dataSnapshot.getChildren()){
String key=datas.child("keys").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Here the datasnapshot is Users you then iterate inside the random keys and get the values(keys) that are inside the Articles.
i want to retrieve the rates in the firebase database and store it in an String, can anyone suggest me how to take the values alone from the database. i used this code and cannot get any values.i have added my database image for reference
DatabaseReference rootRef = FirebaseDatabase.getInstance().
getReference("fish-market-ukkadam");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String rates = ds.getValue(String.class);
Log.d("TAG", rates);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
};
rootRef.addListenerForSingleValueEvent(eventListener);
MY DATABASE IMAGE
Replace this:
FirebaseDatabase.getInstance().getReference("fish-market-ukkadam");
With this:
FirebaseDatabase.getInstance().getReference();
Your database project name is "fish-market-ukkadam", but that is not the name of the root node that you can access by name.
I have integrated Google sign-in in my app and i am pushing some data in to fire base including user U-id.I had researched a lot and didn't get anything the problem i am facing that i want to fetch Particular data for eg If User A sign-in and push 5 data and Then User B sign-in and push 3 data.I want a query like if User A sing-in Again it will get his 5 data only and not the data which is pushed by User B.Thanks in Advance :)
By using this it fetch all the data from firebase:
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
FirebaseModel firebasemodel =
data.getValue(FirebaseModel.class);
firebasemodels.add(firebasemodel);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
I have tried all that .child .orderby and .equalTo but did'nt work
My Structure is Like:
My FireBase Structure
You also need a reference to the data, which isn't included in your code block. So something along the lines of (this should be before this):
DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("notepad-secure/notepad");
Firstly add a user_id key in your child data, it will look like below :
id:"",
note:"",
title:"",
user:""
user_id:"{id from which user have you uploaded data}"
And than you can call below function with specific user data like
below Note : "user_id" = id from which user have you uploaded data
DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
Query query = reference.child("notepad").orderByChild("id").equalTo("user_id");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
// dataSnapshot is the "notepad" node with all children with id
for (DataSnapshot notepad: dataSnapshot.getChildren()) {
// do something with the individual "notepad_data"
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
To Fetch Particular values from the firebase,try this code
FirebaseDatabase database;
database.getReference().child("notepad-secure").orderByChild("id").equalTo(user).addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() != null) {
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
User userdet =childSnapshot.getValue(yourclass.class);
String note=userdet.note;
//Here you will get the string values what you want to fetch
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
First U have to differentiate.U have to implement Firebase Authentication the u can get Firebase UID of every USER.
String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();
Then store seperatly in new node.
i.e Take Firebase Database Instance and
databaserefernace.child("Data").Child("userID);
When your add a user data to Firebase database, you can add it using the specific uid provided by the FirebaseAuth object like this:
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
Assuming you that your database strucure look like this: Firebase root -> notepad-secure -> notepad, to retrieve data, you can use this code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference notepadRef = rootRef.child("notepad-secure").child("notepad").child(uid);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String id = dataSnapshot.child("id").getValue(String.class);
String note = dataSnapshot.child("note").getValue(String.class);
String title = dataSnapshot.child("title").getValue(String.class);
String user = dataSnapshot.child("user").getValue(String.class);
Log.d("TAG", id + " / " + note + " / " + title + " / " + user);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
notepadRef.addListenerForSingleValueEvent(eventListener);