How to retrieve data from one single userID Firebase Android

Question

In my firebase database, I have list of users that have different information under them. I would like to retrieve information from a single userId, which I will define in the code and I want to only get information from that user.

My data looks like;

UserTable
{
  "fmXWU324VHdDb8v6h7gvNjRojnu33" : {
    "-KbJtw467nl6p253HZ537" : {
      "Name" : "name1",
      "Email" : "something1@something.com",
      "userid" : "fmXWU324VHdDb8v6h7gvNjRojnu33"
    }
  },
  "pJtC45fW0MMi352UiPWnWdIS7h88" : {
    "-Kb012ls9iMnzEL723o9I" : {
      "Name" : "name2",
      "Email" : "something2@something.com",
      "userid" : "pJtC45fW0MMi352UiPWnWdIS7h88"
    },
    "-Kb0aq0q25FJq38256SrC" : {
      "Name" : "name3",
      "Email" : "something3@something.com",
      "userid" : "pJtC45fW0MMi352UiPWnWdIS7h88"
    },
    "-Kb0atopfK64F6jy124Qi1u" : {
      "Name" : "name3",
      "Email" : "something1@something.com",
      "userid" : "pJtC45fW0MMi352UiPWnWdIS7h88"
  }
}

and I want to, say for example read and display all data from this user "fmXWU324VHdDb8v6h7gvNjRojnu33". I am not sure how I can do that. I tried this, which seems logical but it doesn't seem to work:

df.child("UserTable").child(user.getUid())).addChildEventListener(new ChildEventListener()

it gives this error:

Can't convert object of type java.lang.String to type com.android.example.UserTable

In addition, I have tried:

df.child("UsersTable").child("userid").child(user.getUid()).ad‌dChildEventListener(‌new ChildEventListener()

I can seem to figure out what I am doing wrong, as what I have tried seems logical and should work. Please can someone help me out.

EDITED:

public ArrayList<data> get(String userID){

      df.child("UsersTable").child(userID).ad‌dChildEventListener(‌new ChildEventListener()  {
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        fetch(dataSnapshot);
    }

    @Override
    public void onChildChanged(DataSnapshot dataSnapshot, String s) {
        fetch(dataSnapshot);
    }

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

    @Override
    public void onChildMoved(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

return data;

Update

private void fetchData(DataSnapshot dataSnapshot)
{

    for (DataSnapshot ds : dataSnapshot.getChildren())
    {
        Userdetail userdetail =ds.getValue(Userdetail.class);
        userdetails.add(userdetail );
    }
}

Can you please add the code within child event listener. The error seems to propagate from there — Mohammad Aasif, Jan 25 '17 at 12:50
its push Id to store entries from same user as unique. because 1 user can add multiple data under they id and I want each data to be unique and not override the previous — Josh Joe, Jan 25 '17 at 13:15
You can read more about how to work with Firebase retrieve data in the official documentation: https://firebase.google.com/docs/database/admin/retrieve-data — Francisco Durdin Garcia, Jan 25 '17 at 17:26
@FranciscoDurdinGarcia Thanks for the link. I am having 1 issue and I have search everyone but I can't seem to find a solution. I have a recylerview to which I am loading the data from Firebase, however, recylerview does not automatically show data and I have to click on a edittext to load the data. I think this might be because the layout/recylerview is not refreshing but I have tried almost everything I could find but I can't seem to fix it. Do you know a solution? — Josh Joe, Jan 25 '17 at 17:36
@JoshJoe Are you calling `notifyDataSetChanged();`after set your new values? Also, why you are not using `FirebaseRecyclerAdapter` to works with `RecyclerView` and Firebase? The API give you some support classes to implement this kind of things more easily, as `RecyclerViews` and `Lists` — Francisco Durdin Garcia, Jan 25 '17 at 17:39
@JoshJoe You can find a good example about how to use `FirebaseRecyclerAdapter` in the next question: http://stackoverflow.com/questions/36235919/how-to-use-a-firebaserecycleradapter-with-a-dynamic-reference-in-android — Francisco Durdin Garcia, Jan 25 '17 at 17:40
I didn't come across FirebaseRecyclerAdapter when I started my project and I am 70% finish if I change now I will need to change 60% of the code. Which will be a nightmare :) — Josh Joe, Jan 25 '17 at 17:44

score 1 · Accepted Answer · edited Jan 26 '17 at 06:26

1

First initialize your database like this

mDatabase= FirebaseDatabase.getInstance().getReference().child("your_node_name");

then try setting a ValueEventListener to your Database reference. Inside the onDataChange method you can retrieve your data like this

public void onDataChange(DataSnapshot dataSnapshot) {
    User user= dataSnapshot.getValue(User.class);
}

EDIT:

ValueEventListener postListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        User user= dataSnapshot.getValue(User.class);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
};
mDatabase.addValueEventListener(postListener);

edited Jan 26 '17 at 06:26

wake-0

3,918
5
28
45

answered Jan 25 '17 at 12:52

Mufad

191
1
15

Hi, sorry I am not sure how this would work because you haven't added any listener. – Josh Joe Jan 25 '17 at 13:01
Currently as my code is, I am able to retrieve data but the data is being retrieved from all users I want to only get from defined userid – Josh Joe Jan 25 '17 at 13:06
Thanks for the update, could I please check how I can retirve data only from one user (for a user which I give userid for) – Josh Joe Jan 25 '17 at 13:10
I was facing same situation with ChildEventListener, you can use a ValueEventListener in your database reference and change the reference to `mDatabase= FirebaseDatabase.getInstance().getReference().child("your_node_name").child("userID");` – Mufad Jan 25 '17 at 13:15
Do you know how I can delete specific entry from firebase, given a uId and pushID? – Josh Joe Jan 25 '17 at 14:11
You're welcome, just use `mDatabase.removeValue();` to remove the child! – Mufad Jan 25 '17 at 15:01
Also, I have my data being loaded in in recylerview from firebase. However, the recylerview does not automatically refresh and I to click an editbox to make the the appear on the app. Do you know how this can be fixed? – Josh Joe Jan 25 '17 at 16:08

Rishabh Mahatha · Answer 2 · 2017-01-25T13:20:56.260

1

  DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("UsersTable").child(FirebaseAuth.getInstance().getCurrentUser().getUid()).addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        if(dataSnapshot.exists())
        {
            for(DataSnapshot userDetails : dataSnapshot.getChildren()) {
                Log.d("valueName:", userDetails.child("Name").getValue());
                Log.d("valueEmail:", userDetails.child("Email").getValue());
                Log.d("valueuserid:", userDetails.child("userid").getValue());
            }
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

use this will solve your problem.

edited Jan 25 '17 at 13:20

answered Jan 25 '17 at 13:15

Rishabh Mahatha

1,251
9
19

Hi, I am getting this error: Can't convert object of type java.lang.String to type com.android.example.UserTable – Josh Joe Jan 25 '17 at 13:30
you are using fetch(dataSnapshot); method? – Rishabh Mahatha Jan 25 '17 at 13:32
Yes. I have a for loop in that method doing exactly this for(DataSnapshot userDetails : dataSnapshot.getChildren() – Josh Joe Jan 25 '17 at 13:33
remove the loop from your fetch(dataSnapshot); and run. – Rishabh Mahatha Jan 25 '17 at 13:37
Please see update. If i remove loop how would the data be retrieved – Josh Joe Jan 25 '17 at 13:44

score 0 · Answer 3 · answered Jan 25 '17 at 13:19

0

Add value event listener instead of child event listener.

df.child("UsersTable").child(user.getUid()).addValueEventListener(newValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
           if(dataSnapshot!=null){
             fetch(dataSnapshot);
           }
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

answered Jan 25 '17 at 13:19

Saurabh Padwekar

3,888
1
31
37

Do you know how I can delete specific entry from firebase, given a uId and pushID? – Josh Joe Jan 25 '17 at 14:11
Try this `firebaseRef.child(uid).removeValue()` – Saurabh Padwekar Jan 25 '17 at 14:21
To remove `ref.child(userid).setValue(null);` – Mohammad Aasif Jan 26 '17 at 12:51

How to retrieve data from one single userID Firebase Android

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