Getting child values from firebase to android app

Question

I am having issues getting my .child items which are on my firebase displaying on my listview on my android application.

When I use the following code:

String value = dataSnapshot.child("messages").getValue(String.class);
            list.add(value);
            adapter.notifyDataSetChanged();

I am able to retrieve the data, but when a change is made to the firebase, all the data is removed and it displays the new entry.

I want to be able to retrieve .child entries from the database for example

fDatabase.child("messages").child("message").addChildEventListener(new ChildEventListener()

I would only want it to display, update and change the child messages.

Can somebody help me out, the connection to database is fine, the app is not crashing. just disconnecting due to inactivity.

Could this be a permissions thing on firebase?

My firebase rules are currently set public which i am aware off

{
  "rules": {
    "messages":{
    ".read": true,
    ".write":true,  
}
}
  }

Any advice ?

My code

public class MainActivity extends AppCompatActivity {
DatabaseReference fDatabase;
ListView listview;
ArrayList<String> list = new ArrayList<>();
ArrayAdapter <String> adapter;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listview = (ListView) findViewById(R.id.listview);
    adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, list);
    listview.setAdapter(adapter);


    fDatabase = FirebaseDatabase.getInstance().getReference();


    fDatabase.child("messages").child("message").addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            String value = dataSnapshot.child("messages").getValue(String.class);
            adapter.add((String)dataSnapshot.child("messages").getValue());
            list.add(value);
            adapter.notifyDataSetChanged();

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {
            adapter.clear();
            adapter.add((String)dataSnapshot.child("messages").getValue());
            String value = dataSnapshot.child("messages").getValue(String.class);
            list.add(value);
            adapter.notifyDataSetChanged();

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {


        }

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

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}
}

I have looked at this question but cant get it working either

Get child ID from Firebase android

When i change my code to event listener, i get back null : null : null

 protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listview = (ListView) findViewById(R.id.listview);
    adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line);
    listview.setAdapter(adapter);


    fDatabase = FirebaseDatabase.getInstance().getReference();


    fDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot messageSnapshot : dataSnapshot.getChildren()) {
                adapter.clear();
                String temp = (String) messageSnapshot.child("temp").getValue();
                String humi = (String) messageSnapshot.child("humi").getValue();
                String status = (String) messageSnapshot.child("status").getValue();
                adapter.add(humi + " : " + temp + " : " + status);
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }

Database structure

jmproject-*****
 humi: "77"
 status: "true"
 temp: "24c"

Database rules

{
  "rules": {
    ".read": true,
    ".write":true,  
}
}

check this library provided by firebase. [Using FirebaseUI to Populate a ListView](https://github.com/firebase/FirebaseUI-Android/blob/master/database/README.md#using-firebaseui-to-populate-a-listview) — Saurabh, Jan 17 '17 at 09:54

score 0 · Answer 1 · answered Jan 17 '17 at 10:30

0

You are overwriting your data under the message child. What you are looking for is dataSnapshot.getChildren(), which will return a list of all children. The issue with your implementation is you are storing just on child under the "message" key. If you want to store multiple values you need to change the key each time you store a message.

If you want to generate key automatically you can use this

String key = firebaseRef.child("messages").push().getKey();

This will create a new unique entry under the /messages/ path. Then you can save your data using this key.

answered Jan 17 '17 at 10:30

Andrej Jurkin

2,216
10
19

But using getChildren will not work with my String, is there another option ? – Joseph Jay May Jan 17 '17 at 10:59
I have changed my code now, im getting the result back as null : null : null, i have updated the question – Joseph Jay May Jan 17 '17 at 11:34
You need to add your database structure from firebase. Otherwise i can not help you. – Andrej Jurkin Jan 17 '17 at 11:53
I have added the structure from firebase. – Joseph Jay May Jan 17 '17 at 12:02

score 0 · Answer 2 · answered Aug 19 '17 at 17:57

I think the problem is that you are setting adapter in oncrete method and not in onChildAdded and onChildChanged methods. You should place the listView.setAdapter(adapter) in the childEventListener methods try it. And also your code in ChildAdded and ChildChanged is redundant. Place the code in a method and call the method from your event Listener methods.

Getting child values from firebase to android app

2 Answers2