how to get string array from firebase realtime database

Question

Firebase Realtime database structure

databaseReference = FirebaseDatabase.getInstance().getReference("/sample");

databaseReference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        Log.d(TAG, "onDataChange: dataSnapshot "+dataSnapshot.getValue());
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {

    }
});

I'm new to android app development and firebase as well. i m fetching data from sample node and getting DataSnapshot value like below.

{size=[Small, Large, Ex-Large], type=[Type 1, Type 2], color=[Red, Green, Blue], category=[T-Shirt, Jeans, Sweater]}

need some expect help, any suggestion will greatly appreciated.

Thanks

How do you want to retrieve those values? Also which values do you want to get from the database? — PradyumanDixit
– PradyumanDixit, Commented Nov 3, 2018 at 13:27
i want to set each string array on different spinner in android. — ninja jack
– ninja jack, Commented Nov 3, 2018 at 13:28
Hey @ninjajack, if you found my answer useful, do mark it correct by clicking the V- type button next to it, this helps Stack Overflow future readers, and I'd appreciate that. Cheers! :) — PradyumanDixit
– PradyumanDixit, Commented Nov 9, 2018 at 3:20

PradyumanDixit · Accepted Answer · 2018-11-04 05:31:43Z

3

To retrieve values separately, you can use a code like this:

databaseReference.child("category").addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                   for (int i=0;i<3;i++) {
                     // category is an ArrayList you can declare above
                        category.add(dataSnapshot.child(String.valueOf(i)).getValue(String.class));

                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) { // Do something for this

                }
            });

Similarly you can add values of other nodes in your other ArrayLists, just by changing the value of Childs in this code.

edited Nov 4, 2018 at 5:31

answered Nov 3, 2018 at 13:35

PradyumanDixit

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6 Comments

PradyumanDixit Over a year ago

@ninjaJack, can you try the above code and tell what gets stored in category arraylist ?

ninja jack Over a year ago

its working i did bit change category.add(dataSnapshot.child(String.valueOf(i)).getValue(String.class));

PradyumanDixit Over a year ago

Great, you can use similar code for other parts of your problem. Also, consider marking the answer as correct, I'd appreciate that. Cheers! :)

ninja jack Over a year ago

but what if i want to get all string arrays at a same time..and thanks a lot for help :D

PradyumanDixit Over a year ago

@ninjajack ah, my bad for String.valueOf(i), great you spotted that :)

|

Sergio94 · Accepted Answer · 2019-03-24 20:47:23Z

2

Firebase has no native support for arrays. If you store an array, it really gets stored as an "object" with integers as the key names.

// we send this

['hello', 'world']

// Firebase stores this

{0: 'hello', 1: 'world'}

Best Practices: Arrays in Firebase

// TRY THIS

@Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            youNameArray = new ArrayList<>();

            for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                String data = snapshot.getValue(String.class);
                youNameArray.add(data);
            }
            Log.v("asdf", "First data : " + youNameArray.get(0));
        }

answered Mar 24, 2019 at 20:47

Sergio94

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Comments

Frank van Puffelen · Accepted Answer · 2018-11-03 23:29:25Z

Something like this:

databaseReference = FirebaseDatabase.getInstance().getReference("/sample");

databaseReference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        for (DataSnapshot sampleSnapshot: dataSnapshot.getChildren()) {
            Log.d(TAG, "onDataChange: sampleSnapshot "+sampleSnapshot.getKey()+" = "+sampleSnapshot.getValue());
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        throw databaseError.toException(); // don't ignore errors
    }
});

The difference is that in my answer I loop over dataSnapshot.getChildren() to get each individual sample snapshot. The sampleSnapshot.getValue() call should return a List.

Satan Pandeya · Accepted Answer · 2020-07-04 06:10:05Z

FirebaseDatabase database = FirebaseDatabase.getInstance();     
    
    DatabaseReference refence = database.getReference();
    


    refence.addValueEventListener(new ValueEventListener()
            {

                @Override
                public void onDataChange(DataSnapshot snapshot) {
                    // TODO Auto-generated method stub
                    
                    ArrayList array= new ArrayList<>();
                    
                    
                       for (DataSnapshot ds : snapshot.getChildren()){
                            
                           String data = ds.getValue().toString();
                           
                            array.add(data);
                                                        
                         
                            
                           

                            
                        }

                       System.out.println(array); 
                    
                }

                @Override
                public void onCancelled(DatabaseError error) {
                    // TODO Auto-generated method stub
                    
                }
        
            });

In my case String.class does not work instead .toString method works

String data = ds.getValue().toString();

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