Clever Geek Handbook

Firebase Database DataSnapshot Filter for Kids on Android

I want to request data from Firebase on Android. And this is my datamy data

And this is my Android Studio code:

Firebase myFirebaseRef = new Firebase("https://....../myCoffee/"+phone+"");
            myFirebaseRef.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot snapshot) {
                    int size= (int) snapshot.getChildrenCount();
                    txtMyCoffee.setText(""+size);
                          }
                @Override
                public void onCancelled(FirebaseError firebaseError) {
                }
            });

Question: The total number of children is 4. How can I filter children just to include children whose "coffeeNo" is "Acoffee"?

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3 answers


Just improve your query to only get the result you are looking for:

DatabaseReference databaseRef = FirebaseDatabase.getInstance().getReferenceFromUrl("https://....../myCoffee/"+phone+"");
Query acoffeeQuery = databaseRef.orderByChild("coffeeNo").equalTo("Acoffee");
acoffeeQuery.addValueEventListener(new ValueEventListener() {
    Override
    public void onDataChange(DataSnapshot snapshot) {
        final int size = (int) snapshot.getChildrenCount();
        //size is equal to 2
    }

    @Override
    public void onCancelled(FirebaseError firebaseError) {}
});


This way you don't have to iterate over all the results, and you don't have to manually iterate over the counter.

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Please use the following code:

Firebase rootRef = new Firebase("https://....../myCoffee/" + phone);
rootRef.addValueEventListener(new ValueEventListener() {
    Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        int size = 0;
        for (DataSnapshot ds : dataSnapshot.getChildren()) {
            String coffeeNo = ds.child("coffeeNo").getValue(String.class);
            if(coffeeNo.equals("Acoffee")) {
                size++;
            }
        }
        txtMyCoffee.setText(String.valueOf(size));
    }

    @Override
    public void onCancelled(FirebaseError firebaseError) {}
});

Edit: Another approach is to use a simple query

one like this:



Firebase rootRef = new Firebase("https://....../myCoffee/"+phone+"");
Query query = rootRef.orderByChild("coffeeNo").equalTo("Acoffee");
query.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        int size = (int) dataSnapshot.getChildrenCount();
        txtMyCoffee.setText(String.valueOf(size));
    }

    @Override
    public void onCancelled(FirebaseError firebaseError) {}
});

In your case it txtMyCoffee

will be displayed: 2

.

+2


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Firebase myFirebaseRef = new Firebase("https://....../myCoffee/"+phone+"");
        myFirebaseRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                int count=0;
                for(DataSnapshot item: dataSnapshot.getChildren())
                {
                         String coffeeNo=item.child("coffeeNo").toString();
                         if(coffeeNo.equals("Acofee")
                              count+=1;
                }
            @Override
            public void onCancelled(FirebaseError firebaseError) {
            }
        });

Try something like this

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