CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-database
AV114
AV114

Reputation: 41

Get specific child data from firebase

I have to access a child from a node. I have only "value" for a specific child and to get the Type value from the same node.

I have to return the value:

Structure

I've done a lot of googling and I just can't figure out how this works. My current version of the java code is this.

private String GetCategory(String sName ) {
    DatabaseReference db = FirebaseDatabase.getInstance().getReference("Category");
    Query query = db.orderByValue().equalTo("Salary");//.orderByValue().equalTo("Salary");


    query.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
                String eType = userSnapshot.child("Type").getValue(String.class);
                Log.d("Catagory","Value"+ eType);
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });
}

Upvotes: 1

Views: 658

Answers (2)

Alex Mamo
Alex Mamo

Reputation: 138824

Creating a reference to the Category node, attaching a listener to getting all children of the node and do a comparison on the client, is not the best option to go ahead with. If your node will contain 1 MIL children, are you willing to download all of them in order to read only a single one? That's an incredible waste of bandwidth and resources. What you should do, is to create a Query that can return only the information you are interested in. Assuming you need the information from the first child, please use the following lines of code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference categoryRef = rootRef.child("Category");
Query queryByName = categoryRef.orderByChild("Name").equalTo("Salary");
queryByName.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if (task.isSuccessful()) {
            for (DataSnapshot snapshot : task.getResult().getChildren()) {
                String type = snapshot.child("Type").getValue(String.class);
                Log.d("TAG", type);
            }
        } else {
            Log.d("TAG", task.getException().getMessage()); //Don't ignore potential errors!
        }
    }
});

The result in the logcat will be:

 Income

Assuming that the first object is the only one that satisfies the Query, then you'll get only a single element from the database. This is extremely fast and consumes an incredibly small amount of data.

Upvotes: 0

Jabal Logian
Jabal Logian

Reputation: 2342

Get a specific node inside Category

If you want to get the node which id is 1, you could try this:

private String GetCategory(String sName ) {
    DatabaseReference db = FirebaseDatabase.getInstance().getReference("Category");

    db.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
                // check for desired id here
                if(userSnapshot.getKey().equals("1")) {
                    String icon = userSnapshot.child("Icon").getValue().toString();
                    String name = userSnapshot.child("Name").getValue().toString();
                    String type = userSnapshot.child("Type").getValue().toString();
                }
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });
}

Output of the code above:

icon = "01"
name = "Salary"
type = "Icome"

Get all nodes inside Category

If you want to read all the node inside Category, just provide an array of hash map or class and change the onDataChange method like this:

ArrayList<ExampleClass> array = new ArrayList<>();
for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
    ExampleClass example = new ExampleClass();
    example.setIcon(userSnapshot.child("Icon").getValue().toString());
    example.setName(userSnapshot.child("Name").getValue().toString());
    example.setType(userSnapshot.child("Type").getValue().toString());
}

but first, you have to create the ExampleClass file with setter and getter functions inside it.

Output:

array[0].getIcon = "01"
array[0].getName = "Salary"
array[0].getType = "Icome"

...

array[2].getIcon = "07"
array[2].getName = "Other Income"
array[2].getType = "Income"

Upvotes: 2

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