Get Value from Firebase Database

Josh Published at Dev

Josh

I need to get the string value from the node passcode in my Firebase database to compare with a user input, but unfortunately I am not able to get the value. This is the link to my firebase database in the below image.

Firebase Database screenshot

This is my codes below:

 final DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference("pin_code");

        mDatabase.addListenerForSingleValueEvent(new com.google.firebase.database.ValueEventListener() {
            @Override
            public void onDataChange(com.google.firebase.database.DataSnapshot dataSnapshot) {
                String rface = (String) dataSnapshot.child("pincode").getValue();
                if (rface.equals(userPassword) && !rface.equals("")){
                    Intent intent = new Intent(PinActivity.this, ProfileActivity.class);
                    startActivity(intent);
                }
                else {
                    if (rface.equals("") || rface.equals(null)){
                        // Creating new user node, which returns the unique key value
                        // new user node would be /users/$userid/
                        String userId = mDatabase.push().getKey();

                        // creating user object
                        Pin pin = new Pin(authUserId, userPassword);

                        mDatabase.child(userId).setValue(pin);

                        Intent intent = new Intent(PinActivity.this, ProfileActivity.class);
                        startActivity(intent);
                    }
                    else {
                        Toast.makeText(PinActivity.this,"Invalid PIN code", Toast.LENGTH_SHORT).show();
                        return;
                    }

                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });

This is the json code

  {
  "pin_code" : {
"id" : "TQYTo1NHNnhPJnOxhe1Vok3U6ic2",
"pincode" : "12345"
     }
  }

Frank van Puffelen

This FirebaseDatabase.getInstance().getReference("pin_code") does not refer to the node you're looking for. Most likely you know the id property, in which case you can get the node with:

DatabaseReference collection = FirebaseDatabase.getInstance().getReference("p...");
Query query = collection.orderByChild("id").equalTo("TQT...ic2");

query.addListenerForSingleValueEvent(new com.google.firebase.database.ValueEventListener() {
    @Override
    public void onDataChange(com.google.firebase.database.DataSnapshot dataSnapshot) {
      for (DataSnapshot child: dataSnapshot.getChildren()) {
        String rface = (String) child.child("pincode").getValue();
        if (rface.equals(userPassword) && !rface.equals("")){

The changes I made:

On the first line we get the collection: the node under which you want to run a query. You struck out the name of that node in the screenshot, but it's the second line you marked.
In the second line we create a query on the id property of each child node under the collection.
In the onDataChange we added a loop. This is needed because a query against the Firebase Database will potentially have multiple results. So the dataSnapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result. We loop over dataSnapshot.getChildren() to handle those multiple results.

If there can ever only be one node with the same id, you should consider changing your data structure to use the id as the key of the node. So:

pin_codes
  uid1: "pincode1"
  uid2: "pincode2"

Your code then becomes significantly simpler, because you don't need to query for the user anymore. You can just directly read from the path:

DatabaseReference user = FirebaseDatabase.getInstance().getReference("pin_codes").child("TQT...ic2");

user.addListenerForSingleValueEvent(new com.google.firebase.database.ValueEventListener() {
    @Override
    public void onDataChange(com.google.firebase.database.DataSnapshot dataSnapshot) {
        String rface = (String) dataSnapshot.getValue();
        if (rface.equals(userPassword) && !rface.equals("")){

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Please contact [email protected] to delete if infringement.

edited at2021-04-20

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