Read Data From Firebase database

Question

I want to read specific data from firebase database. What I am currently doing is here.

DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference myRef = database.child("profiles/");

myRef.child(phoneNo).addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        user = dataSnapshot.getValue(User.class);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}

});

Method to write to DB

public void writeToDBProfiles(Object data,String phoneNo) {
    DatabaseReference database = FirebaseDatabase.getInstance().getReference();
    DatabaseReference myRef = database.child("profiles/" + phoneNo);
    myRef.setValue(data);
}

But its returning null... Any help will be appreciated.

Answer 1

If you want to get a specific data using a phone number then you can use a Query like this

DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = database.child("profiles");

Query phoneQuery = ref.orderByChild(phoneNo).equalTo("+923336091371");
phoneQuery.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot singleSnapshot : dataSnapshot.getChildren()){
           user = singleSnapshot.getValue(User.class); 
        }
    }
    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.e(TAG, "onCancelled", databaseError.toException());
    }
});

I think this is the best method.

Answer 2

Ok, I got it sorted out. the above code in the question is perfectly fine and should work . I am explaining for later users who might have the same issue due to mistakes which I made.

the singleSnapshot.getValue(User.class); was unable to cast the result to user class because when uploading the data i.e. in setValue I had my photoUrl equal to null and as a result you can see the photoUrl is not present in my child node. So what I believe is (and maybe someone want correct me on this) that my singleSnapshot.getValue method was unable to cast the result.

So for now I have omitted photoUrl from my User class and will get back to it when I will start working withe relevant module.

Thanks again everyone for all the suggestions and help.

public class User {
String name;
Uri photoURL;
String bloodGroup;
String city;
String country;
double latitude;
double longitude;
boolean availableToDonate;

// Get, set and constructors are obvious here I am just saving some space in the post
}