Java/Android - Error loading ArrayList as Object from Firebase

Question

Been trying to solve this Firebase loading arraylist problem for a while now but no idea how to get it solved.

Object Class

public class Book {
    private String title;
    private String author;
    private String ISBN;
    private String photo;
    private String ownerEmail;
    private String ownerID;
    private String BookID;
    private Date returnDate;
    private Status status;
    private String borrowerID;

    public Book(){}
    public Book(String title, String author, String ISBN, String photo, String ownerEmail, String ownerID) {
        this.title = title;
        this.author = author;
        this.ISBN = ISBN;
        this.photo = photo;
        this.ownerEmail = ownerEmail;
        this.ownerID = ownerID;
        this.status = Status.Available;
        if(this.BookID == null || this.BookID.isEmpty())
            this.BookID = UUID.randomUUID().toString();
    }
    public enum Status{
        Available,
        Requested,
        Accepted,
        Borrowed
    }

I have getter and setter for all the variables, and what I'm doing is load this information from firebase using the code:

 public void loadMyBookFromFirebase(){
        final ArrayList<Book> bookList = new ArrayList<>();

        DatabaseReference userReference = FirebaseDatabase.getInstance().getReference().child("users").child(this.userID).child("myBooks");
        userReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                Log.d("testing","books" + dataSnapshot.toString());
                if(dataSnapshot.exists()) {
                    try {
                        for (DataSnapshot books : dataSnapshot.getChildren()) {
                            Book book = dataSnapshot.getValue(Book.class);
                            Log.d("testing","books" + book.getAuthor());
                            //load book into ListView
                        }
                    } catch (Exception e){
                        e.printStackTrace();
                    }
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Log.w("testing","Error: ", databaseError.toException());
            }
        });
    }

this is my firebase database firebase database i keep getting a Can't convert object of type java.util.ArrayList to type com.example.cmput301w19t15.Book

error on the line Book book = dataSnapshot.getValue(Book.class); im not sure why i am getting the convert object error, i do not want to search for individual variables and set them, which defeat the purpose of the object class

I would really like some insight on this

Please upload the database structure

Bhaskar Jyoti Dutta
– Bhaskar Jyoti Dutta

2019-03-04 16:54:55 +00:00
Commented Mar 4, 2019 at 16:54 — Bhaskar Jyoti Dutta
– Bhaskar Jyoti Dutta, Commented Mar 4, 2019 at 16:54

Alex Mamo · Accepted Answer · 2019-03-04 16:58:12Z

1

To solve this, please change the following line of code:

Book book = dataSnapshot.getValue(Book.class);

to

Book book = books.getValue(Book.class);

You need to get the data from the books object and not from the dataSnapshot object.

answered Mar 4, 2019 at 16:58

Alex Mamo

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1 Comment

Anjesh Shrestha Over a year ago

thanks a lot, that was an oversight, did not notice at all

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