CODEWITHSUNDEEP
androidfirebase-realtime-databasetimestamp
Amal
Amal

Reputation: 299

Saving TimeStamp as a negative value using ServerValue.TIMESTAMP in FireBase Database

I want to save the data in firebase database with a descending order and I found that the solution is to add a timeStamp field with a negative value, but using ServerValue.TIMESTAMP save only the value in a positive way,so how can I save a negative timeStamp in my FireBase :

Code of model:

public class Book{
    Object createdTimestamp;
    String nom_livre;
    String desc_livre;
    String prix_livre;
    String id_book;
    String id_user;

    public Book() {
        super();
    }

    public Book(String nom_livre, String desc_livre, String prix_livre, String id_book,String id_user,  Object createdTimestamp) {
        super();

        this.nom_livre = nom_livre;
        this.desc_livre = desc_livre;
        this.prix_livre = prix_livre;
        this.id_book = id_book;
        this.id_user=id_user;
        this.createdTimestamp=  createdTimestamp;

    }
    @Exclude
    public long getCreatedTimestampLong(){
        return (long)createdTimestamp;
    }

   //other getters and setters
}

Code of adding data in fireBase , im my case I'm creating a Book on addBookActivity:

private void createBook(String nom_livre, String desc_livre,String prix_livre,Object createdTimestamp) {

        bookInfos=new Book(nom_livre,desc_livre,prix_livre,idLivre,id, ServerValue.TIMESTAMP );

            myRefBook.child(idBook).setValue(bookInfos);

    }

enter image description here

Upvotes: 0

Views: 242

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317457

You have two options, and they both require a second write to the database after you initially write the regular timestamp number as a positive number.

If you only want to write data on the client app, what you can do is write your createdTimestamp as you are right now, then read that value back into the client by listening to the location that you just wrote. After you read it back in, you'll have the actual timestamp value. Then, you can easily compute the negative it and write it back where you want it (maybe revCreatedTimestamp, if you're using it to sort in reverse chronological order).

Your other option is to use Cloud Functions for Firebase to write a Realtime Database trigger to respond to writes that match the location /books/{book_id} where book_id is that string you're generating for the book. That trigger can then capture the timestamp and write back the negative version at the same location.

Upvotes: 1

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