DataSnapshot.getValue(valueType) with key

[Andrey]

Hello!

My question relates to this example from the docs:

// Get a reference to our posts
  Firebase ref = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts");


  // Attach an listener to read the data at our posts reference


  ref.addValueEventListener(new ValueEventListener() {
      @Override
      public void onDataChange(DataSnapshot snapshot) {
          System.out.println("There are " + snapshot.getChildrenCount() + " blog posts");
          for (DataSnapshot postSnapshot: snapshot.getChildren()) {
            BlogPost post = postSnapshot.getValue(BlogPost.class);
            System.out.println(post.getAuthor() + " - " + post.getTitle());
          }
      }


      @Override
      public void onCancelled(FirebaseError firebaseError) {
          System.out.println("The read failed: " + firebaseError.getMessage());
      }
  });

I would like to know, is there a possibility to retrieve not only values by DataSnapshot.getValue(valueType) method, but also a key name?

I need it to to go from list to details view, for example, or perform data modification in specific item(blog post in example).

Thanks!

[Jacob Wenger]

Yes, I think you are looking for DataSnapshot.getKey().

Cheers,

Jacob

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[Andrey]

Hello, Jacob!

Thanks for you reply! I know about DataSnapshot.getKey().

What I meant is that in the example BlogPost class looks like this :

public class BlogPost {
  private String author;
  private String title;

  public BlogPost() {
    // empty default constructor, necessary for Firebase to be able to deserialize blog posts
  }

  public String getAuthor() {
    return author;
  }

  public String getTitle() {
    return title;
  }
}

And I my version have an extra field - "key":

public class BlogPost {
  private String key;
  private String author;
  private String title;

  public BlogPost() {
    // empty default constructor, necessary for Firebase to be able to deserialize blog posts
  }

  public String getKey() {
    return key;
  }

  public String getAuthor() {
    return author;
  }

  public String getTitle() {
    return title;
  }
}

And i want to know is there a version of DataSnapshot.getValue() that can fill all fields including "key" as easy as in example:

BlogPost post = postSnapshot.getValue(BlogPost.class);

I understand that I can store key name in real "key" field and it will store it in child node like this:

{
    blogPosts: [
            "-KD2YN5tJNqsxcDhpXRP": {
                 key: "-KD2YN5tJNqsxcDhpXRP",
                 author: "Andrey",
                 title: "Hello!"
            }
    ]
}

but I just wander, if it can be achieved without data duplication?

Thanks!

[Frank van Puffelen]

You could inject it with some well-placed Jackson annotiations.

But you should really wonder if this is the right approach to take. In general on Android I prefer to separate the value of an object with a reference to that object in the database. The value you get with snapshot.getValue(), the reference you get with snapshot.getRef().  If I want something that you can both get the value and the location from, I pass around the snapshot itself.

[Andrey]

Thank you, Frank!

You are right, it is a better approach to pass  snapshot itself.

I was thinking about that all the weekends, and end up with an idea, that it would be awesome to have Java analogue of AngularFire synchronized object/array, so one can use it like this:

FirebaseObject<BlogPost>   post = new FirebaseObject<BlogPost>(firebaseRef);


post.addValueEventListener(new ValueEventListener<BlogPost>() {
    @Override
    public void onDataChange(BlogPost value) {
        System.out.println(value.title);

    }
    @Override
    public void onCancelled(FirebaseError firebaseError) {
        System.out.println("The read failed: " + firebaseError.getMessage());
    }
});

post.title = "new title";
post.save();

[Frank van Puffelen]

There is an equivalent to $firebaseArray in FirebaseUI called FirebaseListAdapter (or FirebaseRecyclerAdapter). Both build on a class called FirebaseArray, which handles the synchronization of database changes into the Android app.

There is currently no equivalent for $firebaseObject in FirebaseUI. We are intentionally skipping on three-way data binding for the moment.