java - 当 onChildAdded 事件被触发时，如何在 Firebase 中获取父项？

Question

考虑以下代码示例:

// Get a reference to our posts
Firebase ref = new Firebase("https://docs-examples.firebaseio.com/web/saving-data/fireblog/posts");
ref.addChildEventListener(new ChildEventListener() {
// Retrieve new posts as they are added to the database
@Override
public void onChildAdded(DataSnapshot snapshot, String previousChildKey) {
    BlogPost newPost = snapshot.getValue(BlogPost.class);
    System.out.println("Author: " + newPost.getAuthor());
    System.out.println("Title: " + newPost.getTitle());
}
//... ChildEventListener also defines onChildChanged, onChildRemoved,
//    onChildMoved and onCanceled, covered in later sections.
});

触发 onChildAdded 时是否可以在 Firebase 中获取 DataSnapshot 父项？

Answer 1

由于您只检索了子项，因此 DataSnapshot 不包含父项的数据。但可以通过 ref 轻松访问它。

public void onChildAdded(DataSnapshot snapshot, String previousChildKey) {
  ref.addListenerForSingleValueEvent(new ValueEventListener() {
    public void onDataChange(DataSnapshot parent) {
      System.out.println("Got parent");
    }
    ...
  });
}