如何使用Firebase实时数据库创建一个特定用户保存的所有帖子的列表？

Question

FirebaseDatabase.getInstance().getReference()
            .child("Posts")
            .child("saves")
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot snapshot) {
                    mySavedPosts.clear();
                    if (snapshot.child(FirebaseAuth.getInstance().getCurrentUser().getUid()).exists()){
                        for (DataSnapshot dataSnapshot : snapshot.getChildren()){
                            Post post = dataSnapshot.getValue(Post.class);
                            mySavedPosts.add(post);
                        }
                    }
                    Collections.reverse(mySavedPosts);
                    postAdapterSaves.notifyDataSetChanged();
                }

                @Override
                public void onCancelled(@NonNull DatabaseError error) {

                }
            });

Answer 1

根据你的评论：

我只需要看看auth.getuid（）是否在“saves”的子项中。

要检查经过身份验证的用户的UID是否存在于“保存”节点中，请使用以下代码行：

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference postsRef = rootRef.child("Posts");
Query query = postsRef.orderByChild("saves/" + uid).equalTo(true);
query.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if (task.isSuccessful()) {
            for (DataSnapshot postSnapshot : task.getResult().getChildren()) {
                Post post = postSnapshot.getValue(Post.class);
                mySavedPosts.add(post);
            }
            Collections.reverse(mySavedPosts);
            postAdapterSaves.notifyDataSetChanged();
        } else {
            Log.d("TAG", task.getException().getMessage()); //Don't ignore potential errors!
        }
    }
});