用户列表为空 [英] Users list empty

问题描述

我正在尝试从RealTime-Database中检索其名字和名字的用户列表，但是什么也没有出现.

I'm trying to retrieve from RealTime-Database the list of users with their First name and second name but nothing appears.

UsersActivity类显示数据库中的所有用户.我尝试了很多教程，但似乎无济于事.

The class UsersActivity show all the users from the database.I tried a lot of tutorials but nothing seems to work.

public class UsersActivity extends AppCompatActivity {
    private RecyclerView userslist;
    private DatabaseReference ref;
    private List<Users> mUsers;

    @Override
    protected void onCreate (Bundle savedInstanceState) {
        super.onCreate ( savedInstanceState );
        setContentView ( R.layout.activity_users );
        ref = FirebaseDatabase.getInstance ().getReference ().child ( "FirstName" );

        userslist = (RecyclerView) findViewById ( R.id.users_list );

        userslist.setHasFixedSize ( true );
        userslist.setLayoutManager ( new LinearLayoutManager ( this ) );


    }
    public void readUsers(){
        FirebaseUser firebaseUser= FirebaseAuth.getInstance ().getCurrentUser ();
        DatabaseReference reference=FirebaseDatabase.getInstance ().getReference ("spors-budy-en866");
        reference.addValueEventListener ( new ValueEventListener () {
            @Override
            public void onDataChange (@NonNull DataSnapshot dataSnapshot) {

            }

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

            }
        } )
    }

    @Override
    protected void onStart () {
        super.onStart ();
        FirebaseRecyclerOptions<Users> options = new FirebaseRecyclerOptions.Builder<Users> ()
                .setQuery ( ref, Users.class )
                .build ();
        FirebaseRecyclerAdapter<Users, FindFriendViewHolder> adapter = new FirebaseRecyclerAdapter<Users, FindFriendViewHolder> ( options ) {
            @Override
            protected void onBindViewHolder (@NonNull FindFriendViewHolder findFriendViewHolder, int i, @NonNull Users users) {
                findFriendViewHolder.userName.setText ( users.getName () );

            }

            @NonNull
            @Override
            public FindFriendViewHolder onCreateViewHolder (@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from ( parent.getContext () ).inflate ( R.layout.users_template, parent, false );
                FindFriendViewHolder viewHolder = new FindFriendViewHolder ( view );
                return viewHolder;
            }
        };
        userslist.setAdapter ( adapter );
        adapter.startListening ();
    }

    public static class FindFriendViewHolder extends RecyclerView.ViewHolder {
        TextView userName;
        ImageView profileImage;

        public FindFriendViewHolder (@NonNull View itemView) {
            super ( itemView );
            userName = itemView.findViewById ( R.id.username1 );
            profileImage = itemView.findViewById ( R.id.profilepicture );

        }


    }
}

我的数据库规则:

{
  "rules": {
    ".read": "true",
      ".write":"true",
    "users":{
    "$user_id":{
       ".read": "auth.uid === $user_id",
       ".write": "auth.uid === $user_id"

    }
  }
}
}

我希望显示数据库中的所有用户.但是活动为空.

I expect to show all the users from my databse.But the activity is empty.

推荐答案

您正在设置:

ref = FirebaseDatabase.getInstance().getReference().child("FirstName");

然后使用它来初始化FirebaseUI适配器:

And then use that to initialize the FirebaseUI adapter:

FirebaseRecyclerOptions<Users> options = new FirebaseRecyclerOptions.Builder<Users> ()
        .setQuery(ref, Users.class )

虽然我不知道您的数据模型，但似乎不太可能在/FirstName下有一个用户列表，这是使用FirebaseUI适配器显示这些用户所必需的.

While I don't know your data model, it seems unlikely that you'd have a list of users under /FirstName, which is what is required to show those users with the FirebaseUI adapter.

更可能将ref初始化为:

More likely ref should be initialized as:

ref = FirebaseDatabase.getInstance().getReference("users")

这篇关于用户列表为空的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！