Question

我有以下数据结构

  "messages" : {
    "Johnny_peter" : {
       "-KsjbzGUO90vejwHpzqx" : {
          "message" : "how are u doing",
          "user" : "peter",
          "userName" : "peter"
  }
},
   "guy_steve" : {
     "-Ksj5vkO5H4qeleFqojh" : {
         "message" : "merci",
         "user" : "steve",
         "userName" : "steve"
  }

我正在使用关注代码来检索用户名

的值

  mDatabase = FirebaseDatabase.getInstance().getReference(Constants.DATABASE_PATH_CHATLISTS);

    //adding an event listener to fetch values
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            //dismissing the progress dialog
            progressDialog.dismiss();


            //iterating through all the values in database
            for (DataSnapshot postSnapshot : snapshot.getChildren()) {

                ChatList chatlist= postSnapshot.getValue(ChatList.class);

                    chatLists.add(chatlist);
            }
            //creating adapter
            adapter = new MyAdapterChatList(getApplicationContext(), chatLists);

            //adding adapter to recyclerview
            recyclerView.setAdapter(adapter);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            progressDialog.dismiss();
        }
    });

问题：使用上面的代码，我无法检索userName的值任何帮助都值得赞赏

Answer 1

要实现此目的，请使用以下代码：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference messagesRef = rootRef.child("messages");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            for(DataSnapshot dSnapshot : ds.getChildren()) {
                String userName = dSnapshot.child("userName").getValue(String.class);
                Log.d("TAG", userName);
            }
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
messagesRef.addListenerForSingleValueEvent(eventListener);

您的输出将是：

peter
steve

Android：从firebase检索值

1 个答案: