java Datasnapshot映射到对象后，对象显示空值

Question

我想从firebase数据库获取数据，我使用了valueEventListner Datasnapshot包含数据，但当它映射到用户对象时，对象将所有属性显示为null。请提出解决方案

    mDatabaseReference =mFireBaseDatabase.getReference(table_name);
    mDatabaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            Log.v(TAG,"user snap shot count:"+dataSnapshot.getChildrenCount());
            // users is arraylist
        users.clear();
                for(DataSnapshot usersnapshot : dataSnapshot.getChildren())
                {
                    Log.v(TAG,"Profile user snap:"+usersnapshot.toString());

                   User user = usersnapshot.getValue(User.class);

                    Log.v(TAG,"user data:"+user.toString());
                }

        }

Answer 1

当您插入数据时，时间会通过用户对象，如下所示

        User user = new User(name, email, pwd);
    mFirebaseDatabase.child(name).setValue(user);

然后你的代码就好了，我想当你读数据的时候，你就可以定义firebase实例了

        mFirebaseInstance = FirebaseDatabase.getInstance();
  mDatabase = mFirebaseInstance.getReference("usersDb/UserTable");