如何将用户id从适配器传递到活动

Question

        reference = FirebaseDatabase.getInstance().getReference("parent");

        intent = getIntent();
        final String currentSubject = intent.getStringExtra("currentSubject");
        reference.addValueEventListener(new ValueEventListener() {
            @RequiresApi(api = Build.VERSION_CODES.O)
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {

                    final User user = snapshot.getValue(User.class);

                    ZoneId zonedId = ZoneId.of("America/Montreal");
                    final LocalDate today = LocalDate.now(zonedId);

                        reference = FirebaseDatabase.getInstance().getReference("attendance").child(user.getSchoolcode()).child(grade.getText().toString() + " " + section.getText().toString()).child(currentSubject).child(today.toString()).child(userID);

                        reference.addValueEventListener(new ValueEventListener() {
                            @Override
                            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                                HashMap<String, Object> hashMap = new HashMap<>();
                                hashMap.put("attendance", "yes");
                                reference.updateChildren(hashMap);
                            }

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

                            }
                        });
                    }
            }

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

我想把它从适配器传递到这个，这是我的适配器

public class StudentAdapter extends RecyclerView.Adapter<StudentAdapter.ViewHolder> {

    private Context context;
    private List<User> users;


    public StudentAdapter(Context context, List<User> users) {
        this.context = context;
        this.users = users;
    }
    DatabaseReference reference;

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.student_item, parent, false);
        return new StudentAdapter.ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {
        final User user = users.get(position);

        holder.studentName.setText(user.getStudentname() + " " + user.getLastname());

    }

    @Override
    public int getItemCount() {
        return users.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        public TextView studentName;
        public Switch aSwitch;

        public ViewHolder(View itemView) {
            super(itemView);

            studentName = itemView.findViewById(R.id.studentName);
            aSwitch = itemView.findViewById(R.id.attendanceSwitch);
        }
    }

这是我的适配器，它保存着RecycerView，我正在尝试获取考勤活动上查看的用户id RecycerView

Answer 1

您可以使用的一种方法是回调:

在适配器中定义如下接口：

public class StudentAdapter extends RecyclerView.Adapter<StudentAdapter.ViewHolder> {

 private SendCallBack mCallback;

    interface SendCallBack {
        void send(int id);
    }

//Initial callback in constructor
   public StudentAdapter(Context context, List<User> users,SendCallBack callback) {
        this.context = context;
        this.users = users;
        mCallback = callback;
    }

//Now in where that you want to pass data use this

    mCallback.send(user.getID);

}

现在，在活动中实现回调，如下所示：

public class YourActivty implements  YourAdapter.SendCallback {

    @Override
    public void send(int id) {


    }

//For pass callBack for your adapter constructor use this

}