如何从firebase

Question

我使用过firebaase recyclerview，并使用json上传填充它。 我有在JSON文件中订购的项目，并希望以相同的顺序接收它们。但是，每次我在我的应用程序中混淆它。怎么解决这个问题？

public class NoticesFragment extends Fragment {

    private RecyclerView mNoticesList;
    private DatabaseReference mDatabase;
//    private ProgressDialog vProgress;
    private View rootview;
    private FirebaseRecyclerAdapter<Notices,NoticeViewHolder> firebaseRecyclerAdapter;


    public NoticesFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
         rootview = inflater.inflate(R.layout.fragment_notices, container, false);
        Toast.makeText(getActivity(),"Please Wait While Load , It May Take Some Time ...", Toast.LENGTH_SHORT).show();

        mDatabase = FirebaseDatabase.getInstance().getReference().child("notice");

        mNoticesList = (RecyclerView) rootview.findViewById(R.id.notices_list);

        mNoticesList.setLayoutManager(new LinearLayoutManager(  getActivity() ) );

        mNoticesList.setHasFixedSize(true);

        return rootview;
    }


    @Override
    public void onStart() {
        super.onStart();

         firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Notices, NoticeViewHolder>(

                Notices.class,
                R.layout.list_view_row,
                NoticeViewHolder.class,
                mDatabase

        ) {
            @Override
            protected void populateViewHolder(NoticeViewHolder viewHolder, Notices model, int position) {
                    viewHolder.setRefertext(model.getRefer());
                    viewHolder.setDatetext(model.getDate());
                    viewHolder.setLink(model.getLink());
            }
        };



        mNoticesList.setAdapter(firebaseRecyclerAdapter);

    }

    public static class NoticeViewHolder extends RecyclerView.ViewHolder{

        final View mView;
        private String link;
        private Intent myIntent;
         public NoticeViewHolder(View itemView) {
            super(itemView);

             mView = itemView;
             mView.setOnClickListener(new View.OnClickListener() {
                 @Override
                 public void onClick(View v) {
                     try {
                         Intent myIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(link));
                         mView.getContext().startActivity(myIntent);
                     } catch (ActivityNotFoundException e) {
                         Toast.makeText(mView.getContext(),"No Activity found to handle the request ",Toast.LENGTH_LONG).show();
                         e.printStackTrace();
                     }
                 }
             });

        }
        public void setRefertext(String refertext){
            TextView referText = (TextView) mView.findViewById(R.id.refer_text);
            referText.setText(refertext);
        }

        public void setDatetext (String datetext){
            TextView dateText = (TextView) mView.findViewById(R.id.date_text);
            dateText.setText(datetext);

        }

        public void setLink (String link){
            this.link = link;

        }

    }







}

我该怎么做才能将我上传到firebase的有序JSON？我想以相同的顺序取回物品。

Answer 1

根据定义，JSON是无序的。因此，您上传的JSON文件中的项目存在的方式会丢失，因为它会持久保存到数据库中。

要订购数据，您在检索数据时使用Firebase的orderBy...方法。例如，如果您的通知具有时间戳属性，则可以使用以下命令在Recycler视图中对其进行排序：

firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Notices, NoticeViewHolder>(

    Notices.class,
    R.layout.list_view_row,
    NoticeViewHolder.class,
    mDatabase.orderByChild("timestamp")

) {

我建议您花一些时间在Firebase documentation，特别是section on ordering and filtering。