无法从 firebase 数据库 android 中检索数据，回收站视图

Question

Model Class 代码

public class DeleteEditEventsModel
{
    private String title, description, date, time, venue;

    DeleteEditEventsModel() { }

    public DeleteEditEventsModel(String title, String description, String date, String time, String venue) {
        this.title = title;
        this.description = description;
        this.date = date;
        this.time = time;
        this.venue = venue;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public String getVenue() {
        return venue;
    }

    public void setVenue(String venue) {
        this.venue = venue;
    }
}

这个 class 有什么问题吗？

适配器 Class 代码：

public class DeleteEditEventsAdapter extends FirebaseRecyclerAdapter<DeleteEditEventsModel, DeleteEditEventsAdapter.myViewHolder> {

    public DeleteEditEventsAdapter(@NonNull FirebaseRecyclerOptions<DeleteEditEventsModel> options) {
        super(options);
    }

    @Override
    protected void onBindViewHolder(@NonNull final myViewHolder holder, final int position, @NonNull final DeleteEditEventsModel model) {

        holder.title.setText(model.getTitle());
        holder.description.setText(model.getDescription());
        holder.date.setText(model.getDate());
        holder.time.setText(model.getTime());
        holder.venue.setText(model.getVenue());


        holder.delete_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                FirebaseDatabase.getInstance().getReference().child("Events")
                        .child(getRef(position).getKey()).removeValue();
            }
        });
    }

    @NonNull
    @Override
    public myViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_delete_events, parent, false);
        return new myViewHolder(view);
    }

    class myViewHolder extends RecyclerView.ViewHolder {

        TextView title, description, date, time, venue, edit_btn, delete_btn;


        public myViewHolder(@NonNull View itemView) {
            super(itemView);

            title = (TextView) itemView.findViewById(R.id.delete_event_Title);
            description = (TextView) itemView.findViewById(R.id.delete_event_Description);
            date = (TextView) itemView.findViewById(R.id.delete_event_Date);
            time = (TextView) itemView.findViewById(R.id.delete_event_Time);
            venue = (TextView) itemView.findViewById(R.id.delete_event_Venue);
            edit_btn = (TextView) itemView.findViewById(R.id.delete_event_edit_btn_tv);
            delete_btn = (TextView) itemView.findViewById(R.id.delete_event_btn_TV);
        }
    }

}

活动 class

public class DeleteEditEventsActivity extends AppCompatActivity {

    RecyclerView recyclerView;
    DeleteEditEventsAdapter adapter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_delete_events);

        recyclerView = (RecyclerView) findViewById(R.id.delete_events_recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setHasFixedSize(true);



        FirebaseRecyclerOptions<DeleteEditEventsModel> options =
                new FirebaseRecyclerOptions.Builder<DeleteEditEventsModel>()
                .setQuery(FirebaseDatabase.getInstance().getReference("Events"), DeleteEditEventsModel.class)
                .build();

        adapter = new DeleteEditEventsAdapter(options);

        recyclerView.setAdapter(adapter);
    }

    @Override
    protected void onStart() {
        super.onStart();
        adapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        adapter.stopListening();
    }
}

JSON 文件

{
  "CSE Notification" : {
    "cse notification" : "Computer Science and Engineering"
  },
  "Central Notification" : {
    "central notification" : "Inn-sha-ALLAH we'll be doing"
  },
  "Civil Notification" : {
    "civil notification" : "civil"
  },
  "ECE Notification" : {
    "ece notification" : "ece"
  },
  "EEE Notification" : {
    "eee notification" : "eee"
  },
  "Events" : {
    "21:00" : {
      "EventDate" : "08/05/21",
      "EventDescription" : "laptops",
      "EventTime" : "21:00",
      "EventTitle" : "Lenovo",
      "EventVenue" : "Hyderabad"
    },
    "5:16" : {
      "EventDate" : "17/05/21",
      "EventDescription" : "To retrieve",
      "EventTime" : "5:16",
      "EventTitle" : "Trying",
      "EventVenue" : "Hyderabad"
    }
  },
  "Examination_Branch_Notification" : {
    "em_noti" : "AstagfiruILLAH"
  },
  "IT Notification" : {
    "it notification" : "Information Technology"
  },
  "MBA Notification" : {
    "mba notification" : "mba"
  },
  "MECH Notification" : {
    "mech notification" : "MECH"
  },
  "M_TECH_Notification" : {
    "mTech" : "Master of Technology"
  }
}

我认为我的 model class 有问题

如您所见，数据未送入卡中

我第二次使用回收器视图，但我已经检查了我的代码与以前的代码完全相同（正如我已经验证的那样），但这里无法理解问题。

Answer 1

当您尝试将实时数据库中的节点 map 插入“DeleteEditEventsModel”类型的 object 时，class 中存在的字段名称必须与数据库中存在的属性名称匹配不幸的是，在您的情况下，这些字段不匹配。 看，数据库中的字段以“事件”开头，而在 class 中不是，这是不正确的。

为了解决这个问题，您有两个选择，您可以更改数据库中的属性名称以匹配 class 中的名称，或者您可以在 getter 前面使用注释。 例如，如果您有一个名为“date”的字段并且数据库中的属性名为“EventDate”，那么您的 getter 应该如下所示：

@PropertyName("EventDate")
public String getDate() {
    return date;
}

通过这种方式，您告诉编译器查找名为“EventDate”而不是“日期”的属性。