我无法从我的firebasedatabase获得价值

Question

运行程序时我会遇到此错误： com.cdirect.agenda2.allevents $ 1.DATATACHANGE（Pleatents.java:47） - events events = datasnapshot.getValue（event.class）;

我想从我的firebasedatabase获取所有数据。我创建了Event.java。它有Getter和Setter。 MyAdapter正在适应Partents.java上的回收。我想显示Parevents.java上的所有数据。 但是我无法成功。你能帮助我吗？

myadapter.java：myevents.java

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
Context context;
ArrayList<Events> list;
public MyAdapter(Context context, ArrayList<Events> list) {
    this.context = context;
    this.list = list;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(context).inflate(R.layout.evententry,parent,false);
    return new MyViewHolder(v);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
    Events events = list.get(position);
    holder.plan.setText(events.getPlan());
    holder.note.setText(events.getNote());
    holder.date.setText(events.getDate());
    holder.time.setText(events.getTime());
    holder.remb.setText(events.getRemb());
}
@Override
public int getItemCount() {
    return list.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder{
    TextView id, plan, note, date, time, remb;
    public MyViewHolder(@NonNull View itemView) {
        super(itemView);
        id = itemView.findViewById(R.id.tvIdCard);
        plan = itemView.findViewById(R.id.tvPlanCard);
        note = itemView.findViewById(R.id.tvNoteCard);
        date = itemView.findViewById(R.id.tvDateCard);
        time = itemView.findViewById(R.id.tvTimeCard);
        remb = itemView.findViewById(R.id.tvRememberCard);
    }
}

events.java

public class AllEvents extends AppCompatActivity {
RecyclerView recyclerView;
ArrayList<Events> list;
DatabaseReference dbRef;
MyAdapter adapter;

@Override
public void onBackPressed() {
    super.onBackPressed();
    startActivity(new Intent(AllEvents.this, MainActivity.class));
    finish();
}

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

    recyclerView = findViewById(R.id.recycleView);
    dbRef = FirebaseDatabase.getInstance().getReference("Events");
    list = new ArrayList<>();
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    adapter = new MyAdapter(this, list);
    recyclerView.setAdapter(adapter);
    dbRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            for(DataSnapshot dataSnapshot: snapshot.getChildren()){
                Events events = dataSnapshot.getValue(Events.class);
                list.add(events);
            }
            adapter.notifyDataSetChanged();
        }

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

        }
    });
}
}

我的

public class Events {
String id;
String plan;
String note;
String date;
String time;
String remb;

public Events(String id, String plan, String note, String date, String time, String remb) {
    this.id = id;
    this.plan = plan;
    this.note = note;
    this.date = date;
    this.time = time;
    this.remb = remb;
}
public String getId() {
    return id;
}
public void setId(String id) {
    this.id = id;
}
public String getPlan() {
    return plan;
}
public void setPlan(String plan) {
    this.plan = plan;
}
public String getNote() {
    return note;
}
public void setNote(String note) {
    this.note = note;
}
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 getRemb() {
    return remb;
}
public void setRemb(String remb) {
    this.remb = remb;
}
}

数据库是： 态

Answer 1

首先尝试使它们成为event类的私人。

private String id;
private String plan;
private String note;
private String date;
private String time;
private String remb;

其次，更改adapter =新的myadapter（this，list）;行到此处。此外，您还需要处理oncancelled时。

dbRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot snapshot) {
        for(DataSnapshot dataSnapshot: snapshot.getChildren()){
            Events events = dataSnapshot.getValue(Events.class);
            list.add(events);
        }
        adapter = new MyAdapter(this, list);
        adapter.notifyDataSetChanged();
    }

    @Override
    public void onCancelled(@NonNull DatabaseError error) {
        Log.i("???", "onCancelled Error: " + error.getMessage());
    }
});