我无法从我的firebaseddatabase中获取值

Question

当我运行程序时，我得到这个错误:com.cdirect.agenda2.AllEvents ondatachange 1.美元(AllEvents.java: 47)-Events events = dataSnapshot.getValue(Events.class);

我想从我的firebaseddatabase获得所有数据。我创建了Events.java。它有getter和setter。MyAdapter正在适应AllEvents.java上的RecyclerView。我想在AllEvents.java上显示所有数据。但我不能成功。你能帮我吗?

MyAdapter.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);
}
}

MyEvents.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) {
}
});
}
}

Events.java

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;
}
}

My Database is:输入图片描述

Answer 1

首先尝试使它们为Event类私有。

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

第二，将adapter = new MyAdapter(this, list);行改为此处。另外，当onCancelled也需要处理。

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());
}
});