Question

我使用recyclerview显示来自firebase的数据。我使用了一个arraylist来存储他们来自firebase的键值，然后使用该数组列表填充了回收站视图但这里的问题是键值没有被添加到列表中但是当我使用toast时显示其工作正常的关键值。我犯的错误是什么？如何解决？

package com.sabari.inventory;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

import java.util.ArrayList;
import java.util.List;


public class MainActivity extends AppCompatActivity implements MyAdapter.ClickListener{

RecyclerView recyclerView;
MyAdapter adapter;
List<Info> infos;
DatabaseReference myRef,dr;
List<String> tit,d;
int position;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    recyclerView = (RecyclerView) findViewById(R.id.myRecView);
    tit = new ArrayList<>();
    d = new ArrayList<>();

    myRef = FirebaseDatabase.getInstance().getReference();
    dr = myRef.child("Machines");
    adapter = new MyAdapter(getApplicationContext(),getData());
    adapter.setClickListener(this);
    recyclerView.setAdapter(adapter);
    recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));

}

public List<Info> getData(){

    infos = new ArrayList<>();
    dr.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            tit.add(dataSnapshot.getKey());
            adapter.notifyDataSetChanged();
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    for(int i=0;i<tit.size();i++) {
        Info now = new Info();
        now.title = tit.get(i);
        now.desc = "";
        infos.add(now);
    }return infos;
}

@Override
public void itemClicked(View view, int position) {
        MyDialog myDialog = new MyDialog();
        myDialog.show(getSupportFragmentManager(),"");

}
}

信息类

package com.sabari.inventory;



public class Info {

int img;
String title;
String desc;
}

适配器类

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyVH>  {

LayoutInflater layoutInflater;
Context context;
ClickListener clickListener;
List<Info> infoList = Collections.emptyList();
public MyAdapter(Context context,List<Info> infoList) {
    layoutInflater=LayoutInflater.from(context);
    this.infoList = infoList;
    this.context=context;
}

@Override
public MyVH onCreateViewHolder(ViewGroup parent, int viewType) {
    View view=layoutInflater.inflate(R.layout.single_row,parent,false);
    MyVH myVH = new MyVH(view);
    return myVH;
}

@Override
public void onBindViewHolder(MyVH holder, final int position) {
    Info now = infoList.get(position);
    holder.textView1.setText(now.title);
    holder.textView2.setText(now.desc);
}

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

public void setClickListener(ClickListener clickListener)
{
    this.clickListener=clickListener;
}



class MyVH extends RecyclerView.ViewHolder implements View.OnClickListener{

    ImageView imageView;
    TextView textView1,textView2;
    public MyVH(View itemView) {
        super(itemView);
        imageView = (ImageView) itemView.findViewById(R.id.imageView);
        textView1 = (TextView) itemView.findViewById(R.id.textView);
        textView2 = (TextView) itemView.findViewById(R.id.textView2);

        itemView.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if(clickListener!=null)
        {
            clickListener.itemClicked(view,getPosition());
        }
    }
}

public interface ClickListener{
    public void itemClicked(View view,int position);

}
}

修改了getData（）方法

 public List<Info> getData(){

    infos = new ArrayList<>();

    dr.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            Info info= dataSnapshot.getValue(Info.class);
            tit.add(info.getTitle());
            adapter.notifyDataSetChanged();
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    for(int i=0;i<1;i++) {
        Info now = new Info();
        now.title = tit.get(i);
        now.desc = "";
        infos.add(now);
    }return infos;
}

Answer 1

将Info.class创建为Object：

public class Info {

int img;
String title;
String desc;

public Info() {};

public Info(int img, String title, String desc) {
    this.img = img;
    this.title = title;
    this.desc = desc;
}
public int getImg() { return img; }
public String getTitle() { return title; }
public String getDesc() { return desc; }
}

在你的听众中

@Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        Info info = dataSnapshot.getValue(Info.class);
        tit.add(info.getTitle());
        adapter.notifyDataSetChanged();
    }

Answer 2

在onChildAdded()方法中执行此操作，tit和d不是必需的：

    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        Info now = new Info();
        now.title = dataSnapshot.getKey();
        now.desc = "";
        infos.add(now);
        adapter.notifyDataSetChanged();
    }

将检索到的键值从firebase添加到arraylist不起作用

2 个答案: