Question

MaintActivity

package com.finn.aroundu;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class MainActivity extends AppCompatActivity {


RecyclerView recyclerView;
private RecyclerView mPostList;
private DatabaseReference mDatabase;




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

    mDatabase= FirebaseDatabase.getInstance().getReference();

    Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(mToolbar);
    getSupportActionBar().setDisplayShowTitleEnabled(false);

    mPostList = (RecyclerView) findViewById(R.id.post_list);
    mPostList.setHasFixedSize(true);
    if(recyclerView != null) {
        mPostList.setLayoutManager(new LinearLayoutManager(this));
    }





        }

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

    FirebaseRecyclerAdapter<Location_data,PostViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Location_data, PostViewHolder>(

            Location_data.class,
    R.layout.recycler_adpater,
    PostViewHolder.class,
            mDatabase



    ) {
        @Override
        protected void populateViewHolder(PostViewHolder viewHolder, Location_data model, int position) {

            viewHolder.setName(model.getName());
            viewHolder.setCaption(model.getCaption());
            viewHolder.setLocation(model.getLocation());
        }
    };
    mPostList.setAdapter(firebaseRecyclerAdapter);


}

public static class PostViewHolder extends RecyclerView.ViewHolder {

    View mView;

    public PostViewHolder(View itemView) {
        super(itemView);

        itemView= mView;


    }

    public void setName(String name){
        TextView info_text = (TextView) mView.findViewById(R.id.info_text);
        info_text.setText(name);

    }

    public void setCaption(String caption){

        TextView info_text2=(TextView) mView.findViewById(R.id.info_text2);
        info_text2.setText(caption);

    }

    public void setLocation(String location){

        TextView info_text3 = (TextView)mView.findViewById(R.id.info_text3);
        info_text3.setText(location);
    }


}


public boolean onCreateOptionsMenu(final Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);

    return super.onCreateOptionsMenu(menu);

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if(item.getItemId()==R.id.add){
        startActivity(new Intent(MainActivity.this,post.class));


    }


    return super.onOptionsItemSelected(item);
}
}

Location_Activity（方法）

package com.finn.aroundu;

/**
* Created by Sagar on 1/31/2017.
*/

public class Location_data {



private String Name;
private String Location;
private String Caption;

public Location_data(){

}

public Location_data(String Location, String Name, String Caption) {
    this.Location = Location;
    this.Name = Name;
    this.Caption = Caption;
}

public String getCaption() {
    return Caption;
}

public void setCaption(String Caption) {
    this.Caption = Caption;
}

public String getLocation() {
    return Location;
}

public void setLocation(String Location) {
    this.Location = Location;
}

public String getName() {
    return Name;
}

public void setName(String Name) {
    this.Name = Name;
}
}

我正在创建一个简单的应用程序来从我的firebase数据库中获取数据并将其显示在RecyclerView上，但数据根本没有提取。输出只是一个空白活动。我是应用程序开发的新手，我认为我犯了一些愚蠢的错误，请指出我的错误。

CRASH LOG：

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.finn.aroundu.Location_data

得到了修复：我的代码中有很多重大问题，我无意中忘记了从我所参考的博客编写活动代码。不管怎样，谢谢你！

Answer 1

就像异常所说的那样，你会收到字符串json响应。您需要转换为对象

https://www.learnhowtoprogram.com/android/data-persistence/firebase-recycleradapter

Answer 2

在行中检查对数据库的引用：

mDatabase= FirebaseDatabase.getInstance().getReference();

Recyclerview无法从Firebase DB获取数据

2 个答案: