GSON melempar "Diharapkan BEGIN_OBJECT tetapi apakah BEGIN_ARRAY"?

Saya mencoba mengurai string JSON seperti ini

[
   {
      "updated_at":"2012-03-02 21:06:01",
      "fetched_at":"2012-03-02 21:28:37.728840",
      "description":null,
      "language":null,
      "title":"JOHN",
      "url":"http://rus.JOHN.JOHN/rss.php",
      "icon_url":null,
      "logo_url":null,
      "id":"4f4791da203d0c2d76000035",
      "modified":"2012-03-02 23:28:58.840076"
   },
   {
      "updated_at":"2012-03-02 14:07:44",
      "fetched_at":"2012-03-02 21:28:37.033108",
      "description":null,
      "language":null,
      "title":"PETER",
      "url":"http://PETER.PETER.lv/rss.php",
      "icon_url":null,
      "logo_url":null,
      "id":"4f476f61203d0c2d89000253",
      "modified":"2012-03-02 23:28:57.928001"
   }
]

ke dalam daftar objek.

List<ChannelSearchEnum> lcs = (List<ChannelSearchEnum>) new Gson().fromJson( jstring , ChannelSearchEnum.class);

Ini kelas objek yang saya gunakan.

import com.google.gson.annotations.SerializedName;

public class ChannelSearchEnum {



@SerializedName("updated_at")
private String updated_at;

@SerializedName("fetched_at")
private String fetched_at;

@SerializedName("description")
private String description;

@SerializedName("language")
private String language;

@SerializedName("title")
private String title;

@SerializedName("url")
private String url;

@SerializedName("icon_url")
private String icon_url;

@SerializedName("logo_url")
private String logo_url;

@SerializedName("id")
private String id;

@SerializedName("modified")
private String modified;

public final String get_Updated_at() {
    return this.updated_at;
}

public final String get_Fetched_at() {
    return this.fetched_at;
}

public final String get_Description() {
    return this.description;
}

public final String get_Language() {
    return this.language;
}

public final String get_Title() {
    return this.title;
}

public final String get_Url() {
    return this.url;
}

public final String get_Icon_url() {
    return this.icon_url;
}

public final String get_Logo_url() {
    return this.logo_url;
}

public final String get_Id() {
    return this.id;
}

public final String get_Modified() {
    return this.modified;
}

        }

Tapi itu membuatku senang

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2

Ada ide bagaimana saya harus memperbaikinya?

Masalahnya adalah Anda mengatakan GsonAnda memiliki objek tipe Anda. Kamu tidak. Anda memiliki berbagai objek tipe Anda. Anda tidak bisa hanya mencoba dan memberikan hasil seperti itu dan berharap itu bekerja secara ajaib;)

Panduan pengguna untuk GsonMenjelaskan cara menangani ini:

https://github.com/google/gson/blob/master/UserGuide.md

Ini akan berhasil:

ChannelSearchEnum[] enums = gson.fromJson(yourJson, ChannelSearchEnum[].class);

Tapi ini lebih baik:

Type collectionType = new TypeToken<Collection<ChannelSearchEnum>>(){}.getType();
Collection<ChannelSearchEnum> enums = gson.fromJson(yourJson, collectionType);

Masalahnya adalah Anda meminta objek bertipe ChannelSearchEnumtetapi yang sebenarnya Anda miliki adalah objek bertipe List<ChannelSearchEnum>.

Anda dapat mencapai ini dengan:

Type collectionType = new TypeToken<List<ChannelSearchEnum>>(){}.getType();
List<ChannelSearchEnum> lcs = (List<ChannelSearchEnum>) new Gson()
               .fromJson( jstring , collectionType);

Dalam string JSON kasus saya:

[{"category":"College Affordability",
  "uid":"150151",
  "body":"Ended more than $60 billion in wasteful subsidies for big banks and used the savings to put the cost of college within reach for more families.",
  "url":"http:\/\/www.whitehouse.gov\/economy\/middle-class\/helping middle-class-families-pay-for-college",
  "url_title":"ending subsidies for student loan lenders",
  "type":"Progress",
  "path":"node\/150385"}]

dan saya mencetak "kategori" dan "url_title" di recycleview

Datum.class

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Datum {
@SerializedName("category")
@Expose
private String category;
@SerializedName("uid")
@Expose
private String uid;
@SerializedName("url_title")
@Expose
private String urlTitle;

/**
 * @return The category
 */
public String getCategory() {
    return category;
}

/**
 * @param category The category
 */
public void setCategory(String category) {
    this.category = category;
}

/**
 * @return The uid
 */
public String getUid() {
    return uid;
}

/**
 * @param uid The uid
 */
public void setUid(String uid) {
    this.uid = uid;
}

/**
 * @return The urlTitle
 */
public String getUrlTitle() {
    return urlTitle;
}

/**
 * @param urlTitle The url_title
 */
public void setUrlTitle(String urlTitle) {
    this.urlTitle = urlTitle;
}

}

Minta Permukaan

import java.util.List;

import retrofit2.Call;
import retrofit2.http.GET;

/**
 * Created by Shweta.Chauhan on 13/07/16.
 */

public interface RequestInterface {

   @GET("facts/json/progress/all")
   Call<List<Datum>> getJSON();
}

DataAdapter

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

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

/**
 * Created by Shweta.Chauhan on 13/07/16.
 */

public class DataAdapter extends RecyclerView.Adapter<DataAdapter.MyViewHolder>{

private Context context;
private List<Datum> dataList;

public DataAdapter(Context context, List<Datum> dataList) {
    this.context = context;
    this.dataList = dataList;
}

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

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    holder.categoryTV.setText(dataList.get(position).getCategory());
    holder.urltitleTV.setText(dataList.get(position).getUrlTitle());

}

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

public class MyViewHolder extends RecyclerView.ViewHolder{

    public TextView categoryTV, urltitleTV;

    public MyViewHolder(View itemView) {
        super(itemView);
        categoryTV = (TextView) itemView.findViewById(R.id.txt_category);
        urltitleTV = (TextView)     itemView.findViewById(R.id.txt_urltitle);
    }
}
}

dan akhirnya MainActivity.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {

private RecyclerView recyclerView;
private DataAdapter dataAdapter;
private List<Datum> dataArrayList;

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

private void initViews(){
    recyclerView=(RecyclerView) findViewById(R.id.recycler_view);
    recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
    loadJSON();
}

private void loadJSON(){
    dataArrayList = new ArrayList<>();
    Retrofit retrofit=new Retrofit.Builder().baseUrl("https://www.whitehouse.gov/").addConverterFactory(GsonConverterFactory.create()).build();
    RequestInterface requestInterface=retrofit.create(RequestInterface.class);
    Call<List<Datum>> call= requestInterface.getJSON();
    call.enqueue(new Callback<List<Datum>>() {
        @Override
        public void onResponse(Call<List<Datum>> call, Response<List<Datum>> response) {
            dataArrayList = response.body();
            dataAdapter=new DataAdapter(getApplicationContext(),dataArrayList);
            recyclerView.setAdapter(dataAdapter);
        }

        @Override
        public void onFailure(Call<List<Datum>> call, Throwable t) {
            Log.e("Error",t.getMessage());
        }
    });
}
}

Alternatifnya bisa

untuk membuat respons Anda terlihat seperti

myCustom_JSONResponse

{"master":[
   {
      "updated_at":"2012-03-02 21:06:01",
      "fetched_at":"2012-03-02 21:28:37.728840",
      "description":null,
      "language":null,
      "title":"JOHN",
      "url":"http://rus.JOHN.JOHN/rss.php",
      "icon_url":null,
      "logo_url":null,
      "id":"4f4791da203d0c2d76000035",
      "modified":"2012-03-02 23:28:58.840076"
   },
   {
      "updated_at":"2012-03-02 14:07:44",
      "fetched_at":"2012-03-02 21:28:37.033108",
      "description":null,
      "language":null,
      "title":"PETER",
      "url":"http://PETER.PETER.lv/rss.php",
      "icon_url":null,
      "logo_url":null,
      "id":"4f476f61203d0c2d89000253",
      "modified":"2012-03-02 23:28:57.928001"
   }
]
}

dari pada

server_JSONResponse

[
   {
      "updated_at":"2012-03-02 21:06:01",
      "fetched_at":"2012-03-02 21:28:37.728840",
      "description":null,
      "language":null,
      "title":"JOHN",
      "url":"http://rus.JOHN.JOHN/rss.php",
      "icon_url":null,
      "logo_url":null,
      "id":"4f4791da203d0c2d76000035",
      "modified":"2012-03-02 23:28:58.840076"
   },
   {
      "updated_at":"2012-03-02 14:07:44",
      "fetched_at":"2012-03-02 21:28:37.033108",
      "description":null,
      "language":null,
      "title":"PETER",
      "url":"http://PETER.PETER.lv/rss.php",
      "icon_url":null,
      "logo_url":null,
      "id":"4f476f61203d0c2d89000253",
      "modified":"2012-03-02 23:28:57.928001"
   }
]

KODE

  String server_JSONResponse =.... // the string in which you are getting your JSON Response after hitting URL
String myCustom_JSONResponse="";// in which we will keep our response after adding object element to it
     MyClass apiResponse = new MyClass();

     myCustom_JSONResponse="{\"master\":"+server_JSONResponse+"}";



    apiResponse = gson.fromJson(myCustom_JSONResponse, MyClass .class);

Setelah ini akan menjadi yang lainnya GSON Parsing

menurut panduan Pengguna GSON , Anda tidak bisa.

Keterbatasan Koleksi

Dapat membuat serial koleksi benda yang sewenang-wenang tetapi tidak dapat membatalkan deserialisasi darinya. Karena tidak ada cara bagi pengguna untuk menunjukkan jenis objek yang dihasilkan

Ini terlihat seperti daftar array Json. Oleh karena itu yang terbaik digunakan ArrayListuntuk menangani data. Di titik akhir api Anda, tambahkan daftar array seperti ini

 @GET("places/")
Call<ArrayList<Place>> getNearbyPlaces(@Query("latitude") String latitude, @Query("longitude") String longitude);

Anda perlu memberi tahu Gson jenis respons tambahan seperti di bawah ini

import com.google.common.reflect.TypeToken;
import java.lang.reflect.Type;


Type collectionType = new TypeToken<List<UserSite>>(){}.getType();
List<UserSite> userSites  = gson.fromJson( response.getBody() , collectionType);

Saya tidak yakin apakah ini cara terbaik untuk menggunakan GSON, tetapi bekerja untuk saya. Anda dapat menggunakan beberapa seperti ini di MainActivity:

 public void readJson() {
    dataArrayList = new ArrayList<>();
    String json = "[\n" + IOHelper.getData(this) + "\n]\n";
    Log.d(TAG, json);
    try{
        JSONArray channelSearchEnums = new JSONArray(json);

        for(int i=0; i< channelSearchEnums.length(); i++)
        {
            JSONObject enum = channelSearchEnums.getJSONObject(i);
            ChannelSearchEnum channel = new ChannelSearchEnum(
                   enum.getString("updated_at"), enum.getString("fetched_at"),
                   enum.getString("description"), enum.getString("language"),
                   enum.getString("title"), enum.getString("url"),
                   enum.getString("icon_url"), enum.getString("logo_url"),
                   enum.getString("id"), enum.getString("modified"))         

                   dataArrayList.add(channel);
        }

         //The code and place you want to show your data            

    }catch (Exception e)
    {
        Log.d(TAG, e.getLocalizedMessage());
    }
}

Anda hanya memiliki string, tetapi jika Anda memiliki dobel atau int, Anda bisa memasukkan getDoubleatau getIntjuga.

Metode IOHelperkelas adalah yang berikutnya (Di sini, path disimpan di Penyimpanan internal):

 public static String getData(Context context) {
    try {
        File f = new File(context.getFilesDir().getPath() + "/" + fileName);
        //check whether file exists
        FileInputStream is = new FileInputStream(f);
        int size = is.available();
        byte[] buffer = new byte[size];
        is.read(buffer);
        is.close();
        return new String(buffer);
    } catch (IOException e) {
        Log.e("TAG", "Error in Reading: " + e.getLocalizedMessage());
        return null;
    }
}

Jika Anda ingin informasi lebih lanjut tentang ini, Anda dapat melihat video ini , tempat saya mendapatkan kode readJson(); dan utas ini tempat saya mendapatkan kode getData().

Kotlin:

var list=ArrayList<Your class name>()
val listresult: Array<YOUR CLASS NAME> = Gson().fromJson(
                YOUR JSON RESPONSE IN STRING,
                Array<Your class name>:: class.java)

list.addAll(listresult)