استفاده از Retrofit در ViewModel اندروید

dependencies {
 
implementation fileTree(include: ['*.jar'], dir: 'libs')
 
implementation 'com.android.support:appcompat-v7:27.1.1'
 
implementation 'com.android.support.constraint:constraint-layout:1.1.0'
 
testImplementation 'junit:junit:4.12'
 
androidTestImplementation 'com.android.support.test:runner:1.0.2'
 
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
 
//adding dependencies
 
implementation 'com.android.support:recyclerview-v7:27.1.1'
 
implementation 'com.squareup.retrofit2:retrofit:2.4.0'
 
implementation 'com.squareup.retrofit2:converter-gson:2.4.0'
 
 
implementation 'com.github.bumptech.glide:glide:4.3.1'
 
annotationProcessor 'com.github.bumptech.glide:compiler:4.3.1'
 
 
implementation "android.arch.lifecycle:extensions:1.1.0"
 
implementation "android.arch.lifecycle:viewmodel:1.1.0"
 
}

package com.example.belalkhan.androidviewmodel;
 
public class Hero {
 
private String name;
 
private String realname;
 
private String team;
 
private String firstappearance;
 
private String createdby;
 
private String publisher;
 
private String imageurl;
 
private String bio;
 
public Hero(String name, String realname, String team, String firstappearance, String createdby, String publisher, String imageurl, String bio) {
 
this.name = name;
 
this.realname = realname;
 
this.team = team;
 
this.firstappearance = firstappearance;
 
this.createdby = createdby;
 
this.publisher = publisher;
 
this.imageurl = imageurl;
 
this.bio = bio;
 
}
 
public String getName() {
 
return name;
 
}
 
public String getRealname() {
 
return realname;
 
}
 
public String getTeam() {
 
return team;
 
}
 
public String getFirstappearance() {
 
return firstappearance;
 
}
 
public String getCreatedby() {
 
return createdby;
 
}
 
public String getPublisher() {
 
return publisher;
 
}
 
public String getImageurl() {
 
return imageurl;
 
}
 
public String getBio() {
 
return bio;
 
}
 
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
  
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
  
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
  
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="200dp" />
  
    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAlignment="center"
        android:textAppearance="@style/Base.TextAppearance.AppCompat.Large" />
  
</LinearLayout>

package com.example.belalkhan.androidviewmodel;
  
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
  
import com.bumptech.glide.Glide;
  
import java.util.List;
  
public class HeroesAdapter extends RecyclerView.Adapter<HeroesAdapter.HeroViewHolder> {
  
    Context mCtx;
    List<Hero> heroList;
  
    public HeroesAdapter(Context mCtx, List<Hero> heroList) {
        this.mCtx = mCtx;
        this.heroList = heroList;
    }
  
    @NonNull
    @Override
    public HeroViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mCtx).inflate(R.layout.recyclerview_layout, parent, false);
        return new HeroViewHolder(view);
    }
  
    @Override
    public void onBindViewHolder(@NonNull HeroViewHolder holder, int position) {
        Hero hero = heroList.get(position);
  
        Glide.with(mCtx)
                .load(hero.getImageurl())
                .into(holder.imageView);
  
        holder.textView.setText(hero.getName());
    }
  
    @Override
    public int getItemCount() {
        return heroList.size();
    }
  
    class HeroViewHolder extends RecyclerView.ViewHolder {
  
        ImageView imageView;
        TextView textView;
  
        public HeroViewHolder(View itemView) {
            super(itemView);
  
            imageView = itemView.findViewById(R.id.imageView);
            textView = itemView.findViewById(R.id.textView);
        }
    }
}

public class MainActivity extends AppCompatActivity {
  
    RecyclerView recyclerView;
    HeroesAdapter adapter;
  
    List<Hero> heroList;
  
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
  
        recyclerView = findViewById(R.id.recyclerview);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
    }
}

package com.example.belalkhan.androidviewmodel;
  
import java.util.List;
  
import retrofit2.Call;
import retrofit2.http.GET;
  
public interface Api {
  
    String BASE_URL = "https://simplifiedcoding.net/demos/";
  
    @GET("marvel")
    Call<List<Hero>> getHeroes();
}

package com.example.belalkhan.androidviewmodel;
  
import android.arch.lifecycle.LiveData;
import android.arch.lifecycle.MutableLiveData;
import android.arch.lifecycle.ViewModel;
import android.widget.Toast;
  
import java.util.List;
  
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
  
public class HeroesViewModel extends ViewModel {
  
    //this is the data that we will fetch asynchronously 
    private MutableLiveData<List<Hero>> heroList;
  
    //we will call this method to get the data
    public LiveData<List<Hero>> getHeroes() {
        //if the list is null 
        if (heroList == null) {
            heroList = new MutableLiveData<List<Hero>>();
            //we will load it asynchronously from server in this method
            loadHeroes();
        }
         
        //finally we will return the list
        return heroList;
    }
  
     
    //This method is using Retrofit to get the JSON data from URL 
    private void loadHeroes() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(Api.BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();
  
        Api api = retrofit.create(Api.class);
        Call<List<Hero>> call = api.getHeroes();
  
  
        call.enqueue(new Callback<List<Hero>>() {
            @Override
            public void onResponse(Call<List<Hero>> call, Response<List<Hero>> response) {
                 
                //finally we are setting the list to our MutableLiveData
                heroList.setValue(response.body());
            }
  
            @Override
            public void onFailure(Call<List<Hero>> call, Throwable t) {
  
            }
        });
    }
}

HeroesViewModel model = ViewModelProviders.of(this).get(HeroesViewModel.class);
  
        model.getHeroes().observe(this, new Observer<List<Hero>>() {
            @Override
            public void onChanged(@Nullable List<Hero> heroList) {
                adapter = new HeroesAdapter(MainActivity.this, heroList);
                recyclerView.setAdapter(adapter);
            }
        });