避免重复调用CallBack <t>，Retrofit

Question

我使用Retrofit处理GitHub api的数据。在一个活动中，我需要2个引用Retrofit Builder，因此 - 2个回调。到目前为止，calss的定义是：

public class UserScreen extends Activity implements Callback<GitHubUser>, Callback<GitHubRepos>

如何避免重复的课程？我对User调用方法的定义如下：

 public void loadData(View view) {
    Gson gson = new GsonBuilder()
            .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
            .create();
     retrofit = new Retrofit.Builder()
            .baseUrl(GitHubUserAPI.ENDPOINT)
            .addConverterFactory(GsonConverterFactory.create(gson))
            .build();

    // prepare call in Retrofit 2.0
    GitHubUserAPI githubUserAPI = retrofit.create(GitHubUserAPI.class);

    Call<GitHubUser> callUser = githubUserAPI.getUser(newString);
    callUser.enqueue(this);

    Call<GitHubUser> callAvatar = githubUserAPI.getAvatar(newString);
    callAvatar.enqueue(this);

    Call<GitHubUser> callFollowers = githubUserAPI.getFollowers(newString);
    callFollowers.enqueue(this);

}


@Override
public void onResponse(Call<GitHubUser> call, final Response<GitHubUser> response) {
    final int code = response.code();
    if (code == 200) {
        final GitHubUser user = response.body();
       userNameTV.setText(user.getName());
        followersTV.setText("Followers: " + user.getFollowers());
        followingTV.setText("Following: " + user.getFollowing());



        ImageDownloader task = new ImageDownloader();
        Bitmap myImage;

        try {
            myImage = task.execute(user.getAvatar()).get();
            avatarImg.setImageBitmap(myImage);
            avatarImg.getLayoutParams().height=150;
            avatarImg.getLayoutParams().width=150;

        } catch (Exception e) {

            e.printStackTrace();

        }
    }
}

public class ImageDownloader extends AsyncTask<String, Void, Bitmap> {
    @Override
    protected Bitmap doInBackground(String... urls) {

        try {

            URL url = new URL(urls[0]);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.connect();
            InputStream inputStream = connection.getInputStream();
            Bitmap myBitmap = BitmapFactory.decodeStream(inputStream);
            return myBitmap;

        } catch (MalformedURLException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }
        return null;
    }
}

@Override
public void onFailure(Call<GitHubUser> call, Throwable t) {
    Toast.makeText(this, "Nope", Toast.LENGTH_LONG).show();

}

谢谢！