View progressBar = findViewById(R.id.progress_bar);

new NetworkLoader.Builder<List<Repo>>()
  .setProgressBar(progressBar)
  .setCallback(new NetworkLoader.Callback() {
      @Override
      public void callback(NetworkWorkpiece workpiece) {
          if (isFinishing()) {
              return;
          }

          if (!workpiece.isSuccess()) {
              Toast.makeText(
                      getApplicationContext(), 
                      workpiece.getError(), 
                      Toast.LENGTH_SHORT).show();
              return;
          }
      }
  })
  .load(new NetworkWorker<List<Repo>>() {
      @Override
      public List<Repo> getWorkpiece() {
          return getApiInterface().listRepos("tonyjs");
      }
  });

private ApiInterface mApiInterface;
public ApiInterface getApiInterface() {
    if (mApiInterface == null) {
        RestAdapter adapter = new RestAdapter.Builder()
                .setEndpoint(ApiInterface.END_POINT)
                .setLogLevel(BuildConfig.DEBUG ?
                        RestAdapter.LogLevel.FULL : RestAdapter.LogLevel.BASIC)
                .build();

        mApiInterface = adapter.create(ApiInterface.class);
    }
    return mApiInterface;
}