MVVM implementation (JAVA)

build.gradle

dependencies {
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.core:core-ktx:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.1.0'
}

SampleListFragment.java

public class ListFragment extends Fragment {

    private SampleViewModel mViewModel;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_sample_list, container, false);
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        mViewModel = ViewModelProviders.of(this).get(SampleViewModel.class);
        mViewModel.mResponseLiveData.observe(getViewLifecycleOwner(), new Observer<ModelResponse>() {
            @Override
            public void onChanged(ModelResponse response) {
                if (response != null) {
                    progressbar.setVisibility(View.GONE);
                    // Update UI based on response
                }
            }
        });

        fetchSampleList();
    }

    private void fetchSampleList() {
        progressbar.setVisibility(View.VISIBLE);
        mViewModel.fetchData();
    }
}

SampleViewModel.java

import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;

public class ListViewModel extends ViewModel {
    public MutableLiveData<ModelResponse> mResponseLiveData = new MutableLiveData<>();

    public void fetchData() {
        APISample objApiSample = APIRetroBuilder.getRetroBuilder(this, false).create(APISample.class);
        Call<ModelResponse> callModelSampleRes = objApiSample.callSampleListApi();
        callModelSampleRes.enqueue(new Callback<ModelResponse>() {
            @Override
            public void onResponse(Call<ModelResponse> call, Response<ModelResponse> response) {

                if (response.isSuccessful()) {
                    if (response.body() != null) {
                        mContentLiveData.setValue(response.body());
                    }
                }
            }

            @Override
            public void onFailure(Call<ModelResponse> call, Throwable t) {

            }
        });
    }
}