Retrofit does not return a response + Null Object Reference

Question

I am new to Retrofit and was trying to build an Android App to make REST queries to my Servlet running on LocalHost.

I am aware that such an error is caused by incorrect POJOs receiving the JSON response via Retrofit. I fixed my POJOs according to my JSON response with the help of this.

But unfortunately, the error remains. All help is appreciated.

JSON Response

{"businesses":[{"business_name":"Starbucks","city":"San Francisco","avg.rating":2.0,"neighbourhood":"SOMA","latitude":10.02203,"state":"CA","type":"restaurant","business_id":"2","longitude":10.02203}]}

Businesses Class

public class Businesses {

@SerializedName("businesses")
@Expose
private List<Business> businesses = null;

public Businesses() {}

public Businesses(List<Business> businesses) {
    super();
    this.businesses = businesses;
}

public List<Business> getBusinesses() {
    return businesses;
}

public void setBusinesses(List<Business> businesses) {
    this.businesses = businesses;
}
}

Business Class

 public class Business {

@SerializedName("business_name")
@Expose
private String businessName;
@SerializedName("city")
@Expose
private String city;
@SerializedName("avg.rating")
@Expose
private float avgRating;
@SerializedName("neighbourhood")
@Expose
private String neighbourhood;
@SerializedName("latitude")
@Expose
private Double latitude;
@SerializedName("state")
@Expose
private String state;
@SerializedName("type")
@Expose
private String type;
@SerializedName("business_id")
@Expose
private String businessId;
@SerializedName("longitude")
@Expose
private Double longitude;

public Business() {
}

/**
 *
 * @param businessName
 * @param state
 * @param longitude
 * @param businessId
 * @param latitude
 * @param type
 * @param avgRating
 * @param neighbourhood
 * @param city
 */
public Business(String businessName, String city, float avgRating, String neighbourhood, Double latitude, String state, String type, String businessId, Double longitude) {
    super();
    this.businessName = businessName;
    this.city = city;
    this.avgRating = avgRating;
    this.neighbourhood = neighbourhood;
    this.latitude = latitude;
    this.state = state;
    this.type = type;
    this.businessId = businessId;
    this.longitude = longitude;
}

public String getBusinessName() {
    return businessName;
}

public void setBusinessName(String businessName) {
    this.businessName = businessName;
}

public String getCity() {
    return city;
}

public void setCity(String city) {
    this.city = city;
}

public float getAvgRating() {
    return avgRating;
}

public void setAvgRating(float avgRating) {
    this.avgRating = avgRating;
}

public String getNeighbourhood() {
    return neighbourhood;
}

public void setNeighbourhood(String neighbourhood) {
    this.neighbourhood = neighbourhood;
}

public Double getLatitude() {
    return latitude;
}

public void setLatitude(Double latitude) {
    this.latitude = latitude;
}

public String getState() {
    return state;
}

public void setState(String state) {
    this.state = state;
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

public String getBusinessId() {
    return businessId;
}

public void setBusinessId(String businessId) {
    this.businessId = businessId;
}

public Double getLongitude() {
    return longitude;
}

public void setLongitude(Double longitude) {
    this.longitude = longitude;
}

}

Logcat

FATAL EXCEPTION: main
Process: mdnaseemashraf.yapapp, PID: 20528
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at mdnaseemashraf.yapapp.BusinessActivity$1.onResponse(BusinessActivity.java:73)
at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:70)
at android.os.Handler.handleCallback(Handler.java:743)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:171)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

My Recycler Adapter

public class BusinessRecyclerAdapter extends RecyclerView.Adapter<BusinessRecyclerAdapter.BusinessViewHolder> {

private Businesses yapBusinesses;

public class BusinessViewHolder extends RecyclerView.ViewHolder
{
    public TextView tvBusinessName, tvType, tvCity;
    public RatingBar ratingBar;

    public BusinessViewHolder(View itemView) {
        super(itemView);

        tvBusinessName = (TextView) itemView.findViewById(R.id.tvBusinessName);
        tvType = (TextView) itemView.findViewById(R.id.tvType);
        tvCity = (TextView) itemView.findViewById(R.id.tvCity);
        ratingBar = (RatingBar) itemView.findViewById(R.id.ratingBar);
    }
}

public BusinessRecyclerAdapter(Businesses yapBusinessesIn)
{
    this.yapBusinesses = yapBusinessesIn;
}

@Override
public BusinessRecyclerAdapter.BusinessViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
{
    View itemView = LayoutInflater.from(parent.getContext())
                                  .inflate(R.layout.list_item_business, parent, false);

    return new BusinessViewHolder(itemView);
}

@Override
public void onBindViewHolder(BusinessRecyclerAdapter.BusinessViewHolder holder, int position)
{
    Business yapBusiness =   yapBusinesses.getBusinesses().get(position);
    holder.tvBusinessName.setText(yapBusiness.getBusinessName());
    holder.tvBusinessName.setText(yapBusiness.getBusinessName());
    holder.tvBusinessName.setText(yapBusiness.getBusinessName());
    holder.ratingBar.setRating(yapBusiness.getAvgRating());
}

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

BusinessActivity

public class BusinessActivity extends AppCompatActivity {

private Businesses yapBusinesses = new Businesses();
private RecyclerView businessRecyclerView;
private BusinessRecyclerAdapter businessRecyclerAdapter;

//RETROFIT
public static final String BASE_URL = "http://192.168.1.4:8080/Yap/";
private static Retrofit retrofit = null;

private final static int APP_ID = 11;
private final static String REQUEST_TYPE = "search";
private final static String FORM = "strict"; //"lenient" or "strict",
private final static String KEYWORDS = "sta";
private final static String CITY = "San";
private final static String STATE = "C";
private final static String TYPE = "restaurant"; //"restaurant", "shop", "hotel", "cafe" & "bar".
//

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

    businessRecyclerView = (RecyclerView) findViewById(R.id.business_recycler_view);

    RecyclerView.LayoutManager businesslayoutManager = new LinearLayoutManager(getApplicationContext());
    businessRecyclerView.setLayoutManager(businesslayoutManager);

    businessRecyclerView.setItemAnimator(new DefaultItemAnimator());

    connectAndGetApiData();
}

public void connectAndGetApiData(){

    if (retrofit == null) {
        retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    }

    YapApiService yapApiService = retrofit.create(YapApiService.class);

    Call<BusinessResponse> call = yapApiService.getSearchedBusiness(APP_ID, REQUEST_TYPE, FORM,
                                                                    KEYWORDS, CITY, STATE, TYPE);
    call.enqueue(new Callback<BusinessResponse>() {
        @Override
        public void onResponse(Call<BusinessResponse> call, Response<BusinessResponse> response) {

            Businesses businessesIN = response.body().getResults();

            Log.println(Log.INFO, "Response Body", response.body().toString()); //Response Body: mdnaseemashraf.yapapp.BusinessResponse@557a8c2
            Log.println(Log.INFO, "Response Results", response.body().getResults().toString()); //Shows NUll ERROR - No Results?

            businessRecyclerView.setAdapter(new BusinessRecyclerAdapter(businessesIN));

            Log.d("Retrofit Data Tag", "Number of Businesses received: " + businessesIN.getBusinesses().size());

            businessRecyclerView.getAdapter().notifyDataSetChanged();
        }

        @Override
        public void onFailure(Call<BusinessResponse> call, Throwable throwable) {
            Log.e("Retrofit Data Error", throwable.toString());
        }
    });
}
}

BusinessResponse Class

public class BusinessResponse
{
@SerializedName("page")
private int page;
@SerializedName("results")
private Businesses results;
@SerializedName("total_results")
private int totalResults;
@SerializedName("total_pages")
private int totalPages;

public int getPage() {
    return page;
}

public void setPage(int page) {
    this.page = page;
}

public Businesses getResults() {
    return results;
}

public void setResults(Businesses results) {
    this.results = results;
}

public int getTotalResults() {
    return totalResults;
}

public void setTotalResults(int totalResults) {
    this.totalResults = totalResults;
}

public int getTotalPages() {
    return totalPages;
}

public void setTotalPages(int totalPages) {
    this.totalPages = totalPages;
}
}

It will be helpful to see how you create `BusinessRecyclerAdapter` objects. — Titus, Sep 23 '17 at 08:32
Added my Business Activity class which uses the fetched data from onResponse to build Businesses object and further uses it to build new adapter, setting this new adapter to the recycle view. — MD Naseem Ashraf, Sep 23 '17 at 08:42
@EJP Did not find any relevant to my problem of non-responsive Retrofit. — MD Naseem Ashraf, Sep 23 '17 at 09:30
Fixed the issue. Retrofit Response class was built incorrectly as well as POJOs used in the project. — MD Naseem Ashraf, Sep 23 '17 at 10:44

score 0 · Answer 1 · answered Sep 23 '17 at 08:45

I think this statement is causing the exception businessRecyclerAdapter = new BusinessRecyclerAdapter(yapBusinesses);. When this is executed, the businesses variable of the yapBusinesses object is null.

Just remove that statement and the businessRecyclerView.setAdapter(businessRecyclerAdapter); statement from the onCreate method. That should get rid of the exception.

akhilesh0707 · Answer 2 · 2017-09-23T08:58:30.207

0

Inside your yapBusinesses business list is null at the time of initializing new BusinessRecyclerAdapter(yapBusinesses);

Perform null check on your BusinessRecyclerAdapter adapter getItemCount() method

This will solve your problem, try below code

@Override
public int getItemCount() {
    if(yapBusinesses.getBusinesses()!=null){
      return yapBusinesses.getBusinesses().size();
    }else{
      return 0;
    }
}

edited Sep 23 '17 at 08:58

answered Sep 23 '17 at 08:51

akhilesh0707

6,709
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A null check is not the issues here, as I see. There is no response from Retrofit. Even the Log gives a null error. The businessesIN response is not returned, as far as I can guess. – MD Naseem Ashraf Sep 23 '17 at 09:09
Please check the error log it is clearly showing that your `yapBusinesses.getBusinesses()` is null – akhilesh0707 Sep 23 '17 at 09:12
Yes. Updating all logs and files without the null initializations. Wait a minute. – MD Naseem Ashraf Sep 23 '17 at 09:15
Updated everything Retrofit response does not have any results. As shown in code and log. – MD Naseem Ashraf Sep 23 '17 at 09:28
try to put a breakpoint and debug your code – akhilesh0707 Sep 23 '17 at 09:33
Thanks, guv. The issue was primarily of Retrofit, found that my POJOs were not built correctly. Especially, my response object class. – MD Naseem Ashraf Sep 23 '17 at 10:46

Retrofit does not return a response + Null Object Reference

2 Answers2