Why does Retrofit enqueue produce null point exception?

Question

I have created my own test JSON and try to incorporate it into my Android app using Retrofit but for some reason I can´t seem to understand I get a Null Point Exception when trying to fetch the JSON.

I have created JSON that looks something like this:

[{"date":"2019/01/01","availability":"available"},{"date":"2019/01/02","availability":"closed"},{"date":"2019/01/03","availability":"closed"}]

And so on...

Then I have set up both the Retrofit code and the Room database code.

Here is the Retrofit code from the main class:

public class MainActivity extends AppCompatActivity {

MainRepository mainRepository;
Call<List<RFVariables>> getRFPosts;

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

    getRFPosts = mainRepository.getGetPosts();

    getRFPosts.enqueue( new Callback<List<RFVariables>>() {
        @Override
        public void onResponse(Call<List<RFVariables>> call, Response<List<RFVariables>> response) {
            List<RFVariables> myResponse = response.body();

            if(myResponse != null) {
                for(RFVariables item: myResponse) {
                    Log.d("TAG", item.getDate());

                }
            }

        }

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

        }
    } );

It crashes on the getRFPosts = mainRepository.getGetPosts(); line with the error Attempt to invoke interface method 'void retrofit2.Call.enqueue(retrofit2.Callback)' on a null object reference at com.slothmode.sunnyatsea.MainActivity.onCreate(MainActivity.java:25)

The repository code looks like this:

private Retrofit retrofitObject;
private RFCalls retrofitRepository;
private Call<List<RFVariables>> getPosts;

public MainRepository(Application application) {
    this.retrofitObject = new Retrofit.Builder()
            .baseUrl( "https://api.myjson.com/bins/" )
            .addConverterFactory( GsonConverterFactory.create() )
            .build();

    this.retrofitRepository = this.retrofitObject.create( RFCalls.class );
    this.getPosts = this.retrofitRepository.findPosts();
}

public Call<List<RFVariables>> getGetPosts() {
    return getPosts;
}

I have done this successfully before, so not sure what's mising this time around. Seems like an exact replica of my other successful projects. What am I missing? Let me know if there is more code I should show. Thanks in advance. Really stuck here.

You'll need to initialize your `MainRepository`. Something like `mainRepository = MainRepository(getApplicationContext());` before API call. — Jeel Vankhede, Jun 07 '19 at 07:21
show the exception stacktrace and show the line of code where it happens — Vladyslav Matviienko, Jun 07 '19 at 07:21

score 0 · Accepted Answer · answered Jun 07 '19 at 07:26

0

You've not initialized your MainRepository before doing this:

getRFPosts = mainRepository.getGetPosts();

So, initialize your mainRepository class before trying to use it.

mainRepository = new MainRepository(getApplicationContext());

See more about NullPointerException here:

How to fix NullPointerException?

answered Jun 07 '19 at 07:26

Vedprakash Wagh

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Awesome! It worked like a charm. Such a small thing I missed! Thanks alot. Really appriciate it! – Mark Tornej Jun 07 '19 at 08:02

Why does Retrofit enqueue produce null point exception?

1 Answers1