java.lang.NullPointerException : Attempt to invoke virtual method on a null object reference Retrofit

Question

我试图从 MovieGlu API 返回电影院列表，但在代码的第 98 行出现空指针异常。电影回归，我正在努力让电影院以同样的方式回归。 API 确实在 postman 中返回它们。我正在使用 Retrofit2 返回数据。

运行应用程序时出现错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List com.example.retrofitapp.model.nearbycinemas.Cinema.getCinemas()' on a null object reference Retrofit

MainActivity.class

public class MainActivity extends AppCompatActivity {
    private TextView textViewResult;

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

        textViewResult = findViewById(R.id.text_view_result);

        OkHttpClient.Builder client = new OkHttpClient.Builder();
        client.addInterceptor(new Interceptor() {
            @Override
            public okhttp3.Response intercept(Chain chain) throws IOException {
                Request request = chain.request()
                        .newBuilder()
                        .addHeader("api-version", "v200")
                        .addHeader("Authorization", "Basic *******************")
                        .addHeader("client", "WALS_1")
                        .addHeader("x-api-key", "**********************************")
                        .addHeader("device-datetime", "2018-09-14T08:30:17.360Z")
                        .addHeader("territory", "UK")
                        .addHeader("Geolocation", "****************;*************")
                        .build();
                return chain.proceed(request);
            }
        });
        Retrofit retrofit = new Retrofit.Builder()
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl("https://api-gate2.movieglu.com/")
                .client(client.build())
                .build();

        MovieGluApi movieGluApi = retrofit.create(MovieGluApi.class);
        Call<Film> filmCall = movieGluApi.getFilmNames();
        filmCall.enqueue(new Callback<Film>() {
            @Override
            public void onResponse(Call<Film> call,Response<Film> response) {
                if (!response.isSuccessful()){
                    textViewResult.setText("Code: " + response.code());
                    Log.d("dfkjf", response.toString());
                    return;
                }

                assert response.body() != null;
                List<Film> films = response.body().getFilms();
                Log.d("dfkjf", response.toString());

                for (Film film : films){
                    String content = "";
                    content += "Film ID: " + film.getFilmId() +"\n";
                    content += "IMDB ID: " + film.getImdbId() +"\n";
                    content += "Film Name: " + film.getFilmName() +"\n\n";
                    Log.d("Film name", film.toString());
                    textViewResult.append(content);
                }
            }
            @Override
            public void onFailure(Call<Film> call, Throwable t) {
                textViewResult.setText(t.getMessage());
            }
        });

        Call<Cinema> cinemaCall = movieGluApi.getNearbyCinema();
        cinemaCall.enqueue(new Callback<Cinema>() {
            @Override
            public void onResponse(Call<Cinema> call, Response<Cinema> response) {
                if (!response.isSuccessful()){
                    textViewResult.setText("Code: " + response.code());
                    Log.d("Response", "Message: " + response.toString());
                    return;
                }

                assert response.body() != null;
                List<Cinema> cinemas = response.body().getCinemas();
                Log.d("Response", "response: " + response.toString());
                for (Cinema cinema : cinemas){
                    String cinemaContent = "";
                    cinemaContent += "Cinema Name: " + cinema.getCinemaName() +"\n";
                    cinemaContent += "Cinema Address 1 " + cinema.getAddress() +"\n";
                    cinemaContent += "Cinema Address: 2 " + cinema.getAddress2() +"\n\n";
                    cinemaContent += "Cinema City: " + cinema.getCity() +"\n\n";
                    cinemaContent += "Cinema Country " + cinema.getCounty() +"\n\n";
                    cinemaContent += "Cinema PostCode: " + cinema.getPostcode() +"\n\n";
                    textViewResult.append(cinemaContent);
                }
            }

            @Override
            public void onFailure(Call<Cinema> call, Throwable t) {
                textViewResult.setText(t.getMessage());
            }
        });
    }
}

第 98 行错误

List<Cinema> cinemas = response.body().getCinemas();

cinemas.java(模型)

public class Cinema {

    @SerializedName("cinema_id")
    @Expose
    private Integer cinemaId;
    @SerializedName("cinema_name")
    @Expose
    private String cinemaName;
    @SerializedName("address")
    @Expose
    private String address;
    @SerializedName("address2")
    @Expose
    private String address2;
    @SerializedName("city")
    @Expose
    private String city;
    @SerializedName("county")
    @Expose
    private String county;
    @SerializedName("postcode")
    @Expose
    private String postcode;
    @SerializedName("lat")
    @Expose
    private Double lat;
    @SerializedName("lng")
    @Expose
    private Double lng;
    @SerializedName("distance")
    @Expose
    private Double distance;
    @SerializedName("logo_url")
    @Expose
    private String logoUrl;

    List<Cinema> cinemas;

    public List<Cinema> getCinemas() {
        return cinemas;
    }

    public Integer getCinemaId() {
        return cinemaId;
    }

    public void setCinemaId(Integer cinemaId) {
        this.cinemaId = cinemaId;
    }

    public String getCinemaName() {
        return cinemaName;
    }

    public void setCinemaName(String cinemaName) {
        this.cinemaName = cinemaName;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getAddress2() {
        return address2;
    }

    public void setAddress2(String address2) {
        this.address2 = address2;
    }

    public String getCity() {
        return city;
    }

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

    public String getCounty() {
        return county;
    }

    public void setCounty(String county) {
        this.county = county;
    }

    public String getPostcode() {
        return postcode;
    }

    public void setPostcode(String postcode) {
        this.postcode = postcode;
    }

    public Double getLat() {
        return lat;
    }

    public void setLat(Double lat) {
        this.lat = lat;
    }

    public Double getLng() {
        return lng;
    }

    public void setLng(Double lng) {
        this.lng = lng;
    }

    public Double getDistance() {
        return distance;
    }

    public void setDistance(Double distance) {
        this.distance = distance;
    }

    public String getLogoUrl() {
        return logoUrl;
    }

    public void setLogoUrl(String logoUrl) {
        this.logoUrl = logoUrl;
    }
}

MovieGluApi(接口(interface))

public interface MovieGluApi {
    @GET("filmsNowShowing/")
    Call<Film> getFilmNames();

    @GET("cinemasNearby/")
    Call <Cinema> getNearbyCinema();
}

返回数据JSON

{
    "cinemas": [
        {
            "cinema_id": 9461,
            "cinema_name": "Broadway Cinema - Nottingham",
            "address": "14-18 Broad Street",
            "address2": "",
            "city": "Nottingham",
            "county": "Nottinghamshire",
            "postcode": "NG1 3AL",
            "lat": 52.954319,
            "lng": -1.14397,
            "distance": 45.481624870276,
            "logo_url": "https://assets.movieglu.com/chain_logos/uk/UK-0-sq.jpg"
        },
        {
            "cinema_id": 41088,
            "cinema_name": "Regent Street Cinema",
            "address": "307 Regent Street",
            "address2": "",
            "city": "London",
            "county": "Greater London",
            "postcode": "W1B 2HW",
            "lat": 51.51683,
            "lng": -0.14277,
            "distance": 100.14079068585,
            "logo_url": "https://assets.movieglu.com/chain_logos/uk/UK-0-sq.jpg"
        },
        {
            "cinema_id": 9438,
            "cinema_name": "Scott Cinemas - The Atrium Cinema",
            "address": "Atrium Building",
            "address2": "King Street",
            "city": "East Grinstead",
            "county": "West Sussex",
            "postcode": "RH19 3DJ",
            "lat": 51.1264,
            "lng": -0.00885,
            "distance": 123.65933949165,
            "logo_url": "https://assets.movieglu.com/chain_logos/uk/UK-1198-sq.jpg"
        },
        {
            "cinema_id": 9000,
            "cinema_name": "Scott Cinemas - Radway Cinema",
            "address": "Radway Place",
            "address2": "",
            "city": "Sidmouth",
            "county": "Devon",
            "postcode": "EX10 8TL",
            "lat": 50.682831,
            "lng": -3.23856,
            "distance": 136.92054971699,
            "logo_url": "https://assets.movieglu.com/chain_logos/uk/UK-1198-sq.jpg"
        },
        {
            "cinema_id": 10355,
            "cinema_name": "New Carlton Cinema",
            "address": "Market Street",
            "address2": "Market Hall",
            "city": "Okehampton",
            "county": "Devon",
            "postcode": "EX20 1HN",
            "lat": 50.739399,
            "lng": -4.00368,
            "distance": 150.44700252827,
            "logo_url": "https://assets.movieglu.com/chain_logos/uk/UK-1262-sq.jpg"
        }
    ],
    "status": {
        "count": 5,
        "state": "OK",
        "method": "cinemasNearby",
        "message": null,
        "request_method": "GET",
        "version": "****",
        "territory": "UK",
        "device_datetime_sent": "2020-05-17T08:30:17.360Z",
        "device_datetime_used": "2020-05-17 08:30:17"
    }
}

Answer 1

因为你忘记了:
@SerializedName("电影院")
@暴露
列出电影院；

希望对你有帮助。