Android JSON（POJO）模型响应

我的JSON的响应模型有问题

我正在使用hitbtc API:

将此文件转换为POJO模型时，我只有此文件：

public class Currency {

@SerializedName("id")
@Expose
private String id;
@SerializedName("fullName")
@Expose
private String fullName;
@SerializedName("crypto")
@Expose
private Boolean crypto;
@SerializedName("payinEnabled")
@Expose
private Boolean payinEnabled;
@SerializedName("payinPaymentId")
@Expose
private Boolean payinPaymentId;
@SerializedName("payinConfirmations")
@Expose
private Integer payinConfirmations;
@SerializedName("payoutEnabled")
@Expose
private Boolean payoutEnabled;
@SerializedName("payoutIsPaymentId")
@Expose
private Boolean payoutIsPaymentId;
@SerializedName("transferEnabled")
@Expose
private Boolean transferEnabled;
@SerializedName("delisted")
@Expose
private Boolean delisted;
@SerializedName("payoutFee")
@Expose
private String payoutFee;

public String getId() {
    return id;
}

public void setId(String id) {
    this.id = id;
}

public String getFullName() {
    return fullName;
}

public void setFullName(String fullName) {
    this.fullName = fullName;
}

public Boolean getCrypto() {
    return crypto;
}

public void setCrypto(Boolean crypto) {
    this.crypto = crypto;
}

public Boolean getPayinEnabled() {
    return payinEnabled;
}

public void setPayinEnabled(Boolean payinEnabled) {
    this.payinEnabled = payinEnabled;
}

public Boolean getPayinPaymentId() {
    return payinPaymentId;
}

public void setPayinPaymentId(Boolean payinPaymentId) {
    this.payinPaymentId = payinPaymentId;
}

public Integer getPayinConfirmations() {
    return payinConfirmations;
}

public void setPayinConfirmations(Integer payinConfirmations) {
    this.payinConfirmations = payinConfirmations;
}

public Boolean getPayoutEnabled() {
    return payoutEnabled;
}

public void setPayoutEnabled(Boolean payoutEnabled) {
    this.payoutEnabled = payoutEnabled;
}

public Boolean getPayoutIsPaymentId() {
    return payoutIsPaymentId;
}

public void setPayoutIsPaymentId(Boolean payoutIsPaymentId) {
    this.payoutIsPaymentId = payoutIsPaymentId;
}

public Boolean getTransferEnabled() {
    return transferEnabled;
}

public void setTransferEnabled(Boolean transferEnabled) {
    this.transferEnabled = transferEnabled;
}

public Boolean getDelisted() {
    return delisted;
}

public void setDelisted(Boolean delisted) {
    this.delisted = delisted;
}

public String getPayoutFee() {
    return payoutFee;
}

public void setPayoutFee(String payoutFee) {
    this.payoutFee = payoutFee;
}

}

在下一步中，我想获得项目列表，如下所示：

 public class CurrencyResponse {
@SerializedName("page")
private int page;
@SerializedName("results")
private List<Currency> 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 List<Currency> getResults() {
    return results;
}

public void setResults(List<Currency> 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;
}
}

MainActivity.java：

   public class MainActivity extends AppCompatActivity {

   private static final String TAG = MainActivity.class.getSimpleName();


// TODO - insert your themoviedb.org API KEY here
private final static String API_KEY = "My_key";


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

    if (API_KEY.isEmpty()) {
        Toast.makeText(getApplicationContext(), "Please obtain your API KEY from hitbtc.com first!", Toast.LENGTH_LONG).show();
        return;
    }

    final RecyclerView recyclerView = (RecyclerView) findViewById(R.id.movies_recycler_view);
    LinearLayoutManager manager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(manager);
    recyclerView.setHasFixedSize(true);



    ApiInterface apiService =
            ApiClient.getClient().create(ApiInterface.class);

    Call<CurrencyResponse> call = apiService.getCurrencies(API_KEY);
    call.enqueue(new Callback<CurrencyResponse>() {
        @EverythingIsNonNull
        public void onResponse(Call<CurrencyResponse> call, Response<CurrencyResponse> response) {
            int statusCode = response.code();
            List<Currency> currencies = response.body().getResults();
            recyclerView.setAdapter(new CurrenciesAdapter(currencies, R.layout.list_item_currency, getApplicationContext()));
        }

        @Override
        public void onFailure(Call<CurrencyResponse> call, Throwable t) {
            // Log error here since request failed
            Log.e(TAG, t.toString());
        }
    });
}
}

---

我查看了您在描述中提供的上述链接，我知道有一个数组作为响应。因此，根据这一点，您不应该需要

CurrencyResponse

类。只要

Currency

class就足够了

在改型界面中，api方法应返回

货币列表

。e、 g.

List getCurrencyList（）

。它应该会起作用

---

对于NPE，可能的原因应该是您试图从api响应中不包含的这些类访问字段，因此该字段将为null，访问该字段将抛出NPE。您可以检查stacktrace以了解哪个字段访问正在抛出NPE，或者您可以共享

stacktrace

，以便该社区可以帮助您。

我检查了您在说明中提供的上述链接，我知道有一个数组响应。因此，根据这一点，您不应该需要

CurrencyResponse

类。只要

Currency

class就足够了

在改型界面中，api方法应返回

货币列表

。e、 g.

List getCurrencyList（）

。它应该会起作用

---

对于NPE，可能的原因应该是您试图从api响应中不包含的这些类访问字段，因此该字段将为null，访问该字段将抛出NPE。您可以检查stacktrace以了解哪个字段访问正在抛出NPE，或者您可以共享

stacktrace

，以便该社区可以帮助您。

您在哪里拥有NPE？在哪一行？您是否会共享堆栈跟踪（来自异常）？显示适配器代码，并根据API响应（来自给定链接）发布堆栈跟踪信息，无需

CurrencyResponse

类。只需在API界面中使用

List

。@Basi，在您有NPE的地方，列表就完成了？在哪一行？您是否会共享堆栈跟踪（来自异常）？显示适配器代码，并根据API响应（来自给定链接）发布堆栈跟踪信息，无需

CurrencyResponse

类。只需在API界面中使用

List

。@Basi，列表已完成

   public class MainActivity extends AppCompatActivity {

   private static final String TAG = MainActivity.class.getSimpleName();


// TODO - insert your themoviedb.org API KEY here
private final static String API_KEY = "My_key";


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

    if (API_KEY.isEmpty()) {
        Toast.makeText(getApplicationContext(), "Please obtain your API KEY from hitbtc.com first!", Toast.LENGTH_LONG).show();
        return;
    }

    final RecyclerView recyclerView = (RecyclerView) findViewById(R.id.movies_recycler_view);
    LinearLayoutManager manager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(manager);
    recyclerView.setHasFixedSize(true);



    ApiInterface apiService =
            ApiClient.getClient().create(ApiInterface.class);

    Call<CurrencyResponse> call = apiService.getCurrencies(API_KEY);
    call.enqueue(new Callback<CurrencyResponse>() {
        @EverythingIsNonNull
        public void onResponse(Call<CurrencyResponse> call, Response<CurrencyResponse> response) {
            int statusCode = response.code();
            List<Currency> currencies = response.body().getResults();
            recyclerView.setAdapter(new CurrenciesAdapter(currencies, R.layout.list_item_currency, getApplicationContext()));
        }

        @Override
        public void onFailure(Call<CurrencyResponse> call, Throwable t) {
            // Log error here since request failed
            Log.e(TAG, t.toString());
        }
    });
}
}

  --------- beginning of crash
  2019-03-11 13:58:12.020 3325-3325/com.example.mojpierwszyrest 
  E/AndroidRuntime: FATAL EXCEPTION: main
  Process: com.example.mojpierwszyrest, PID: 3325
  java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List com.example.mojpierwszyrest.model.CurrencyResponse.getResults()' on a null object reference
    at com.example.mojpierwszyrest.acitivity.MainActivity$1.onResponse(MainActivity.java:63)
    at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:71)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run
    (RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
    2019-03-11 13:58:12.563 3325-3325/com.example.mojpierwszyrest I/Process: 
    Sending signal. PID: 3325 SIG: 9