无法使reverfit2接口适用于所有型号

Question

我在我的应用程序中使用了reverfit2，它工作得真的很好，但是我试图通过传递一个动态模型，为所有类型的GET方法请求使用一个单一的接口。当我尝试使用下面的代码时，它在运行时给出错误

public interface LoadDataServiceTest<T> {
        @GET
        Call<T> getModel(@Url String url, @QueryMap Map<String, String> options);
    }

public class ModelTest<T> {
    @SerializedName("status")
    private String status;
    @SerializedName("message")
    private String message;
    @SerializedName("users")
    private T data;

    public String getStatus() {
        return status;
    }

    public String getMessage() {
        return message;
    }

    public T getData() {
        return data;
    }
}

LoadDataServiceTest<ModelTest<JsonArray>> service = retrofit.create((Class<LoadDataServiceTest<ModelTest<JsonArray>>>) (Class<?>) APIs.LoadDataServiceTest.class);
        Map<String, String> parameters = new HashMap<>();
        parameters.put("user_id",userId);
        Call<ModelTest<JsonArray>> call = service.getModel(APIs.GET_USERS, parameters);

错误：

致命异常：主进程：com.iu.colgatePalmolive,pid：16808 java.lang.runtimeException：无法启动activity ComponentInfo{com.iu.colgatePalmolive/com.iu.hfl_ccp.loginActivity}：java.lang.IllegalArgumentException：方法返回类型不能包含类型变量或通配符：Retrofit2.调用Android.app.ActivityThread.PerformLaunchActivity(ActivityThread.java:2666)在Android.app.ActivityThread.HandleLaunchActivityava.lang.IllegalArgumentException：方法返回类型不能包含类型变量或通配符：Retrofit2.ServiceMethod$Builder.MethodError(ServiceMethod.java:720)在Retrofit2.ServiceMethod$Builder.MethodError(ServiceMethod.java:711)在Retrofit2.ServiceMethod$Builder.CreateCallAdapter(ServiceMethod.java:224)在Retrofit2.ServiceMethod.java:160)在Retrofit2.Retrofit.LoadServiceMethod

Answer 1

我使用以下方法。首先，我实现了自定义调用

public class ProxyConvertCall<Tin,Tout> implements Call<Tout> {
    Converter<Tin,Tout> converter;
    Call<Tin> innerCall;

    public ProxyConvertCall(Call<Tin> jcall, Converter<Tin,Tout> converter){
        this.innerCall = jcall;
        this.converter = converter;
        }

    @Override
    public Response<Tout> execute() throws IOException {
        Response<Tin> response = innerCall.execute();
        if (response.isSuccessful()){
            return Response.success(converter.Convert(response.body()),response.raw());
        }
        else return Response.error(response.code(), response.errorBody());
    }

    @Override
    public void enqueue(final Callback<Tout> callback) {
        final Call<Tout> self = this;
        this.innerCall.enqueue(new Callback<Tin>() {  
            @Override
            public void onResponse(Call<Tin> call, Response<Tin> response) {
                if (response.isSuccessful()){
                    callback.onResponse(self, Response.success(converter.Convert(response.body()), response.raw()));
                }
                else callback.onResponse(self, Response.error(response.code(), response.errorBody()));
            }
            @Override
            public void onFailure(Call<Tin> call, Throwable t) {
                callback.onFailure(self,t);
            }
        });

    }

    @Override
    public boolean isExecuted() {
        return innerCall.isExecuted();
    }

    @Override
    public void cancel() {
        innerCall.cancel();

    }

    @Override
    public boolean isCanceled() {
        return innerCall.isCanceled();
    }

    @Override
    public Call<Tout> clone() {
        return new ProxyConvertCall<>(innerCall,converter);
    }

    @Override
    public Request request() {
        return innerCall.request();
    }
}

它使用转换器将调用 调整为调用 。

@FunctionalInterface 
public interface Converter<Tin, Tout> {
    public Tout Convert(Tin in);
}

对于您的服务，您必须创建服务接口，该接口为单个对象返回JsonObject，为数组返回JsonArray

  public interface LoadDataServiceTest {
     @GET
     public Call<JsonObject> getModelTest(@Url String url, @QueryMap Map<String, String> options);

     @GET
     public Call<JsonObject> getModel(@Url String url, @QueryMap Map<String, String> options);

     @GET
     public Call<JsonArray> getModels(@Url String url, @QueryMap Map<String, String> options);


}

   public class LoadDataServiceTestGeneric<T> {
     Converter<JsonObject,ModelTest<T>> fromJsonObjectToModelTest;
     Converter<JsonObject,T> fromJsonObject;
     Converter<JsonArray,List<T>> fromJsonArray;
     LoadDataServiceTest service;

    public LoadDataServiceTestGeneric(Class<T> classOfT, LoadDataServiceTest service){  
        this.service = service;
        Gson gson  = new GsonBuilder().create();
        GenericListType<T> genericListTypeOfT = new GenericListType<T>(classOfT);
        fromJsonObject = (t)->gson.fromJson(t,classOfT);
        fromJsonArray =(t)->gson.fromJson(t,genericListTypeOfT);
    }
    public Call<ModelTest<T>> getModelTest(String url, Map<String, String> options){ 
        return new ProxyConvertCall<>(service.getModelTest(url, options), fromJsonObjectToModelTest);
    }

    public Call<T> getModel(String url, Map<String, String> options){ 
        return new ProxyConvertCall<>(service.getModel(url, options), fromJsonObject);
    }

    Call<List<T>> getModels(String url, Map<String, String> options){ 
        return new ProxyConvertCall<>(service.getModels(url, options), fromJsonArray);
    }

}

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.List;

public class GenericListType<T> implements ParameterizedType {

    private Type wrapped;

    public GenericListType(Type wrapped) {
        this.wrapped = wrapped;
    }

    public Type[] getActualTypeArguments() {
        return new Type[] {wrapped};
    }

    public Type getRawType() {
        return  List.class;
    }

    public Type getOwnerType() {
        return null;
    }

}

ModelTestType是ParameterizedType。用于将类型参数传递给modeltesttype 的gson

public class ModelTestType  implements ParameterizedType {

        private Type wrapped;

        public ModelTestType(Type wrapped) {
            this.wrapped = wrapped;
        }

        public Type[] getActualTypeArguments() {
            return new Type[] {wrapped};
        }

        public Type getRawType() {
            return  ModelTest.class;
        }

        public Type getOwnerType() {
            return null;
        }

    }

然后可以使用所需的类型实例化LoadDataServiceTestGeneric。