改造自定義回調通用類型

Question

我正在擴展默認的 Retrofit 2 回調：

abstract class APICallback<T> implements Callback<T> {

    @Override
    public void onResponse(Call<T> call, Response<T> response) {
        if (!response.isSuccessful()) {
            // Cast response.body() to my POJO class, results in null
            MyClass myClass = (MyClass) response.body();
        }
    }

    @Override
    public void onFailure(Call<T> call, Throwable t) {
        // TODO ...
    }
}

如何將 Response 的通用類型向下轉換為我自己的類？ 這個過程應該是自動的嗎？ 我正在為客戶端使用 GsonConverter。

Answer 1

我認為您必須修改 AdapterFactory 然后注冊改造

public class APICallAdapterFactory extends CallAdapter.Factory {

@Nullable
@Override
public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
    final Type responseType = ((ParameterizedType) returnType).getActualTypeArguments()[0];
    return new CallAdapter<Object, Object>() {
        @Override
        public Type responseType() {
            return responseType;
        }

        @Override
        public Object adapt(Call<Object> call) {
            return new APICallAdapter<>(call);
        }
    };
}

和

 private static Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(APIService.baseUrl)
        .client(client)
        .addConverterFactory(GsonConverterFactory.create())
        .addCallAdapterFactory(new APICallAdapterFactory())
        .build();

Answer 2

用 MyClass 替換 T

class APICallback implements Callback<MyClass> {

    @Override
    public void onResponse(Call<MyClass> call, Response<MyClass> response) {
        if (response.isSuccessful()) {
            // Cast response.body() to my POJO class, results in null
             MyClass myClass = response.body();
        }
    }

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

    }
}

Answer 3

你可以通過這個處理

Gson gson = new Gson();
MyClass myClass = gson.fromJson(response.body(), MyClass.class);