将java类文件转换为kotlin导致编译错误

Question

 public class CallbackWrapper<T> implements Callback<T> {
   private Wrapper<T> wrapper;

   public CallbackWrapper(Wrapper<T> wrapper) {
      this.wrapper = wrapper;
   }

   public void onFailure(Call<T> call, Throwable t) {
      wrapper.onResult(t, null);
   }

   public void onResponse(Call<T> call, Response<T> response) {
      wrapper.onResult(null, response);
   }

   public interface Wrapper<T> {
      void onResult(@Nullable Throwable t, @Nullable Response<T> response);
   }
}

request.enqueue(CallbackWrapper<RegisterResponse> { throwable, response ->
     response?.let { callBack.onResponse(response.body() ?: RegisterResponse()) }
     throwable?.let { callBack.onFailed(throwable.message!!) }
 })

class CallbackWrapper<T>(private val wrapper: CallbackWrapper.Wrapper<T>) : Callback<T> {

    override fun onFailure(call: Call<T>, t: Throwable) {
        wrapper.onResult(t, null)
    }

    override fun onResponse(call: Call<T>, response: Response<T>) {
        wrapper.onResult(null, response)
    }

    interface Wrapper<T> {
        fun onResult(t: Throwable?, response: Response<T>?)
    }
}

问题是，在将它转换为Kotlin之后，我使用这个类的代码块不起作用了。我不明白他们之间有什么区别。

下面是编译错误日志

Error:(17, 63) Type mismatch: inferred type is (???, ???) -> [ERROR :<ERROR FUNCTION RETURN TYPE>] but CallbackWrapper.Wrapper<RegisterResponse> was expected
Error:(17, 65) Cannot infer a type for this parameter. Please specify it explicitly.
Error:(17, 76) Cannot infer a type for this parameter. Please specify it explicitly.

Answer 1

据我所知，您的代码有两个问题。

首先，Kotlin不允许使用lambda实现Kotlin函数接口，因此lambda不能工作（它允许实现Java函数接口，因为Java没有适当的函数类型）。因此，要调用代码不变，您需要使用对象表示法：

request.enqueue(CallbackWrapper<RegisterResponse>(object : CallbackWrapper.Wrapper<RegisterResponse> {
        override fun onResult(throwable: Throwable?, response: Response<RegisterResponse>?) {
            response?.let { callBack.onResponse(response.body() ?: RegisterResponse()) }
            throwable?.let { callBack.onFailure(throwable.message!!) }
        }
    }))

如果您喜欢使用lambdas，可以以不同的方式声明callbackwrapper类：

typealias Wrapper<T> = (t: Throwable?, response: Response<T>?) -> Unit
class OtherCallbackWrapper<T>(val wrapper: Wrapper<T>) : Callback<T> {
    override fun onFailure(call: Call<T>, t: Throwable) = wrapper.invoke(t, null)
    override fun onResponse(call: Call<T>, response: Response<T>) = wrapper.invoke(null, response)
}