在我的例子中：

public class MyInterceptor implements Interceptor {

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        request = addHeaderFields(request);
        request = modifyRequestBody(request);
        return chain.proceed(request);
    }

    /**
     * add new Headers
     */
    private Request addHeaderFields(Request request) {
        return request.newBuilder()
                .addHeader("timestamp", String.valueOf(new Date().getTime()))
                .addHeader("os", "android")
                .build();
    }

    /**
     * add new post fields
     */
    private Request modifyRequestBody(Request request) {
        if ("POST".equals(request.method())) {
            if (request.body() instanceof FormBody) {
                FormBody.Builder bodyBuilder = new FormBody.Builder();
                FormBody formBody = (FormBody) request.body();
                // Copy the original parameters first
                for (int i = 0; i < formBody.size(); i++) {
                    bodyBuilder.addEncoded(formBody.encodedName(i), formBody.encodedValue(i));
                }
                // Add common parameters
                formBody = bodyBuilder
                        .addEncoded("userid", "001")
                        .addEncoded("param2", "value2")
                        .build();
                request = request.newBuilder().post(formBody).build();
            }
        }
        return request;
    }
}

拦截器的头部和身体修改：

class OkHttpInterceptor() : Interceptor {

    override fun intercept(chain: Interceptor.Chain): Response {
        val request = chain.request()
        val requestWithAndroidHeaders = addHeaderFields(request)
        val response = chain.proceed(requestWithAndroidHeaders)
        return modifyResponseBody(response)
    }

    private fun addHeaderFields(request: Request): Request = request.newBuilder()
                .addHeader("Content-Type", "application/json")
                .addHeader("User-Agent", "Android")
                .addHeader("TraceId", "abc 123")
                .build()

    private fun modifyResponseBody(response: Response): Response {
        val responseString = response.body()?.charStream()?.readText()
        val responseJson = responseString?.let { stringToJson(it) }
        return if (responseJson != null) {
            val contentType: MediaType? = response.body()?.contentType()
            val responseBody = ResponseBody.create(contentType, responseJson.toString())
            response.newBuilder().body(responseBody).build()
        } else {
           response
        }
    }

    private fun stringToJson(responseString: String): JSONObject? = try {
        JSONObject(responseString).put("traceId", "abc 123")
    } catch (e: JSONException) {
        println(e.message)
        null
    }
}

确定Http客户端：

val okHttpInterceptor = OkHttpInterceptor()
val client = OkHttpClient.Builder()
client.interceptors().add(okHttpInterceptor)
client.build()

也许您还想添加日志记录：

val logging = HttpLoggingInterceptor()
if(BuildConfig.DEBUG) {
    logging.level = HttpLoggingInterceptor.Level.BODY
} else {
    logging.level = HttpLoggingInterceptor.Level.NONE
}
val okHttpInterceptor = OkHttpInterceptor()
val client = OkHttpClient.Builder()
client.interceptors().add(okHttpInterceptor)
client.interceptors().add(logging)
client.build()

这应该工作，虽然我做了java，认为它你应该在Kotlin工作出来

public Response intercept(@NonNull Chain chain) throws IOException {
             Request original = chain.request();
             // Request customization: add request headers
             Request.Builder requestBuilder = original.newBuilder();
             //requestBuilder.addHeader("key",API_KEY);
             requestBuilder.addHeader("Content-Type","application/json");

             Request request = requestBuilder.build();
             return chain.proceed(request);
         }