Question

如果类类型是泛型类型'T'，如何使用Gson进行解析？

具有泛型类的类，并且在其函数中将json字符串解析为泛型类型'T'在运行时的任何类型。但得到了

java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to com.example.model.content

这不适用于泛型'T'：

        val dataType = object : TypeToken<T>() {}.type
        val data = Gson().fromJson<T>(jsonStr, dataType)

调用此调用的方式是调用Content的'solid'类类型为Handler<Content>，其中通用的'T'（IHandler<T>}是预期的

FetchRemoteDataCommand("https", “testcontent.com", "v2/content”,
    params,
    Handler<Content>).execute()

这是类采用泛型类型：IHandler<T>，在运行时期望'T'应该是'solid'类型，即它应该是Content类型的调用

class FetchRemoteDataCommand<T>(scheme: String, authority: String, path: String,
                         params: HashMap<String, String>,
                         dataReadyCb: IHandler<T>) {


val mBaseUrl = "$scheme://$authority/"
val mPath = path
val mParams = params
var mDataReadyListener = dataReadyCb

override fun dispose() {……}

override fun execute() {
    getRemoteData(object : Observer<ResponseBody> {
        override fun onNext(responseBody: ResponseBody) {

            val dataType = object : TypeToken<T>() {}.type
            val jsonStr = responseBody.string()
            val data = Gson().fromJson<T>(jsonStr, dataType)  ***//<=== throws***

            ///
            mDataReadyListener(data)  //<== suppose to pass back the pared data back
            ……
        }
        …………
    })
}

private fun getRemoteData(observer: Observer<ResponseBody>) : Unit {

    val service: IRemoteRepositoryService = ServiceFactory.createRetrofitService(
                          IRemoteRepositoryService::class.java, mBaseUrl)

    service.getRemoteData(mPath, mParams) 
           .subscribe(observer)

    }
 }

Answer 1

从亨宁那里得到了一个想法（林雨成也有一个在运行时获得它的解决方案）get-generic-type-of-class-at-runtime 所以传入类类型而不是在运行时获取类型。

class FetchRemoteDataCommand<T>(scheme: String, authority: String, path: String,
                     params: HashMap<String, String>,
                     dataReadyCb: IHandler<T>, handlerClassType: Class<T>) {


val mBaseUrl = "$scheme://$authority/"
val mPath = path
val mParams = params
var mDataReadyListener = dataReadyCb
private val clazz: Class<T> = handlerClassType //findTypeArguments(this.javaClass)  <== some time return null???

private fun findTypeArguments(t: Type) : Class<T> {
    return if (t is ParameterizedType) {
        val typeArgs = t.actualTypeArguments
        typeArgs[0] as Class<T>
    } else {
        val c = t as Class<*>
        findTypeArguments(c.genericSuperclass)
    }
}

fun getClassType(): Class<T> {
    return clazz
}


override fun execute() {
    getRemoteData(object : Observer<ResponseBody> {
        override fun onNext(responseBody: ResponseBody) {

            //val dataType = object : TypeToken<T>() {}.type
            //val jsonStr = responseBody.string()
            //val data = Gson().fromJson<T>(jsonStr, dataType)  ***//<=== throws***

/// test generic type with the passed in class type instead of reflecting at runtime
            val responseRecieved = responseBody.string()
            val data = Gson().fromJson(responseRecieved, getClassType())

            ///
            mDataReadyListener(data)  //<== suppose to pass back the pared data back
        ……
    }
    …………
    })
}

kotlin，如何使用Gson解析泛型类型是一个用泛型类型定义的函数

1 个答案: