java.lang.IndexOutOfBoundsException: 索引: 0,大小: 0 Kotlin 中的错误

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英文:

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 Error in Kotlin

问题

尝试从数组列表中获取货币值,我期望通过get()函数来调用它。但是我得到了IndexOutOfBounds错误。

英文:

I am trying to build an currency exhanger app using an API.
When I try to get the first currency, i get indexOutOfBounds Exception. I know that exchangeDetails Array empty is and i cannot reach to an empty array. But i dont know how to fix it.

This is CalculateView

Column {
                    if(calculateViewModel.loading){
                        CircularProgressIndicator()
                    }else{
                        Text(text = calculateViewModel.exchangeDetail[0].get("EUR").toString())
                        Text(text = calculateViewModel.exchangeDetail[0].get(currency2).toString())
                    }

                }

and this is CalculateViewModel

class CalculateViewModel: ViewModel() {

    private val exchangeService = ExchangeService()
    var loading: Boolean by mutableStateOf(false)
    var errorMessage : String by mutableStateOf("")
    var exchangeDetail : MutableList<Map<String, Float>> by mutableStateOf(mutableListOf())

    fun getExchangeRatio(input1: String, input2: String) = viewModelScope.launch {
        errorMessage = ""
        loading = true
        try {
            val ratio = exchangeService.getExchangeCourse(input1,input2)
            exchangeDetail.add(ratio.data)
        }catch (e: Exception){
            errorMessage = e.message.toString()
        }finally {
            loading = false
        }
    }

}

exhchangeDto class

@kotlinx.serialization.Serializable
data class ExchangeDto (

    val data: Map<String, Float>

    //Zugriff über .get()
)

APIManager


class APIManager {
    private val apiKey = "Om1xoJkPAxk9neFbFvzezQtxAuNHdSERTfN8CPbk"
    var jsonHttpClient = HttpClient {
        expectSuccess = true
        install(ContentNegotiation) {
            json(Json {
                ignoreUnknownKeys = true
            })
        }
        defaultRequest {
            url.host = "api.freecurrencyapi.com"
            url.protocol = URLProtocol.HTTPS
            url.encodedPath = "/v1/latest?apikey=$apiKey" + url.encodedPath
            contentType(ContentType.Application.Json)
            headers {
                append(HttpHeaders.Authorization,
                    "Bearer $apiKey")
            }

        }

        HttpResponseValidator {
            getCustomResponseValidator(this)
        }

    }
}

Thanks...

I tried to get the currency value from an array list, i was expecting to call it via get() function. I got IndexOutOfBounds error.

答案1

得分: 0

有几种方法可以避免这里的错误。

其中一种方法是使用 firstOrNull 方法,而不是使用 [0] 进行访问。

示例

if (calculateViewModel.loading) {
    CircularProgressIndicator()
} else {
    Text(text = calculateViewModel.exchangeDetail.firstOrNull()?.get("EUR")?.toString() ?: "")
    Text(text = calculateViewModel.exchangeDetail.firstOrNull()?.get(currency2)?.toString() ?: "")
}

请注意,使用这种 "修复" 方法时,您需要有一个默认值(在这里是空字符串)。您可以根据需要将其更改为其他值。

另一种方法是在尝试打印这些文本之前检查数组是否为空。

示例

if (calculateViewModel.loading) {
    CircularProgressIndicator()
} else {
    if (calculateViewModel.exchangeDetail.isNotEmpty()) {
        Text(text = calculateViewModel.exchangeDetail[0].get("EUR").toString())
        Text(text = calculateViewModel.exchangeDetail[0].get(currency2).toString())
    } else {
        // 打印您想要的内容...
    }
}
英文:

There is several ways to avoid error here.

One way could be to use the firstOrNull method instead of accessing it using [0]

Example

if(calculateViewModel.loading){
                        CircularProgressIndicator()
                    }else{
                        Text(text = calculateViewModel.exchangeDetail.firstOrNull()?.get("EUR")?.toString() ?: "")
                        Text(text = calculateViewModel.exchangeDetail.firstOrNull()?.get(currency2)?.toString() ?: "")
                    }

Note that with this " fix " you need to have a default value (empty string here). You can change it for whatever you like.

One other way could be to check if the array is empty or not before trying to print those texts.

Example


if(calculateViewModel.loading){
        CircularProgressIndicator()
    }else{
        if(calculateViewModel.exchangeDetail.isNotEmpty()) {
            Text(text = calculateViewModel.exchangeDetail[0].get("EUR").toString())
            Text(text = calculateViewModel.exchangeDetail[0].get(currency2).toString())
        } else {
            // print whatever you want ...
        }
    }

huangapple
  • 本文由 发表于 2023年3月9日 16:56:03
  • 转载请务必保留本文链接:https://go.coder-hub.com/75682324.html
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