android - 在闭包中捕获时，包装到要修改的参考对象中

Question

所以我对 android 上的 Kotlin 有点陌生，对“ CLOSURES ”是什么感到非常困惑。我也看过很多视频，但什么也没有。

我在第 5 行完成了对相互列表的初始化，但是我无法在try/catch块中为其设置值。

谁能帮帮我吗。

private fun returnArray(url: String) : MutableList<String> {

    Log.d("Alele", "returnArray(url)")

    var arrayList = mutableListOf<String>()

    val jsonObjectRequest = JsonObjectRequest(
            Request.Method.GET,
            url,
            null,
            Response.Listener { response ->
                try {

                    Log.d("Alele", "Try block")
                    var jsonObject = response.getJSONObject("response").getJSONArray("docs").getJSONObject(0)

                    Log.d("Alele", jsonObject.toString())

                    var id = jsonObject.getString("id")
                    Log.d("Alele", id.toString())

                    var journal = jsonObject.getString("journal")
                    Log.d("Alele", journal)

                    arrayList[0] = id
                    arrayList[1] = journal

                } catch (e: JSONException) {
                    Log.d("Alele", "catch block")
                    e.printStackTrace()
                }
            },
            Response.ErrorListener {
                it.printStackTrace()
                Log.d("Alele", it.printStackTrace().toString())
            })
    Log.d("Alele", " $arrayList[0]")
    Log.d("Alele", " $arrayList[1]")

    // add the queue to the request
    requestQueue.add(jsonObjectRequest)
    return arrayList
}

这是产生的日志。一切都按预期打印出来，但是，行

                    arrayList[0] = id
                    arrayList[1] = journal

导致应用程序崩溃，每当我将光标放在这些行上以获取任何提示时，我都会被包装到要修改的参考对象中，当在闭包中捕获时，这让我很难理解。

2020-02-21 10:22:48.560 31603-31603/com.hylton.volleyproject D/Alele: returnArray(url)

2020-02-21 10:22:48.563 31603-31603/com.hylton.volleyproject D/Alele:  [][0]

2020-02-21 10:22:48.563 31603-31603/com.hylton.volleyproject D/Alele:  [][1]

2020-02-21 10:22:51.108 31603-31603/com.hylton.volleyproject D/Alele: Try block

2020-02-21 10:22:51.110 31603-31603/com.hylton.volleyproject D/Alele: {"id":"10.1371\/journal.pone.0084896","journal":"PLoS ONE","eissn":"1932-6203","publication_date":"2014-01-17T00:00:00Z","article_type":"Research Article","author_display":["Marcel A. L. M. van Assen","Robbie C. M. van Aert","Michèle B. Nuijten","Jelte M. Wicherts"],"abstract":["Background: De Winter and Happee [1] examined whether science based on selective publishing of significant results may be effective in accurate estimation of population effects, and whether this is even more effective than a science in which all results are published (i.e., a science without publication bias). Based on their simulation study they concluded that “selective publishing yields a more accurate meta-analytic estimation of the true effect than publishing everything, (and that) publishing nonreplicable results while placing null results in the file drawer can be beneficial for the scientific collective” (p.4). Methods and Findings: Using their scenario with a small to medium population effect size, we show that publishing everything is more effective for the scientific collective than selective publishing of significant results. Additionally, we examined a scenario with a null effect, which provides a more dramatic illustration of the superiority of publishing everything over selective publishing. Conclusion: Publishing everything is more effective than only reporting significant outcomes. "],"title_display":"Why Publishing Everything Is More Effective than Selective Publishing of Statistically Significant Results","score":9.342657}

2020-02-21 10:22:51.110 31603-31603/com.hylton.volleyproject D/Alele: 10.1371/journal.pone.0084896

2020-02-21 10:22:51.110 31603-31603/com.hylton.volleyproject D/Alele: PLoS ONE

这是崩溃报告打印出来的

E/AndroidRuntime: FATAL EXCEPTION: main

    Process: com.hylton.volleyproject, PID: 569

    java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

        at java.util.ArrayList.set(ArrayList.java:453)

        at com.hylton.volleyproject.MainActivity$returnArray$jsonObjectRequest$1.onResponse(MainActivity.kt:71)

        at com.hylton.volleyproject.MainActivity$returnArray$jsonObjectRequest$1.onResponse(MainActivity.kt:26)

        at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:90)

        at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:102)

        at android.os.Handler.handleCallback(Handler.java:883)

        at android.os.Handler.dispatchMessage(Handler.java:100)

        at android.os.Looper.loop(Looper.java:214)

        at android.app.ActivityThread.main(ActivityThread.java:7356)

        at java.lang.reflect.Method.invoke(Native Method)

        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)

        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

I/Process: Sending signal. PID: 569 SIG: 9

Application terminated.

标签： androidkotlinclosuresandroid-volley