Android 工作室：致命例外：DefaultDispatcher-worker-2

Question

Im 运行ning android 工作室 4.1.2 我正在尝试运行此交易：

QuestionDao.kt

  @Transaction
    suspend fun getRandomRN(num: Int):List<Question>{
     val result = getRandomWrongOrNotAnsweredQuestionsByCount(num)
        val last = getLastQuizNumber()

        val newResult = mutableListOf<Question>()

        result?.forEachIndexed{ index,element ->
            element.status=0
            element.quiz_number = last+1
            newResult[index] = element  // this is line 91
        }

        result?.let { updateQuestions(newResult) }
        return newResult
    }

运行宁应用抛出错误：

com.example.android.myapplication E/AndroidRuntime: FATAL EXCEPTION: DefaultDispatcher-worker-2
    Process: com.example.android.myapplication, PID: 25245
    java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
        at java.util.ArrayList.set(ArrayList.java:453)
        at com.example.android.webpooyeshelevatorquize.data.QuestionDao$DefaultImpls.getRandomRN(QuestionDao.kt:91)

QuestionDao.kt:91 是 newResult[index] = element.
顺便说一句，上下文是 Dispachers.IO

Answer 1

newResult 列表为空，您无法使用 newResult[index] = element 向其添加新元素。请改用 newResult += element 或 newResult.add(emenent)。

Answer 2

您实际上是在尝试访问数组的索引，而您还没有为它初始化任何元素。像这样初始化 newResult.add(i)

Android 工作室：致命例外：DefaultDispatcher-worker-2

Android studio: FATAL EXCEPTION: DefaultDispatcher-worker-2

android

kotlin

android-room

kotlin-coroutines