object - Kotlin .add覆盖MutableList中的所有列表项

Question

我有一个包含可变列表的对象

object TrackingEventsList {
    var EventDate: String = ""
    var EventDescription: String = ""
}

object Waybill {
    var WaybillNumber: String = ""
    var OriginHub: String = ""
    var TrackingEvents: MutableList<TrackingEventsList> = ArrayList()
}

当我尝试添加Waybill.TrackingEvents时，所有以前的实例都将被覆盖并复制最后添加的TrackingEvent。

private fun fillTracking(events: NodeList) {
    var list = TrackingEventsList
    for (x: Int in 0 until events.length) {
        var tName = (events.item(x) as Element).tagName
        var event = (events.item(x).firstChild as Text).wholeText
        if (tName == "EventDate") {
            list.EventDate = event
        }
        if (tName == "EventDescription") {
            list.EventDescription = event
        }
    }
    Waybill.TrackingEvents.plus(list)
}

调用fillTracking 3次后的结果:

Waybill.TrackingEvents[0].EventDescription = "Event3"
Waybill.TrackingEvents[1].EventDescription = "Event3"
Waybill.TrackingEvents[2].EventDescription = "Event3"

Answer 1

由于TrackingEventsList是一个对象，因此它意味着它是一个单例(或只有一个实例)。当您遍历循环时，始终会更新TrackingEventsList对象的同一实例。

将TrackingEventsList更改为:

data class TrackingEventsList(var eventDate: String, var eventDescription: String)

每次循环时都创建一个新实例，然后将其添加到列表的末尾:

private fun fillTracking(events: NodeList) {
    var eventDate: String = ""
    var eventDescription: String = ""
    for (x: Int in 0 until events.length) {
        val tName = (events.item(x) as Element).tagName
        val event = (events.item(x).firstChild as Text).wholeText
        if (tName == "EventDate") {
            eventDate = event
        }
        if (tName == "EventDescription") {
            eventDescription = event
        }
    }
    Waybill.TrackingEvents.plus(TrackingEventsList(eventDate, eventDescription))
}