Get Array of object From Firestore

问题

I getting data from firestore put it in to ArrayList

arraylist=document.get("questionsList") as ArrayList<Question>
Toast.makeText(context, arraylist.size, Toast.LENGTH_LONG).show()

and its ok when I print the size of Array put when I need to get Question Item from Arraylist

Toast.makeText(context, arraylist!![0].question, Toast.LENGTH_LONG).show()

the result is java.util.HashMap cannot be cast to Question

document in firestore image here

Question class

class Question (var question:String,var choices:ArrayList<String>,var correctAnswer:String
                ,private var userAnswer:String): Parcelable {
    constructor(parcel: Parcel) : this(
        parcel.readString()!!, arrayListOf<String>().apply {
            parcel.readString()
        },
        parcel.readString()!!,
        parcel.readString()!!
    )
    constructor():this(question="",choices = ArrayList<String>(),correctAnswer = "",userAnswer = "")

    override fun writeToParcel(parcel: Parcel, flags: Int) {
        parcel.writeString(question)
        parcel.writeString(correctAnswer)
        parcel.writeString(userAnswer)
    }

    override fun describeContents(): Int {
        return 0
    }

    companion object CREATOR : Parcelable.Creator<Question> {
        override fun createFromParcel(parcel: Parcel): Question {
            return Question(parcel)
        }

        override fun newArray(size: Int): Array<Question?> {
            return arrayOfNulls(size)
        }
    }
}

回答1:

You can use document.toObject to cast your Firestore result to a Kotlin class. If you just use get on the field you will get a HashMap. In your case you could create a class that has a questionsList property and then cast it to your class. I haven't used Kotlin in a few months, but I believe it would be something like this:

data class MyQuestionList(
    var questionsList: ArrayList<Question>
)

val myQuestionList = document.toObject(MyQuestionList::class.java)

Toast.makeText(context, myQuestionList.questionsList!![0].question, Toast.LENGTH_LONG).show()

Also, be careful with !! as it will cause a runtime exception if the object is null.

来源：https://stackoverflow.com/questions/54647028/get-array-of-object-from-firestore

标签

android

firebase

dictionary

arraylist

kotlin