I have this class

data class CameraList(var cameraName: String, var id: Int, var density:
ArrayList<Size>) : Serializable

and i try to save to shared preference

fun saveDataObject(context: Context, variable: String, cameraList:
ArrayList<CameraList>) {

val sharedPreferences =
PreferenceManager.getDefaultSharedPreferences(context)
val gson = Gson()
try {
sharedPreferences.edit()
.putString(variable, gson.toJson(cameraList)
.apply()
} catch ( e: OutOfMemoryError ) {
}
}

fun getDataObject(context: Context, variable: String):
ArrayList<CameraList>? {
val sharedPreferences =
PreferenceManager.getDefaultSharedPreferences(context)
val userList: ArrayList<CameraList> = ArrayList()
val data: String? = sharedPreferences.getString(variable,
userList.toString())
val gson = Gson()
return gson.fromJson(data, object :
TypeToken<ArrayList<CameraList>>() {}.type)
}

and i got this error

Caused by: com.google.gson.JsonSyntaxException:
java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at
line 1 column 2 path $

how to convert ArrayList<Size> from data class CameraList(var
cameraName: String, var id: Int, var density: ArrayList<Size>)