Unfortunately, JsonArray does not expose an iterator. So you will have to iterate through it using an index range:

for (i in 0 until persons.length()) {
    val item = persons.getJSONObject(i)

    // Your code here
}

You need to first get a hold of the array nested in your object with the "items" key, and then you can iterate over that array. The basic way to do this (if you're sure that it only contains strings) would be to loop over its indexes and call getString on the array for each index:

val my_json = result.get().obj()
val items = my_json.getJSONArray("items")

for (i in 0 until items.length()) {
    val item = items.getString(i)
    // use item
}

If you don't want to deal with indexes while iterating, you could wrap the iteration of a JSONArray into an extension function:

fun JSONArray.forEachString(action: (String) -> Unit) {
    for (i in 0 until length()) {
        action(getString(i))
    }
}

Which could then be used like this:

val items = my_json.getJSONArray("items")
items.forEachString { item ->
    // use item
}

You could extend the JSONArray class with an iterator function as well if you really wanted to iterate the array with a regular for loop, but it would be more trouble than it's worth.

Use the keys() iterator to iterate over all the properties, and call get() for each.

Iterator<String> iter = json.keys();
while (iter.hasNext()) {
    String key = iter.next();
    try {
        Object value = json.get(key);
    } catch (JSONException e) {
        // Something went wrong!
    }
}

    try {
        JSONObject json = new JSONObject(data);
        Iterator<String> temp = json.keys();
        while (temp.hasNext()) {
            String key = temp.next();
            Object value = json.get(key);
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }

In my humble opinion, you can convert LearningEvent to JSONObject using .toJson. Here the sample code:

var learningEvents = db.learningEventDao().getAllLearningEvents(currentSessionId);
var returnCollection = emptyList<JSONObject>();
learningEvents.forEach{ element ->
      val singleObject = gson.toJson(element);
      returnCollection += JSONObject(singleObject);
}

There is no question that the future of parsing in Kotlin will be with kotlinx.serialization. It is part of Kotlin libraries. Version kotlinx.serialization 1.0 is finally released

https://github.com/Kotlin/kotlinx.serialization

Copyimport kotlinx.serialization.*
import kotlinx.serialization.json.Json

@Serializable
data class MyModel(val a: Int, @Optional val b: String = "42")

fun main(args: Array<String>) {

    // serializing objects
    val jsonData = Json.encodeToString(MyModel.serializer(), MyModel(42))
    println(jsonData) // {"a": 42, "b": "42"}
    
    // serializing lists
    val jsonList = Json.encodeToString(MyModel.serializer().list, listOf(MyModel(42)))
    println(jsonList) // [{"a": 42, "b": "42"}]

    // parsing data back
    val obj = Json.decodeFromString(MyModel.serializer(), """{"a":42}""")
    println(obj) // MyModel(a=42, b="42")
}