Как распарсить вложенные JSON объекты?

Question

[awox]

Имеется json данные в файле https://www.cbr-xml-daily.ru/daily_json.js, они получены и обрабатываются:

val data = response.toString()
val valute = JSONObject(data).getJSONObject("Valute")
println(valute.toString())

До обработки:

{
    "Date": "2022-02-12T11:30:00+03:00",
    "PreviousDate": "2022-02-11T11:30:00+03:00",
    "PreviousURL": "\/\/www.cbr-xml-daily.ru\/archive\/2022\/02\/11\/daily_json.js",
    "Timestamp": "2022-02-13T23:00:00+03:00",
    "Valute": {
        "AUD": {
            "ID": "R01010",
            "NumCode": "036",
            "CharCode": "AUD",
            "Nominal": 1,
            "Name": "Австралийский доллар",
            "Value": 53.5105,
            "Previous": 53.7266
        },
...

После println(valute.toString()):

{
        "AUD": {
            "ID": "R01010",
            "NumCode": "036",
            "CharCode": "AUD",
            "Nominal": 1,
            "Name": "Австралийский доллар",
            "Value": 53.5105,
            "Previous": 53.7266
        },
...

Вопрос: Как пропарсить далее в глубину?
Как получить значения для каждой валюты для отображения в виде таблицы:

"ID" "NumCode" "CharCode" "Nominal" "Name" "Value" "Previous" 
AUD   "R01010"   "036"   "AUD"   1   "Австралийский доллар"   53.5105   53.7266
AZN   ...
GBP   ...

Answer 1

[Александр Прохорович]

А кто мешает дальше доставать объекты?
val aud = value.getJSONObject("AUD")

Comments

[awox]

Мешает нехватка знаний и опыта...

Тогда еще два вопроса в догонку:
1. Как получить список валют (из valute получить список AUD, AZN, GPB и т.д.)? Чтоб корректно отрабатывалось как изменение числа валют так и их названий?
2. Как из полученного объекта aud извлечь значения по ключу (типа: aud.getCharCode или еще как)?

[awox]

Со вторым пунктом вроде разобрался.

[Александр Прохорович]

Обычно есть возможность обхода результата выборки в цикле, пример можно вот тут увидеть:
https://www.tutorialspoint.com/how-to-iterate-a-js...

[awox]

Александр Прохорович, я попробовал сделать как тут: https://www.tutorialspoint.com/how-to-iterate-a-js...

val jsonObject = JSONObject(data)
val jsonArray = jsonObject.optJSONArray("Valute")
for (i in 0 until jsonArray.length()) {
val jsonObject = jsonArray.getJSONObject(i)
val charcode = jsonObject.optString("CharCode")
val name = jsonObject.optString("Name")
val value = jsonObject.optString("Value").toFloat()
strdata.append("Valute ").append(i).append(" : \n CharCode= ").append(charcode).append(" \n " + "Name= ")
.append(name).append(" \n Value= ").append(value).append(" \n\n ")
}

Но тут генерится такая ошибка:
Attempt to invoke virtual method 'int org.json.JSONArray.length()' on a null object reference.
Хотя в json файле вроде нет null значений.

[Александр Прохорович]

null object reference означает скорее всего, что jsonArray не создался, попробуйте поставить на второй строке точку останова и посмотреть, что находится в момент перед ошибкой в переменных jsonObject и jsonArray

[awox]

Александр Прохорович,
так и есть jsonArray = null. А почему он может не создаваться?

[Александр Прохорович]

awox, null возвращается, если не найдена строка поиска или если она не является массивом, напишите что попадает в jsonObject полностью

[awox]

Александр Прохорович,
Содержимое jsonObject:
{"Date":"2022-02-18T11:30:00+03:00","PreviousDate":"2022-02-17T11:30:00+03:00","PreviousURL":"\/\/www.cbr-xml-daily.ru\/archive\/2022\/02\/17\/daily_json.js","Timestamp":"2022-02-17T23:00:00+03:00","Valute":{"AUD":{"ID":"R01010","NumCode":"036","CharCode":"AUD","Nominal":1,"Name":"Австралийский доллар","Value":54.4662,"Previous":53.8301},"AZN":{"ID":"R01020A","NumCode":"944","CharCode":"AZN","Nominal":1,"Name":"Азербайджанский манат","Value":44.5866,"Previous":44.1519},"GBP":{"ID":"R01035","NumCode":"826","CharCode":"GBP","Nominal":1,"Name":"Фунт стерлингов Соединенного королевства","Value":102.8494,"Previous":101.6891},"AMD":{"ID":"R01060","NumCode":"051","CharCode":"AMD","Nominal":100,"Name":"Армянских драмов","Value":15.7818,"Previous":15.6198},"BYN":{"ID":"R01090B","NumCode":"933","CharCode":"BYN","Nominal":1,"Name":"Белорусский рубль","Value":29.4609,"Previous":29.362},"BGN":{"ID":"R01100","NumCode":"975","CharCode":"BGN","Nominal":1,"Name":"Болгарский лев","Value":44.032,"Previous":43.6535},"BRL":{"ID":"R01115","NumCode":"986","CharCode":"BRL","Nominal":1,"Name":"Бразильский реал","Value":14.7465,"Previous":14.539},"HUF":{"ID":"R01135","NumCode":"348","CharCode":"HUF","Nominal":100,"Name":"Венгерских форинтов","Value":24.2277,"Previous":24.1494},"HKD":{"ID":"R01200","NumCode":"344","CharCode":"HKD","Nominal":10,"Name":"Гонконгских долларов","Value":97.0915,"Previous":96.1621},"DKK":{"ID":"R01215","NumCode":"208","CharCode":"DKK","Nominal":1,"Name":"Датская крона","Value":11.5717,"Previous":11.4732},"USD":{"ID":"R01235","NumCode":"840","CharCode":"USD","Nominal":1,"Name":"Доллар США","Value":75.7527,"Previous":75.0141},"EUR":{"ID":"R01239","NumCode":"978","CharCode":"EUR","Nominal":1,"Name":"Евро","Value":86.1308,"Previous":85.306},"INR":{"ID":"R01270","NumCode":"356","CharCode":"INR","Nominal":10,"Name":"Индийских рупий","Value":10.0809,"Previous":10.0005},"KZT":{"ID":"R01335","NumCode":"398","CharCode":"KZT","Nominal":100,"Name":"Казахстанских тенге","Value":17.6786,"Previous":17.5533},"CAD":{"ID":"R01350","NumCode":"124","CharCode":"CAD","Nominal":1,"Name":"Канадский доллар","Value":59.5634,"Previous":59.1174},"KGS":{"ID":"R01370","NumCode":"417","CharCode":"KGS","Nominal":100,"Name":"Киргизских сомов","Value":89.3039,"Previous":88.4373},"CNY":{"ID":"R01375","NumCode":"156","CharCode":"CNY","Nominal":1,"Name":"Китайский юань","Value":11.9516,"Previous":11.841},"MDL":{"ID":"R01500","NumCode":"498","CharCode":"MDL","Nominal":10,"Name":"Молдавских леев","Value":42.1199,"Previous":41.7906},"NOK":{"ID":"R01535","NumCode":"578","CharCode":"NOK","Nominal":10,"Name":"Норвежских крон","Value":85.0428,"Previous":84.224},"PLN":{"ID":"R01565","NumCode":"985","CharCode":"PLN","Nominal":1,"Name":"Польский злотый","Value":19.1169,"Previous":19.0208},"RON":{"ID":"R01585F","NumCode":"946","CharCode":"RON","Nominal":1,"Name":"Румынский лей","Value":17.4152,"Previous":17.2859},"XDR":{"ID":"R01589","NumCode":"960","CharCode":"XDR","Nominal":1,"Name":"СДР (специальные права заимствования)","Value":106.2629,"Previous":105.0828},"SGD":{"ID":"R01625","NumCode":"702","CharCode":"SGD","Nominal":1,"Name":"Сингапурский доллар","Value":56.3175,"Previous":55.8182},"TJS":{"ID":"R01670","NumCode":"972","CharCode":"TJS","Nominal":10,"Name":"Таджикских сомони","Value":67.1269,"Previous":66.4724},"TRY":{"ID":"R01700J","NumCode":"949","CharCode":"TRY","Nominal":10,"Name":"Турецких лир","Value":55.6461,"Previous":55.0558},"TMT":{"ID":"R01710A","NumCode":"934","CharCode":"TMT","Nominal":1,"Name":"Новый туркменский манат","Value":21.6746,"Previous":21.4633},"UZS":{"ID":"R01717","NumCode":"860","CharCode":"UZS","Nominal":10000,"Name":"Узбекских сумов","Value":69.8498,"Previous":69.2193},"UAH":{"ID":"R01720","NumCode":"980","CharCode":"UAH","Nominal":10,"Name":"Украинских гривен","Value":26.8435,"Previous":26.7288},"CZK":{"ID":"R01760","NumCode":"203","CharCode":"CZK","Nominal":10,"Name":"Чешских крон","Value":35.311,"Previous":35.0459},"SEK":{"ID":"R01770","NumCode":"752","CharCode":"SEK","Nominal":10,"Name":"Шведских крон","Value":81.3696,"Previous":80.9991},"CHF":{"ID":"R01775","NumCode":"756","CharCode":"CHF","Nominal":1,"Name":"Швейцарский франк","Value":82.1613,"Previous":81.0613},"ZAR":{"ID":"R01810","NumCode":"710","CharCode":"ZAR","Nominal":10,"Name":"Южноафриканских рэндов","Value":50.519,"Previous":49.8019},"KRW":{"ID":"R01815","NumCode":"410","CharCode":"KRW","Nominal":1000,"Name":"Вон Республики Корея","Value":63.2841,"Previous":62.72},"JPY":{"ID":"R01820","NumCode":"392","CharCode":"JPY","Nominal":100,"Name":"Японских иен","Value":65.8061,"Previous":64.8098}}}