It certainly has been already asked but I wasn't able to search the solution for my case.
I have two JSON file : quizzes.json and quizzesQuestions.json. The first one only has the titles and id of every quizzes and the second one has all the datas needed for each quiz.
quizzes.json:
[
{
"_id": "1",
"title": "blabla"
},
{
"_id": "2",
"title": "blabla2"
},
{
"_id": "3",
"title": "blabla3"
},
{
"_id": "4",
"title": "blabla4"
}
]
and quizzesQuestions.json:
[
{
"quizId": "1",
"questions": [
{
"questionId": "1",
"translations": [
{
"lang": "fr",
"label": "Quelle est la reponse ?",
"answers": [
"reponse 1",
"reponse 2",
"reponse 3",
"reponse 4"
],
"trueAnswer": "reponse 1 2 3 or 4",
"explanation": "parce que..."
},
{
"lang": "en",
"label": "What is the answer ?",
"answers": [
"answer 1",
"answer 2",
"answer 3",
"answer 4"
],
"trueAnswer": "answer 1 2 3 or 4",
"explanation": "because..."
},
{
"lang": "de",
"label": "What is the answer ?",
"answers": [
"answer 1",
"answer 2",
"answer 3",
"answer 4"
],
"trueAnswer": "answer 1 2 3 or 4",
"explanation": "because..."
},
{
"lang": "sp",
"label": "What is the answer ?",
"answers": [
"answer 1",
"answer 2",
"answer 3",
"answer 4"
],
"trueAnswer": "answer 1 2 3 or 4",
"explanation": "because..."
}
]
},
{
"questionId": "2",
"translations": [
{
"lang": "fr",
"label": "Quelle est la reponse ?",
"answers": [
"reponse 1",
"reponse 2",
"reponse 3",
"reponse 4"
],
"trueAnswer": "reponse 1 2 3 or 4",
"explanation": "parce que..."
},
{
"lang": "en",
"label": "What is the answer ?",
"answers": [
"answer 1",
"answer 2",
"answer 3",
"answer 4"
],
"trueAnswer": "answer 1 2 3 or 4",
"explanation": "because..."
},
{
"lang": "de",
"label": "What is the answer ?",
"answers": [
"answer 1",
"answer 2",
"answer 3",
"answer 4"
],
"trueAnswer": "answer 1 2 3 or 4",
"explanation": "because..."
},
{
"lang": "sp",
"label": "What is the answer ?",
"answers": [
"answer 1",
"answer 2",
"answer 3",
"answer 4"
],
"trueAnswer": "answer 1 2 3 or 4",
"explanation": "because..."
}
]
}
]
}
]
I need to retrieve one object from a JSON file (for now, it will become a database in the future) which is equal to the a specific id. Here there is only one quiz with an id of 1.
I'm already able to retrieve every quizzes from the first file with Gson and display them in a list. Now I want to be able to retrieve only the quiz which has the same id as the one the user clicked on but I don't know how to proceed.
Here is my Gson code if it helps you understand what I want to do:
private void parseJSON() {
String quizzesString = loadJSONFromAsset();
try {
JSONArray array = new JSONArray(quizzesString);
if(array.length() > 0) {
Gson gson = new Gson();
int i = 0;
while(i < array.length()) {
quizzes.add(gson.fromJson(array.getJSONObject(i).toString(), Quizzes.class));
i++;
}
} else {
Log.d(TAG, "parseJSON: No Objects");
}
} catch (JSONException e) {
e.printStackTrace();
}
}
private String loadJSONFromAsset() {
String json;
try {
InputStream is = getApplication().getApplicationContext().getAssets().open("quizzes.json");
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
json = new String(buffer, "UTF-8");
} catch (IOException ex) {
ex.printStackTrace();
return null;
}
return json;
}
You can deserialise JSON directly from InputStream. Also, you do not need to use org.json to read JSON. Try to directly parse data using Gson:
private Map<String, Quizzes> loadQuizzes(InputStream jsonInputStream) throws IOException {
Gson gson = new GsonBuilder().create();
Type quizzesType = new TypeToken<List<Quizzes>>() {}.getType();
try (InputStreamReader reader = new InputStreamReader(jsonInputStream, StandardCharsets.UTF_8)) {
List<Quizzes> quizzes = gson.fromJson(reader, quizzesType);
return quizzes
.stream()
.collect(Collectors.toMap(Quizzes::getQuizId, q -> q));
}
}
Now, you can lookup Quizzes object from Map by id.
See also: