Konvertieren Sie ArrayList in JSONArray

StackOverflow https://stackoverflow.com/questions/4841952

Frage

Ich habe eine ArrayList, die ich in einem ArrayAdapter für eine ListView verwende.Ich muss die Elemente in der Liste nehmen und sie in ein JSONArray konvertieren, um sie an eine API zu senden.Ich habe mich umgesehen, aber nichts gefunden, was erklärt, wie dies funktionieren könnte. Jede Hilfe wäre willkommen.

UPDATE - LÖSUNG

Folgendes habe ich letztendlich getan, um das Problem zu lösen.

Objekt in ArrayList: 

public class ListItem {
    private long _masterId;
    private String _name;
    private long _category;

    public ListItem(long masterId, String name, long category) {
        _masterId = masterId;
        _name = name;
        _category = category;
    }

    public JSONObject getJSONObject() {
        JSONObject obj = new JSONObject();
        try {
            obj.put("Id", _masterId);
            obj.put("Name", _name);
            obj.put("Category", _category);
        } catch (JSONException e) {
            trace("DefaultListItem.toString JSONException: "+e.getMessage());
        }
        return obj;
    }
}

So habe ich es konvertiert: 

ArrayList<ListItem> myCustomList = .... // list filled with objects
JSONArray jsonArray = new JSONArray();
for (int i=0; i < myCustomList.size(); i++) {
        jsonArray.put(myCustomList.get(i).getJSONObject());
}

Und die Ausgabe: 

[{"Name":"Name 1","Id":0,"Category":"category 1"},{"Name":"Name 2","Id":1,"Category":"category 2"},{"Name":"Name 3","Id":2,"Category":"category 3"}]

Hoffe, das hilft jemandem eines Tages!

War es hilfreich?

Lösung

If I read the JSONArray constructors correctly, you can build them from any Collection (arrayList is a subclass of Collection) like so:

ArrayList<String> list = new ArrayList<String>();
list.add("foo");
list.add("baar");
JSONArray jsArray = new JSONArray(list);

References:

Andere Tipps

Use Gson library to convert ArrayList to JsonArray.

Gson gson = new GsonBuilder().create();
JsonArray myCustomArray = gson.toJsonTree(myCustomList).getAsJsonArray();

As somebody figures out that the OP wants to convert custom List to org.json.JSONArray not the com.google.gson.JsonArray,the CORRECT answer should be like this:

Gson gson = new Gson();

String listString = gson.toJson(
                    targetList,
           new TypeToken<ArrayList<targetListItem>>() {}.getType());

 JSONArray jsonArray =  new JSONArray(listString);

public void itemListToJsonConvert(ArrayList<HashMap<String, String>> list) {

        JSONObject jResult = new JSONObject();// main object
        JSONArray jArray = new JSONArray();// /ItemDetail jsonArray

        for (int i = 0; i < list.size(); i++) {
            JSONObject jGroup = new JSONObject();// /sub Object

            try {
                jGroup.put("ItemMasterID", list.get(i).get("ItemMasterID"));
                jGroup.put("ID", list.get(i).get("id"));
                jGroup.put("Name", list.get(i).get("name"));
                jGroup.put("Category", list.get(i).get("category"));

                jArray.put(jGroup);

                // /itemDetail Name is JsonArray Name
                jResult.put("itemDetail", jArray);
                return jResult;
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }

    }

I know its already answered, but theres a better solution here use this code :

for ( Field f : context.getFields() ) {
     if ( f.getType() == String.class ) || ( f.getType() == String.class ) ) {
           //DO String To JSON
     }
     /// And so on...
}

This way you can access variables from class without manually typing them..

Faster and better .. Hope this helps.

Cheers. :D

Add to your gradle: 

implementation 'com.squareup.retrofit2:converter-gson:2.3.0'

Convert ArrayList to JsonArray

JsonArray jsonElements = (JsonArray) new Gson().toJsonTree(itemsArrayList);
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