将ArrayList <MyCustomClass>转换为JSONArray

Question

我有一个ArrayList,我在ArrayAdapter中使用ListView.我需要获取列表中的项目并将它们转换为JSONArray以发送到API.我已经四处寻找,但没有找到任何解释这可行的方法,任何帮助都会受到赞赏.

更新 - 解决方案

以下是我最终要解决的问题.

ArrayList中的对象:

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;
    }
}

这是我如何转换它:

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());
}

并输出:

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

希望有一天能帮助别人!

Answer 1

如果我正确读取了JSONArray构造函数,你可以从任何Collection构建它们(arrayList是Collection的子类),如下所示:

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

参考文献:

• jsonarray构造函数:http: //developer.android.com/reference/org/json/JSONArray.html#JSONArray%28java.util.Collection%29
• 集合:http: //developer.android.com/reference/java/util/Collection.html

Answer 2

使用Gson库将ArrayList转换为JsonArray.

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

Answer 3

由于有人发现OP想要将自定义List转换为org.json.JSONArray不是com.google.gson.JsonArray,因此CORRECT答案应如下所示:

Gson gson = new Gson();

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

 JSONArray jsonArray =  new JSONArray(listString);

Answer 4

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();
            }
        }

    }