如何访问JSONArray中的JSONObject中的JSONObject？ Java /安卓

Question

I have this JSON file which I would like to use for my mobile application for my university project, however I'm having issues accessing the "fields" section of it and I'm not sure the best way to access it.

{"total_hits":47287,"max_score":11.854574,
"hits":[
{"_index":"f762ef22-e660-434f-9071-a10ea6691c27",
"_type":"item",
"_id":"513fceb375b8dbbc21000022",
"_score":11.854574,

    "fields":{
    "item_id":"513fceb375b8dbbc21000022",
    "item_name":"Cheese, cheddar - 1 cup, diced",       
    "brand_name":"USDA",    
    "nf_calories":533.28,
    "nf_total_fat":43.97,
    "nf_cholesterol":130.68,
    "nf_sodium":861.96,
    "nf_serving_size_qty":1,
    "nf_serving_size_unit":"serving"}},

{"_index":"f762ef22-e660-434f-9071-a10ea6691c27",
"_type":"item",
"_id":"513fceb375b8dbbc21000021",
"_score":11.800501,

     "fields":{"item_id":"513fceb375b8dbbc21000021",
     "item_name":"Cheese, cheddar - 1 cup, melted",
     "brand_name":"USDA",
     "nf_calories":985.76,
     "nf_total_fat":81.28,
     "nf_cholesterol":241.56,
     "nf_sodium":1593.32,
     "nf_serving_size_qty":1,
     "nf_serving_size_unit":"serving"}}, ... etc.

I can access the _Score value in the first section however, I am looking to access items like item_name, and nf_calories, however I'm not sure on the syntax. I believe I understand what I need to do, but I can't visualise it in my head.

JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("hits");


            List<NutritionModel> nutModelList = new ArrayList<>();


            for(int i=0; i<parentArray.length(); i++) {

                hitsObject = parentArray.getJSONObject(i);
                NutritionModel nutModel = new NutritionModel();

                nutModel.set_score(hitsObject.getDouble("_score"));


                //Adding final object in the list
                nutModelList.add(nutModel);

This is what I currently have in my ViewNutrition.java file.

public class NutritionModel {

private Double _score;

public Array getFieldarray() {
    return fieldarray;
}

public void setFieldarray(Array fieldarray) {
    this.fieldarray = fieldarray;
}

private Array fieldarray;
private String item_name;
private Double nf_calories;
private Double nf_total_fat;
private Double nf_protein;
private Double nf_cholesterol;
private Double nf_sodium;
private Double nf_serving_size_qty;


public Double get_score() {
    return _score;
}

    public void set_score(Double _score) {
    this._score = _score;
}

    public String getItem_name() {
        return item_name;
    }

    public void setItem_name(String item_name) {
        this.item_name = item_name;
    }

    public Double getNf_calories() {
        return nf_calories;
    }

    public void setNf_calories(Double nf_calories) {
        this.nf_calories = nf_calories;
    }

    public Double getNf_total_fat() {
        return nf_total_fat;
    }

    public void setNf_total_fat(Double nf_total_fat) {
        this.nf_total_fat = nf_total_fat;
    }

    public Double getNf_protein() {
        return nf_protein;
    }

    public void setNf_protein(Double nf_protein) {
        this.nf_protein = nf_protein;
    }

    public Double getNf_cholesterol() {
        return nf_cholesterol;
    }

    public void setNf_cholesterol(Double nf_cholesterol) {
        this.nf_cholesterol = nf_cholesterol;
    }

    public Double getNf_sodium() {
        return nf_sodium;
    }

    public void setNf_sodium(Double nf_sodium) {
        this.nf_sodium = nf_sodium;
    }

    public Double getNf_serving_size_qty() {
        return nf_serving_size_qty;
    }

    public void setNf_serving_size_qty(Double nf_serving_size_qty) {
        this.nf_serving_size_qty = nf_serving_size_qty;
    }
}

This is what's currently in my custom class for using the JSON data.

I've tried cycling through a JSONObject with a for statement, searching for a JSONObject called "fields" however it still just returns null results. Been stuck for a couple of days now and really struggling, any help or direction would be appreciated! Thanks.

Answer 1

The Field object isn't an Array it's an object. I suggest you create a FieldModel class and have the NutritionModel class contain an instance of the FieldModel class.

// In parser class
nutModel.setFields(hitsObject.getJSONObject("fields"));

// In NutritionModel class
public void setFields(JSONObject obj) {
  this.fields.item_name = obj.getString("item_name");
  // etc
}

Answer 2

In order to access items like item_name, and nf_calories use need to go to access the inner array. So, how to do-

JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("hits");

Suppose you need to access the elements(item_name etc.) of "hits" at index i then, you need to go to the inner JSONObject named "fields" and then you need to access the key named "item_name" for that do-

for(int i=0;i<parentArray.length();i++) {
    JSONObject obj1=parentArray.getJSONObject(i);
    JSONObject obj2= obj1.getJSONObject("fields");
    String item_name=obj2.getString("item_name");
}

Anyways even if you get confused in the explanation then for better JSON visualization access this website - http://jsonviewer.stack.hu/