Android: get child of Object

Question

My code is :

Object value = tasks.get(key);

result value is : [{"name":"one","family":"yes"},{"name":"two","family":"no"}]

Now i want get child of value in foreach

foreach(...){
    String name = ...
    String family = ...
}

get that Object converted into a jSON array and iterate over it and get each object out of it and read the string values! or simply go POJO making and GSON lib use! — Rizwan Atta, Jul 06 '18 at 08:51
foreach not applicable to type JSONArray. [Check this](https://stackoverflow.com/questions/35771392/why-for-each-loop-is-not-applicable-for-json-array) You have to manually parse the response or have to use Gson library. — Viraj Patel, Jul 06 '18 at 09:04

Prexx · Accepted Answer · 2018-07-06T09:03:20.587

4

Your value is in JSONArray format.

Use this:

JSONArray values = new JSONArray((String) tasks.get(key)); // or alternative task.getString(key)
for (int i = 0; i < values.length(); i++) {
  JSONObject entry = values.getJSONObject(i);
  String name = entry.getString("name");
  String family = entry.getString("family");
}

edited Jul 06 '18 at 09:03

answered Jul 06 '18 at 08:51

Prexx

2,959
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I get this error `org.json.JSONException: Not a primitive array: class org.json.JSONArray` – salari mameri Jul 06 '18 at 09:00
print `tasks.get(key)` before you parse it. Make sure it starts from `[` and not `{` – isamirkhaan1 Jul 06 '18 at 09:01
I added a String cast. I don't know what your task ist. Maybe there is a `task.getString(key)` too. – Prexx Jul 06 '18 at 09:02
I get error now : `java.lang.ClassCastException: org.json.JSONArray cannot be cast to java.lang.String` – salari mameri Jul 06 '18 at 09:06

Anton A. · Answer 2 · 2018-07-06T09:02:56.300

0

Object itself not containig fields or something, you have to create pojo (just if you want clean and resuseble code) in order to get fields from it, for example, using Gson

Add dependencies:

dependencies {
    implementation 'com.google.code.gson:gson:2.8.5'
}

Add pojo:

public class Pojo{
   @SerializedName("name")
   @Expose
   private String name;
   @SerializedName("family")
   @Expose
   private String family;
}

Convert:

Gson gson = new Gson();
Pojo pojo = gson.fromJson(jsonObject.toString(), Pojo.class);

edited Jul 06 '18 at 09:02

answered Jul 06 '18 at 08:52

Anton A.

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@B001ᛦin order to reuse it, and not copy paste code to reuse it, or in order to not write code to parse json, or in order to not add more code to parse json when new fields arrived. – Anton A. Jul 06 '18 at 08:59
@B001ᛦ I provided edit, you also could/ – Anton A. Jul 06 '18 at 09:03

score 0 · Answer 3 · answered Jul 06 '18 at 09:00

Step 1: Convert Object instance into String

String response = (String) value;

Step 2: Feed the String instance into JsonArray

//don't forget to caught JSONException here
JsonArray array = new JsonArray(response);

Step 3: Iterate through JsonArray and get values from each JsonObject

  for (int i = 0; i < array.length(); i++) {
           JSONObject object = array.getJSONObject(i);

           //get values here
           String name = object.getString("name");
           String family = object.getString("family");
        }

Now, the whole code should look like this

 try {
        JSONArray array = new JSONArray("");
        for (int i = 0; i < array.length(); i++) {
           JSONObject object = array.getJSONObject(i);
           String name = object.getString("name");
           String family = object.getString("family");
        }
    } catch (JSONExceptione) {
      //do something..
    }

Important If you still don't know what happened, this whole process is called JSON parsing. Learn about it.

Android: get child of Object

3 Answers3