Troubles with JSON parsing

Question

I'm working on a simple news app. I need to fetch data from a remote server in JSON format then put it in view. I use TabLayout and recyclerView to display data categories and Volley for the query no API here.

The TabLayout is set automatically depending on data from JSON where I extract tabs title and the content of every tab is being displayed on recyclerView (Article title, image, content, links...) and rendered inside a fragment

I spent several hours trying to debug it without success., but whatever I do, no data is being displayed. Not sure what I'm doing wrong.

I know this is not the right place to ask for such things, but I'm a bit of a desperate and would need some experienced developer than me look at my problem.

How it works:

Activity launches BaseArticleFragment which calls a method that loads contents categories and bind the data to the views:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    this.fm = getSupportFragmentManager();
    this.baseArticleFragment = new BaseArticleFragment();
    FragmentTransaction ft = this.fm.beginTransaction();
    ft.add(R.id.fragment_container, this.baseArticleFragment, TAB_LAYOUT_FRAGMENT_TAG); 
    ft.commit();
}

When launched, baseArticleFragment calls loadCategories() method inside its onActivityCreated() method:

@Override
public void onActivityCreated(Bundle savedInstanceState){
    super.onActivityCreated(savedInstanceState);
    loadCategories();
}

here is the loadCategories() method:

private void loadCategories(){
    String url = "http://somesite.com/categories"; //link to grab the json data
    ApplicationController.getInstance().addToRequestQueue(
            new JsonObjectRequest(0, url, null, new Listener<JSONObject>() { //0 is the Volley code for GET method
                @Override
                public void onResponse(JSONObject jsonObject) {
                    BaseArticleFragment.categories = JSONParser.parseCategories(jsonObject);
                    BaseArticleFragment.this.mViewPager.setAdapter(
                            new RecyclerViewFragmentPagerAdapter(BaseArticleFragment.this.getChildFragmentManager(),
                                    BaseArticleFragment.categories));
                    BaseArticleFragment.this.mTabLayout.setupWithViewPager(BaseArticleFragment.this.mViewPager);
                }
            }, new Response.ErrorListener() {
                    @Override
                   public void onErrorResponse(VolleyError vError){
                        Log.d("BaseArticleFragment", "---Volley Error---");
                        Snackbar.make(BaseArticleFragment.this.mTabLayout, R.string.error_load_categories, Snackbar.LENGTH_SHORT)
                                .setAction(R.string.action_retry, new View.OnClickListener() {
                                    @Override
                                    public void onClick(View v) {
                                        BaseArticleFragment.this.loadCategories();
                                    }
                                }).show();
                    }
                }));
}

I guess the problem may be with the query but not sure cause I think my logic here is good

EDIT :

Here is the JSON data I need to fetch:

[
  {
    "name": "Topic 1",
    "tid": "2",
  },
  {
    "name": "Topic 2",
    "tid": "3",
  },
  {
    "name": "Topic 3",
    "tid": "4",
  },
  {
    "name": "Topic 4",
    "tid": "5",
  },
  {
    "name": "Topic 5",
    "tid": "6",
  },
  {
    "name": "Topic 6",
    "tid": "1415",
  },
  {
    "name": "Topic 7",
    "tid": "1414",
  },
  {
    "name": "Topic 8",
    "tid": "1298",
  },
  {
    "name": "Topic 9",
    "tid": "1301",
  },
  {
    "name": "Topic 10",
    "tid": "1299",
  },
  {
    "name": "Topic 11",
    "tid": "1302",
  },
  {
    "name": "Topic 12",
    "tid": "1300",

  },
  {
    "name": "Topic 13",
    "tid": "1297",
  }
]

Edit 2: I forget to paste the code for parseCategories() in my JSONPArser class

 public static ArrayList<Category> parseCategories(JSONObject jsonObject) {
    ArrayList<Category> categoryArrayList = new ArrayList<>();
    try {
        JSONArray categories = jsonObject.getJSONArray("categories");
        Category all = new Category();
        all.setTid("0");
        all.setName(ApplicationController.getInstance().getString(R.string.tab_all));
        categoryArrayList.add(all);
        for (int i = 0; i < categories.length(); i++) {
            JSONObject catObject = categories.getJSONObject(i);
            Category category = new Category();
            category.setTid(catObject.getString("tid"));
            category.setName(catObject.getString("name"));              
            categoryArrayList.add(category);
        }
        return categoryArrayList;

    } catch (JSONException e) {
        e.printStackTrace();
        return null;
    }

}

Have you checked that you are getting a success response and not an error? — theblitz, Apr 23 '19 at 11:35
There is no error code on the log, but the snackbar on the onErrorResponse(VolleyError vError) got triggered — esQmo_, Apr 23 '19 at 11:42
In that case, check in "volleyError" to see what error code is returned — theblitz, Apr 23 '19 at 11:55
That's strange. If it is entering the error Response code then there must be something in vError that says what it is. Try looking here: https://stackoverflow.com/questions/24700582/handle-volley-error and here: https://stackoverflow.com/questions/21867929/android-how-handle-message-error-from-the-server-using-volley/21868734#21868734 for examples of how to identify exactly what type of error it is. — theblitz, Apr 23 '19 at 12:11
I followed the recommendation from the suggested question and I'm getting timeout error — esQmo_, Apr 23 '19 at 12:26

Brahma Datta · Accepted Answer · 2019-04-24T14:37:35.237

Try this @esQmo_,

StringRequest stringRequest = new StringRequest(url , new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {

                try {
                    JSONArray jsonArray = new JSONArray(response);

                    ArrayList<Hashmap<String,String>> arraylist = new 
                                                            ArrayList<>();
                    for (int i = 0; i < jsonArray.length(); i++) {

                    HashMap<String, String> hashMap = new HashMap<>();
               String name = 
                      jsonArray.getJSONObject(i).getString("name");
                     String tid = 
                     jsonArray.getJSONObject(i).getString("tid");

                     hashMap.put("name", name);
                     hashMap.put("tid ", tid ); 
                     arraylist.add(hashMap);
                     Log.e("response",name + "\n" + tid);
                   }

              attachAdapter(arraylist);

                } catch (JSONException e) {
                    e.printStackTrace();
                }


            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

            }
        });

        RequestQueue queue = Volley.newRequestQueue(this);
        queue.add(stringRequest);

     //setting adapter data to the RecyclerView
    private void attachAdapter(ArrayList<HashMap<String, String>> 
    arrayList) {

    ExampleAdapter adapter = new ExampleAdapter(arrayList,this);
    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    recyclerView.setAdapter(adapter);
    adapter.notifyDataSetChanged();
 }
}

This is the adapter class

public class ExampleAdpater extends RecyclerView.Adapter<ExampleAdpater.ExampleViewHolder>{

public ArrayList<HashMap<String,String>> arraylist;

public Context context;

public ExampleAdpater(ArrayList<HashMap<String, String>> arraylist, Context context) {
    this.arraylist= arraylist;
    this.context = context;
}

@NonNull
@Override
public ExampleViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
    View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.textLayout,viewGroup,false);
    return new ExampleViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull ExampleViewHolder viewHolder, int i) {

    HashMap<String,String> hashMap = arraylist.get(i);
    viewHolder.name.setText(hashMap.get("name"));
    viewHolder.tid.setText(hashMap.get("tid"));

}

@Override
public int getItemCount() {
    return arraylist.size();
}

public class ExampleViewHolder extends RecyclerView.ViewHolder{

    TextView name,tid;

    public ExampleViewHolder(@NonNull View itemView) {
        super(itemView);

        name = itemView.findViewById(R.id.name);
        tid = itemView.findViewById(R.id.tid);

        name.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(v.getContext(), ""+name.getText().toString(), 
          Toast.LENGTH_SHORT).show();
            }
        });

        }
   }
  }

textLayout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/name"
    />

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/tid"
    />


</LinearLayout>

This way works, but remember: I'm adding the response to categories which is a BaseArticleFragment object (protected static ArrayList categories = null;) then set my Adapter — esQmo_, Apr 23 '19 at 12:55
As I tried to explain in my question, no data is being shown on the views. The activity is blank and I get Volley Error timed out — esQmo_, Apr 23 '19 at 12:58
Did you check putting my whole answer? I mean it works fine for me when i use the volley this way — Brahma Datta, Apr 23 '19 at 13:01
My approach is quite different. I have the same on my parseCategories() method — esQmo_, Apr 23 '19 at 13:05
we can do it easily by using Hashmap @esQmo_ . I can modify the answer for you by using HashMap concept. — Brahma Datta, Apr 24 '19 at 05:45
I'm using a set somewhere. Will you mind looking into the whole project? — esQmo_, Apr 24 '19 at 07:46
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/192300/discussion-between-g-brahma-datta-and-esqmo). — Brahma Datta, Apr 24 '19 at 08:00

George Gigauri · Answer 2 · 2019-04-23T12:40:41.927

1

You forgot to add this thing at the end of the "load" method:

Volley.newRequestQueue(this).add(jsonRequest);

Try to add it...

Instead of using new RequestQueue, please use RequestQueue jsonQueue = new RequestQueue

Like this:

    RequestQueue requestQueue = Volley.newRequestQueue(this);
        String url = "https://someurl.com/api";
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(url, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {

JSONArray ja = new JSONArray(response);

for(int i = 0; i < ja.length(); i++)
{
       JSONObject jo = ja.get(i);

       String name = jo.getString("name");
}

        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e("LOG", error.toString());
            }
        });
        requestQueue.add(jsonObjectRequest);

edited Apr 23 '19 at 12:40

answered Apr 23 '19 at 11:21

George Gigauri

55
1
9

Something isn't working, I can only get the error from the snackbar, – esQmo_ Apr 23 '19 at 11:40
@esQmo_ Error on Snackbar? I see you're working in the Fragment, in fragment, instead of activity.this, please use getActivity() – George Gigauri Apr 23 '19 at 11:43
Yes I modified it, although the IDE is warning it might be null – esQmo_ Apr 23 '19 at 11:44
But it's basically what I'm doing, I have an ApplicationController class – esQmo_ Apr 23 '19 at 11:46
No I have a white screen and always the message from snackbar, so error from Volley I guess? – esQmo_ Apr 23 '19 at 11:46
Ohh, it's a snackbar, it needs 'View', not context as the first parameter, please use findViewById(R.id.yourLayoutId); and try again – George Gigauri Apr 23 '19 at 11:50
Oh, the snackbar I use to display a message when something goes wrong such no article could be loaded and it is showing fine with that message – esQmo_ Apr 23 '19 at 11:53
@esQmo_ I think you have something wrong in onResponse method. try to use JSONArray ja = response.getJsonArray(); – George Gigauri Apr 23 '19 at 11:57
What should this do? – esQmo_ Apr 23 '19 at 12:08
Converts your JSON from url to JSONArray – George Gigauri Apr 23 '19 at 12:37
The problem could be that I'm facing a TimmeOut error – esQmo_ Apr 23 '19 at 12:42
@esQmo_ I edited my code once again, this code gets JSON Object (for example, name, I mean Topic 1) to String, then you can use this string whenever and where you want... Try it – George Gigauri Apr 23 '19 at 12:42
By the way, such request work. But I'm adding the response to categories, which is a BaseAarticleFragment object (protected static ArrayList categories = null;) – esQmo_ Apr 23 '19 at 12:53
@esQmo_ So you are adding it to your custom arraylist you say? – George Gigauri Apr 23 '19 at 12:56
Yes, could you look my whole project? To have a better understanding – esQmo_ Apr 23 '19 at 22:17

score 0 · Answer 3 · answered Apr 23 '19 at 11:15

0

Just check if you have set LayoutManager for recyclerView

recyclerView.setLayoutManager(new LinearLayoutManager(MyActivity.this));

answered Apr 23 '19 at 11:15

Kishita Variya

810
9
19

score 0 · Answer 4 · answered Apr 23 '19 at 11:17

0

Can we have your code and JSON data too? Since we can't read what's on your mind or on your computer... Plase make some edits to your post, add code and json data so we may help you.

answered Apr 23 '19 at 11:17

George Gigauri

55
1
9

score 0 · Answer 5 · answered Apr 23 '19 at 12:34

0

Since you are getting a timeout error you can change the timeout value so that it will be willing to wait longer.

Try something like this:

jsonObjectRequest.setRetryPolicy(new DefaultRetryPolicy(
MY_SOCKET_TIMEOUT_MS, 
DefaultRetryPolicy.DEFAULT_MAX_RETRIES, 
DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));

where MY_SOCKET_TIMEOUT_MS is amount of time (in milliseconds) you want to wait before a timeout. Start with 5000 (5 seconds) and play around with it.

Do this before

requestQueue.add(jsonObjectRequest);

answered Apr 23 '19 at 12:34

theblitz

6,683
16
60
114

Tried adding the lines and playing with value, didn't work. The error message appear as soon as the activity is launched – esQmo_ Apr 23 '19 at 12:41
You could try moving it to onAttach since that happens earlier but not sure if that will help – theblitz Apr 23 '19 at 12:54

Troubles with JSON parsing

5 Answers5