ArrayList.add not working with AsyncTask

Issue

I'm using fragment view to show ListView in my Android Application. It is working perfectly when I manually enter ArrayList. But now I want to add JSON array to the ArryList in AsyncTask class and add that ArrayList to Adapter.

So I got JSON array and put It ArrayList. This process doing in the AsyncTask class.

I execute that AsyncTask class in onCreateView() method in Fragment. Then I set ArrayList to Adapter. But problem is there..

After execute AsyncTask class get my JSON array perfectly and add to the ArrayList. But when I try to add my ArrayList to Adapter. Then my ArryaList empty.

This my fragment class with AsyncTask Part

public class FragmentCategory extends Fragment {

private ListView lvCategory;
private CategoryAdapter categotyAdapter;
private List<Category> mCategoryLst;

View view;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    view = inflater.inflate(R.layout.fragment_category , container, false);
    lvCategory = (ListView) view.findViewById(R.id.listview_category);
    mCategoryLst = new ArrayList<>();
    /*mCategoryLst.add(new Category(1, "hghjj" ,null));
    mCategoryLst.add(new Category(2,"Abcd", null));
    mCategoryLst.add(new Category(3,"Aeec", null));*/
    new FetchDataTask().execute();
    if(mCategoryLst!=null && mCategoryLst.size()>0) {
        categotyAdapter = new CategoryAdapter(getContext(), mCategoryLst);
    }

    lvCategory.setAdapter(categotyAdapter);
    return view;
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //new FetchDataTask().execute();

}
public class FetchDataTask extends AsyncTask<String,String,Void>
{
    private ProgressDialog progressDialog = new ProgressDialog(getActivity());
    private String mUrlCategory;
    @Override
    protected void onPreExecute() {
        progressDialog.setMessage("Downloading your data...");
        progressDialog.show();
        progressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
            public void onCancel(DialogInterface arg0) {
                FetchDataTask.this.cancel(true);
            }
        });
    }

    @Override
    protected Void doInBackground(String... strings) {
        HttpURLConnection urlConnection = null;
        BufferedReader reader = null;
        Uri bUri = Uri.parse(getString(R.string.url_category));
        URL url;
        try {
            url = new URL(bUri.toString());
            urlConnection = (HttpURLConnection)url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();
            InputStream inputStream = urlConnection.getInputStream();
            StringBuffer buffer = new StringBuffer();

            if(inputStream==null)
            {
                return null;
            }

            reader = new BufferedReader(new InputStreamReader(inputStream));

            String line;
            while ((line = reader.readLine()) != null)
            {
                buffer.append(line + "\n");
            }

            if(buffer.length() == 0)
            {
                return null;
            }
            mUrlCategory = buffer.toString();                

        }
        catch (MalformedURLException e) {
        e.printStackTrace();
        } catch (IOException e) {
        e.printStackTrace();
        } /*catch (JSONException e) {
        e.printStackTrace();
        } */finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (final IOException e) {
                    Log.e("MainActivity", "Error closing stream", e);
                }
            }
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        try {
            if (progressDialog.isShowing())
                progressDialog.dismiss();
            JSONArray jArray = new JSONArray(mUrlCategory);
            for (int i = 0; i < jArray.length(); i++) {

                JSONObject jObject = jArray.getJSONObject(i);

                int id = Integer.parseInt(jObject.getString("id"));
                String name = jObject.getString("categoryName");
                String imageUrl = jObject.getString("iconPath");

                mCategoryLst.add(new Category(id, name ,null));
            }
    } catch (JSONException e) {
    Log.e("JSONException", "Error: " + e.toString());
} // catch (Exception e)
    }
}

}

This my Category class
This one using for create ArrayList

public class Category {

private  int categoryId;
private String categoryName;
private String imgUrl;

public Category()
{

}

public Category(int id,String name, String img)
{
    this.categoryId=id;
    this.categoryName=name;
    this.imgUrl=img;
}

//Gettert

public int getCategoryId() {
    return categoryId;
}

public String getCategoryName() {
    return categoryName;
}


public String getImgUrl() {
    return imgUrl;
}

//Settert


public void setCategoryId(int categoryId) {
    this.categoryId = categoryId;
}

public void setCategoryName(String categoryName) {
    this.categoryName = categoryName;
}

public void setImgUrl(String imgUrl) {
    this.imgUrl = imgUrl;
}
}

This my Adapter class

public class CategoryAdapter extends BaseAdapter {

private Context mContext;
private List<Category> mCategoryList;

//Constructor


public CategoryAdapter(Context mContext, List<Category> mCategoryList) {
    this.mContext = mContext;
    this.mCategoryList = mCategoryList;
}

@Override
public int getCount() {
    return mCategoryList.size();
}

@Override
public Object getItem(int position) {
    return mCategoryList.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View v = View.inflate(mContext, R.layout.item_category, null);
    TextView tvCategoryName = (TextView) v.findViewById(R.id.category_name);
    ImageView ivCategoryImg = (ImageView) v.findViewById(R.id.img_category);
    //Set Value
    tvCategoryName.setText(mCategoryList.get(position).getCategoryName());
    //ivCategoryImg.setImageResource();
    //Set ID
    v.setTag(mCategoryList.get(position).getCategoryId());

    return v;
}
}

Solution

Problem Solved I change my onPostExecute() method like this...

@Override
protected void onPostExecute(Void aVoid) {
    try {
        if (progressDialog.isShowing())
            progressDialog.dismiss();
        JSONObject jsonObject = new JSONObject(mUrlCategory);

        Log.v("Response", jsonObject.toString());

        JSONArray categoryArray = jsonObject.getJSONArray("itemcategory");
        for (int i = 0; i < categoryArray.length(); i++) {

            JSONObject jCategory = (JSONObject) categoryArray.get(i);

            int id = Integer.parseInt(jCategory.getString("id"));
            String name = jCategory.getString("categoryName");
            String imageUrl = jCategory.getString("iconPath");

            mCategoryLst.add(new Category(id, name, null));
        }

        if (mCategoryLst != null && mCategoryLst.size() > 0) {
            categotyAdapter = new CategoryAdapter(getContext(), mCategoryLst);
        }

        lvCategory.setAdapter(categotyAdapter);
        categotyAdapter.notifyDataSetChanged();
    } catch (JSONException e) {
        Log.e("JSONException", "Error: " + e.toString());
    } // catch (Exception e)
}

When I put this part

if (mCategoryLst != null && mCategoryLst.size() > 0) {
    categotyAdapter = new CategoryAdapter(getContext(), mCategoryLst);
}

lvCategory.setAdapter(categotyAdapter);

in OnCreateView() application not working. So I put It in onPostExecute(). Then It work perfectly. Thanks All

Answered By - Ayesh Ruwantha