ArrayList.add not working with AsyncTask

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.

ListView

ArrayList

ArryList

AsyncTask

ArrayList

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

ArrayList

AsyncTask

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

AsyncTask

onCreateView()

ArrayList

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.

AsyncTask

ArrayList

ArrayList

ArryaList

This my fragment class with AsyncTask Part

AsyncTask

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

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;
}
}


categotyAdapter = new CategoryAdapter(getContext(), mCategoryLst); lvCategory.setAdapter(categotyAdapter);

onPostExecute

categotyAdapter.notifyDataSetChanged();

mCategoryLst

onPostExecute

FetchDataTask

4 Answers
4

categotyAdapter = new CategoryAdapter(getActivity(), mCategoryLst);
lvCategory.setAdapter(categotyAdapter);


as per your code, what i see, make changes like below code, for Fragment OnCreateView() and OnPostExecuation of AysncTask class.

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();

categotyAdapter = new CategoryAdapter(getContext(), mCategoryLst);
lvCategory.setAdapter(categotyAdapter);
return view;
}


And in OpPostExecution

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


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

onPostExecute()

@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

OnCreateView()

onPostExecute()

You need to call notifyDataSetChanged() on your adapter when you have the data:

notifyDataSetChanged()

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));
}
categotyAdapter.notifyDataSetChanged();


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