how to handle json exception occur inside asyntask

Question

Facing json exception when fetch value from database with empty result set

below is my code everything which is fine, only problem is i'm facing json exception when fetch value from database is empty. How i will handle this help me please i'm using asytask help me please what do i do? how to handle that???

public class fifthscreen extends Activity {
String num = null;
String _response;
// TextView ingredient;
private RatingBar ratingBar;
// TextView ingredient;
long Menu_ID;
String dish_ID;
View row4;
int IOConnect = 0;
View row3;
final private static int DIALOG_LOGIN = 1;
String status;
private static Handler handler;

ExpandableHeightGridView listview;

CategoryListAdapter3 cla;
String DescriptionAPI;

public Dialog dialog2;
public static int feedbacktype;
public static int myInt;

TextView txt1, txt2, txt3;
TextView ingredient;
ImageView img1;

String SelectMenuAPI;
DataBase db;
String FeedbackAPI;
String FeedbackAPI2;
static ArrayList<Long> Category_ID = new ArrayList<Long>();
static ArrayList<String> Category_name = new ArrayList<String>();
static ArrayList<String> Category_image = new ArrayList<String>();


ArrayList<Ingredient> ingredientList = new ArrayList<Ingredient>();

public static String allergen2;
private AQuery androidAQuery;
String name;
public static String FeedbackDishId;
String description;
String mainimage;
String allergen;
String url1;
View viewLoad;
String nutrition;
 String ingredientName;
  String ingredientSub;
  String formattedAsString;
Button FeedbackYummiSlice, FeedbackThisdish, nothanks;
final Context context = this;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fifthscreen);
    img1 = (ImageView) findViewById(R.id.test_button_image);

    txt1 = (TextView) findViewById(R.id.menuname);
    txt3 = (TextView) findViewById(R.id.description);
    ImageView b = (ImageView) findViewById(R.id.button1);
    ingredient = (TextView) findViewById(R.id.ingredient);

    Intent iGet = getIntent();
    ImageView options = (ImageView) findViewById(R.id.options5);
    androidAQuery = new AQuery(this);

    db = new DataBase(getBaseContext());
    try {
        db.createDataBase();
    } catch (IOException e1) {

        e1.printStackTrace();
    }

    options.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent iMenuList = new Intent(fifthscreen.this,
                    LinkButtons.class);
            startActivity(iMenuList);
        }
    });

    dish_ID = iGet.getStringExtra("dish_ID");

    listview = (ExpandableHeightGridView) findViewById(R.id.listview2);
    listview.setExpanded(true);

    cla = new CategoryListAdapter3(fifthscreen.this);
    new TheTask().execute();
    ImageView btnback = (ImageView) findViewById(R.id.btnback);

    btnback.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            finish();
        }
    });

    b.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            dialog2 = new Dialog(context);
            View vLoad = LayoutInflater.from(fifthscreen.this).inflate(
                    R.layout.timer, null);

            dialog2.setContentView(vLoad);

            FeedbackYummiSlice = (Button) dialog2
                    .findViewById(R.id.FeedbackYummiSlice);
            FeedbackThisdish = (Button) dialog2
                    .findViewById(R.id.FeedbackThisdish);
            nothanks = (Button) dialog2.findViewById(R.id.nothanks);




            dialog2.setTitle("FeedBack");

            TextView text = (TextView) dialog2.findViewById(R.id.text);
            text.setText(" I");

            dialog2.setCancelable(false);

            FeedbackYummiSlice.setOnClickListener(new OnClickListener() {
                public void onClick(View v) {

                    showDialog(DIALOG_LOGIN);
                    feedbacktype = 1;
                    FeedbackDishId = "0";

                }
            });

            FeedbackThisdish.setOnClickListener(new OnClickListener() {
                public void onClick(View v) {
                    //
                    showDialog(DIALOG_LOGIN);
                    feedbacktype = 2;
                    FeedbackDishId = dish_ID;

                }
            });

            nothanks.setOnClickListener(new OnClickListener() {
                public void onClick(View v) {
                    //
                    dialog2.dismiss();
                }
            });

            dialog2.show();
        }
    });

 }



public class TheTask extends AsyncTask<Void, String, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

    }

    @Override
    protected String doInBackground(Void... arg0) {

        return _response;
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);

            displayData();


        txt1.setText(name);
        txt3.setText(description);
        androidAQuery.id(img1).image(mainimage, true, true);



        listview.setAdapter(cla);
        cla.notifyDataSetChanged() ;




    }
}

@Override
protected Dialog onCreateDialog(int id) {

    AlertDialog dialogDetails = null;

    switch (id) {
    case DIALOG_LOGIN:
        LayoutInflater inflater = LayoutInflater.from(this);
        View dialogview = inflater.inflate(R.layout.dialog_layout, null);

        AlertDialog.Builder dialogbuilder = new AlertDialog.Builder(this);
        dialogbuilder.setTitle("Feedback Form");

        dialogbuilder.setView(dialogview);
        dialogDetails = dialogbuilder.create();

        break;
    }

    return dialogDetails;
}

@Override
protected void onPrepareDialog(int id, Dialog dialog) {

    switch (id) {
    case DIALOG_LOGIN:
        final AlertDialog alertDialog = (AlertDialog) dialog;
        Button Submit = (Button) alertDialog.findViewById(R.id.Submitbtn);
        Button cancelbutton = (Button) alertDialog
                .findViewById(R.id.btn_cancel);
        final EditText Email = (EditText) alertDialog
                .findViewById(R.id.Email);
        final EditText Comments = (EditText) alertDialog
                .findViewById(R.id.Comments);

        ratingBar = (RatingBar) alertDialog.findViewById(R.id.ratingBar);





    }
}









private void displayData()  {

    name ="";
    description ="";
    nutrition ="";
    allergen ="";
    mainimage ="";
    ingredientName ="";
    ingredientSub ="";
    formattedAsString="";

    Cursor mCursor = db
            .selectQuery("SELECT * ");

    if (mCursor.moveToFirst()) {
        do {

            name = (mCursor.getString(mCursor.getColumnIndex("name")));
            description 
         =(mCursor.getString(mCursor.getColumnIndex("description")));
            nutrition=(mCursor.getString(mCursor.getColumnIndex("nutrition")));
            allergen=(mCursor.getString(mCursor.getColumnIndex("allergen")));
            mainimage=(mCursor.getString(mCursor.getColumnIndex("image")));
        } while (mCursor.moveToNext());
    }

    mCursor.close();






    Cursor mCursor2 =  db.selectQuery("SELECT ");


    if (mCursor2.moveToFirst()) {
        do {
            ingredientName = mCursor2.getString(mCursor2.getColumnIndex("name"));
            ingredientSub = mCursor2.getString(mCursor2.getColumnIndex("sub_ingredients"));

            // create an Ingredient object in your loop and fill its
            // values
            Ingredient ingredientItem = new Ingredient();
            ingredientItem.setName(ingredientName);
            ingredientItem.setSub(ingredientSub);

            // Add your ingredient to your ingredientList
            ingredientList.add(ingredientItem);

        } while (mCursor2.moveToNext());
    }

    // Now you got a list of ingredients.
     formattedAsString = getFormattedIngredientList(ingredientList);
     ingredient.setText(Html.fromHtml(formattedAsString));

    mCursor2.close();





    Category_ID.clear();
    Category_name.clear();
    Category_image.clear();

    try {
    JSONArray jArray = new JSONArray(allergen);
    //
    for (int i = 0; i < jArray.length(); i++) {
        JSONObject object = jArray.getJSONObject(i);


        Category_ID.add((long) i);
        Category_name.add(object.getString("name"));
        Category_image.add(object.getString("image"));

    }




    JSONObject json = new JSONObject(nutrition);

final TableLayout table = (TableLayout) findViewById(R.id.table2);

                for (int j = 0; j < json.length(); j++) {

                    String s = String.valueOf(j + 1);

row3 = getLayoutInflater().inflate(R.layout.rows, null);
((TextView) row3.findViewById(R.id.localTime)).
       setText(json.getJSONObject(s).getString("qty"));
((TextView) row3.findViewById(R.id.apprentTemp)).

      setText(json.getJSONObject(s).getString("name"));

                    table.addView(row3);

                }




    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }




}



private String getFormattedIngredientList(ArrayList<Ingredient> ingredientList) {

    String concatProduct = "";
    for (int i = 0; i < ingredientList.size(); i++) {
        Ingredient currentIngredient = ingredientList.get(i);
                    if(currentIngredient.getSub() == null) {
                       currentIngredient.setSub("");  
                    }
        if (i == 0) {
            if ((currentIngredient.getSub() == null || 
  currentIngredient.getSub().equals(""))) {
                concatProduct = " " + "<b>" + currentIngredient.getName() + "</b>" + ", " + 
   currentIngredient.getSub();
            } else {
                concatProduct = " " + "<b>" + currentIngredient.getName() + "</b>" + ": " + 
  currentIngredient.getSub();
            }

        } else {
            if ((currentIngredient.getSub() == null || 
        currentIngredient.getSub().equals(""))) {
                if (i == ingredientList.size() - 1) {
                    concatProduct += " " + "<b>" + currentIngredient.getName() + "</b>" + 
           ". " + currentIngredient.getSub();
                } else {
                    concatProduct += " " + "<b>" + currentIngredient.getName() + "</b>" + 

         ", " + currentIngredient.getSub();
                }
            } else {
                concatProduct += " " + "<b>" + currentIngredient.getName() + "</b>" + ": " + currentIngredient.getSub();
            }
        }
    }

    return concatProduct;
}

   }


      **Following is exception:**

                 FATAL EXCEPTION: main
    java.lang.NullPointerException
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:112)
at org.json.JSONTokener.nextValue(JSONTokener.java:90)
at org.json.JSONArray.<init>(JSONArray.java:87)
at org.json.JSONArray.<init>(JSONArray.java:103)
at com.schoollunchapp.fifthscreen.displayData(fifthscreen.java:444)
at com.schoollunchapp.fifthscreen.access$0(fifthscreen.java:377)
at com.schoollunchapp.fifthscreen$TheTask.onPostExecute(fifthscreen.java:253)
at com.schoollunchapp.fifthscreen$TheTask.onPostExecute(fifthscreen.java:1)
at android.os.AsyncTask.finish(AsyncTask.java:417)
at android.os.AsyncTask.access$300(AsyncTask.java:127)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)

Answer 1

I think this occurred due to nullpointerexception.. you need to handle the nulls explicitly

if(mCursor!=null){
if (mCursor.moveToFirst()) {
                do {
                    name = (mCursor.getString(mCursor.getColumnIndex("name")));
                    description =(mCursor.getString(mCursor.getColumnIndex("description")));
                    nutrition=(mCursor.getString(mCursor.getColumnIndex("nutrition")));
                    allergen=(mCursor.getString(mCursor.getColumnIndex("allergen")));
                    mainimage=(mCursor.getString(mCursor.getColumnIndex("image")));
                } while (mCursor.moveToNext());
            }

}

And later also check

if(allergen!=null){
  JSONArray jArray = new JSONArray(allergen);
......
}