CODEWITHSUNDEEP
javaandroidarraysjson
Anil Shrestha
Anil Shrestha

Reputation: 1200

add value to json object in for loop java

I have defined new json object and array.

 private JSONArray array = new JSONArray();
 private JSONObject obj = new JSONObject();

Then i tried to fetch some data form firebase in loop and tried to put it in the defined json object and that object in defined json array. below is my code

for(int i = 1; i < 13; i++){
        String str = Integer.toString(i);
        mRef.child("calendar").child(str).child("start_date").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                start_date = dataSnapshot.getValue().toString();

                try {
                    obj.put("start_date", start_date);
                } catch (JSONException e) {
                    e.printStackTrace();
                }

                Log.d("start_date", start_date);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
        mRef.child("calendar").child(str).child("end_date").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                end_date = dataSnapshot.getValue().toString();

                try {
                    obj.put("end_date", end_date);
                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
        Log.d("obje", "" + obj);
        array.put(obj);

    }

    Log.d("arrary", "" + array);

But when I log my array or object it shows empty. Below is a log of json object of a single loop. D/obje: {} and this is my array after loop. D/arrary: [{},{},{},{},{},{},{},{},{},{},{},{}]

But when I log my object inside onDataChange class it logs data. but when I log at the end of loop it shows empty.

And this is log of start date to show that data is comming from firebase D/start_date: 09/17/2016

Upvotes: 2

Views: 3557

Answers (1)

Muthukrishnan Rajendran
Muthukrishnan Rajendran

Reputation: 11642

The problem is you are trying to get the value from the asynchronous callback. You're for loop will end before you get the callback from asynchronous request so it's showing empty.

Try like this,

for(int i = 1; i < 13; i++){
    String str = Integer.toString(i);
    mRef.child("calendar").child(str).addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String start_date = (String) dataSnapshot.child("start_date").getValue();
            String end_date = (String) dataSnapshot.child("end_date").getValue();

            try {

                JSONObject jsonObject = new JSONObject();
                jsonObject.put("start_date", start_date);
                jsonObject.put("end_date", end_date);

                Log.d("obje", "" + jsonObject);

                array.put(jsonObject);

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

            Log.d("start_date", start_date);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

Upvotes: 1

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