Android Json url if null

Question

Wondering if its way to check if the json url is null? by this I mean if url returning null and not json array/objects.

is there some way I can check it?

I have following code and I really wondering how I should do it.

class LoadAllGB extends AsyncTask<String, String, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mProgressDialog = new ProgressDialog(ListViser.this);
        mProgressDialog.setMessage("Vent Venligst..");
        mProgressDialog.setTitle("Henter");
        mProgressDialog.setIndeterminate(false);
        mProgressDialog.setCancelable(false);
        mProgressDialog.show();
    }

    protected String doInBackground(String... args) {
        DateFormat df = new SimpleDateFormat("dd-MM-yyyy");
        String dato = df.format(Calendar.getInstance().getTime());

        DateFormat df2 = new SimpleDateFormat("HH");
        String klok = df2.format(Calendar.getInstance().getTime());

        String url = "http://192.168.1.15";
        Log.w("leyth",  "Leyth" + url);
        JSONArray json = jParser.getJSONFromUrl(url);
        try {
            //listen tømmes
            for(int i = 0; i < json.length(); i++){
                    JSONObject c = json.getJSONObject(i);

                String time = c.getString(Tag_time);
                String cover = c.getString(Tag_cover);
                String artist = c.getString(Tag_artist);
                String title = c.getString(Tag_title);

                HashMap<String, String> map = new HashMap<String, String>();

                map.put(Tag_time, time);
                map.put(Tag_cover, cover);
                map.put(Tag_artist, artist);
                map.put(Tag_title, title);

                abcList.add(map);
            }
        } catch (JSONException e) {
            e.printStackTrace();
            Toast.makeText(getApplicationContext(), "this is my Toast message!!! =)",
                       Toast.LENGTH_LONG).show();  
            Log.e("JSON Parser fejl", "fejl da man prøve og hente data " + e.toString());
        }

        return null;
    }

    protected void onPostExecute(String file_url) { 

        if(file_url!=null)//Do your validation for result
        {
            Toast.makeText(getApplicationContext(), "this is my Toast message!!! =)",
                       Toast.LENGTH_LONG).show();  
        }
        if(mProgressDialog.isShowing()){
            mProgressDialog.dismiss();
        }
        // Locate the listview in listview_main.xml
        adapter = new ListViewAdapter(ListViser.this, abcList);
        // Binds the Adapter to the ListView
        listview.setAdapter(adapter);
        registerForContextMenu(listview);
    }
}

you are doing this in wrong way...you are not returning any file_url in your doInBackground(You are returning null),while you are accessing String file_url in onPost and checking on this that is already null.... — Rohit Goswami
– Rohit Goswami, Commented Jul 14, 2014 at 4:25
for jsonArray...if(json.length == 0){//jsonArrayEmpty}....and if(c.toString.isEmpty){//Then Json object null}.... — Rohit Goswami
– Rohit Goswami, Commented Jul 14, 2014 at 4:30

Hareshkumar Chhelana · Accepted Answer · 2014-07-14 05:07:35Z

1

Try this way,hope this will help you to solve your problem.

   protected String doInBackground(String... args) {
        DateFormat df = new SimpleDateFormat("dd-MM-yyyy");
        String dato = df.format(Calendar.getInstance().getTime());

        DateFormat df2 = new SimpleDateFormat("HH");
        String klok = df2.format(Calendar.getInstance().getTime());

        String url = "http://192.168.1.15";
        Log.w("leyth", "Leyth" + url);
        if(jParser.getJSONFromUrl(url)!=null && (jParser.getJSONFromUrl(url) instanceof JSONArray || jParser.getJSONFromUrl(url) instanceof JSONObject)) {
            if (jParser.getJSONFromUrl(url) instanceof JSONArray && ((JSONArray) jParser.getJSONFromUrl(url)).toString().length() <= 0) {
                return "";
            } else if (jParser.getJSONFromUrl(url) instanceof JSONObject && ((JSONObject) jParser.getJSONFromUrl(url)).toString().length() <= 0) {
                return "";
            } else if(jParser.getJSONFromUrl(url) instanceof JSONArray && ((JSONArray) jParser.getJSONFromUrl(url)).toString().length() > 0){
                try {
                    JSONArray json = jParser.getJSONFromUrl(url);

                    //listen tømmes
                    for (int i = 0; i < json.length(); i++) {
                        JSONObject c = json.getJSONObject(i);

                        String time = c.getString(Tag_time);
                        String cover = c.getString(Tag_cover);
                        String artist = c.getString(Tag_artist);
                        String title = c.getString(Tag_title);

                        HashMap<String, String> map = new HashMap<String, String>();

                        map.put(Tag_time, time);
                        map.put(Tag_cover, cover);
                        map.put(Tag_artist, artist);
                        map.put(Tag_title, title);

                        abcList.add(map);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(), "this is my Toast message!!! =)",
                            Toast.LENGTH_LONG).show();
                    Log.e("JSON Parser fejl", "fejl da man prøve og hente data " + e.toString());
                }
                return String.valueOf(abcList.size());
            }else{

                try {
                    JSONObject json = jParser.getJSONFromUrl(url);

                    String time = c.getString(Tag_time);
                    String cover = c.getString(Tag_cover);
                    String artist = c.getString(Tag_artist);
                    String title = c.getString(Tag_title);

                    HashMap<String, String> map = new HashMap<String, String>();

                    map.put(Tag_time, time);
                    map.put(Tag_cover, cover);
                    map.put(Tag_artist, artist);
                    map.put(Tag_title, title);

                    abcList.add(map);

                } catch (JSONException e) {
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(), "this is my Toast message!!! =)",
                            Toast.LENGTH_LONG).show();
                    Log.e("JSON Parser fejl", "fejl da man prøve og hente data " + e.toString());
                }
                return String.valueOf(abcList.size());
            }
        }else{
            return null;
        }
    }

    protected void onPostExecute(String file_url) {

        if(file_url!=null && file_url.length()>0)
        {
            // this is toast message for list with data
            Toast.makeText(getApplicationContext(), "this is my Toast message 1!!! =)",
                    Toast.LENGTH_LONG).show();
        }else if(file_url!=null && file_url.length()<=0){
            // this is toast message for empty list
            Toast.makeText(getApplicationContext(), "this is my Toast message 2!!! =)",
                    Toast.LENGTH_LONG).show();
        }else{
            // this is toast message for respone null
            Toast.makeText(getApplicationContext(), "this is my Toast message 3 !!! =)",
                    Toast.LENGTH_LONG).show();
        }
        if(mProgressDialog.isShowing()){
            mProgressDialog.dismiss();
        }
        // Locate the listview in listview_main.xml
        adapter = new ListViewAdapter(ListViser.this, abcList);
        // Binds the Adapter to the ListView
        listview.setAdapter(adapter);
        registerForContextMenu(listview);
    }

edited Jul 14, 2014 at 5:07

answered Jul 14, 2014 at 4:47

Hareshkumar Chhelana

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5 Comments

Shivam Verma Over a year ago

You don't really need this check I guess : jParser.getJSONFromUrl(url) instanceof JSONObject You're anyways going to convert it to JSONArray which'll generate an exception.

Hareshkumar Chhelana Over a year ago

i just gave alternative way to check and what you think i didn't know about it ?

Shivam Verma Over a year ago

Woah there tiger. Relax. Good for you if you knew.

Tirolel Over a year ago

Well its like how I wanted. no crash when there is no "json array/obj". But is there a way I can show a toast message when its empty?

Shivam Verma Over a year ago

@Neotrix Just add the toast message inside an else block of this if block :

if(jParser.getJSONFromUrl(url)!=null && (jParser.getJSONFromUrl(url) instanceof JSONArray || jParser.getJSONFromUrl(url) instanceof JSONObject)){ ... }

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