Parsing JSON data to string in Android app

Question

I connect a database on my server from the Android application and I want to use the info the server send back to me. Here is the response I get from the server :

[{"id":"1","userid":"1159448580","address":"Kishinev 3"}]

Here is my function that is realizing the connection to the server and trying to parse the response :

String checkForUserIdGetBookmarks (String returnString) {
        InputStream is = null;
        String result = "";
        //the userId data to send
        ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
        nameValuePairs.add(new BasicNameValuePair("userId", userId));

        //http post
        try{
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost(PHP_URL);
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();
        } catch(Exception e){
            Log.e("log_tag", "Error in http connection "+e.toString());
        }

        //convert response to string
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            result = sb.toString();
        } catch(Exception e) {
            Log.e("log_tag", "Error converting result "+e.toString());
        }

        //parse json data
        try {
            JSONArray jArray = new JSONArray(result);
            for (int i=0; i<jArray.length(); i++) {
                JSONObject json_data = jArray.getJSONObject(i);
                Log.i("log_tag","id: "+json_data.getInt("id")+
                        ", userid: "+json_data.getString("userid")+
                        ", address: "+json_data.getInt("address")
                        );
                //Get an output to the screen
                returnString += "\n\t" + jArray.getJSONObject(i);
            }
        } catch(JSONException e) {
            Log.e("log_tag", "Error parsing data "+e.toString());
        }

        return returnString;
    }

But when I try to show the already converted string it shows an empty string.

/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
            String returnString = "";
        checkForUserIdGetBookmarks(returnString);
        Toast useridToast = Toast.makeText(getApplicationContext(), returnString, Toast.LENGTH_LONG);
        useridToast.show();

Where would you suggest is my mistake and do you know other way of getting the response from the server into a string which I can use afterwards?

String returnString = ""; checkForUserIdGetBookmarks(returnString); this seems to be the error. You could change it to String returnString = checkForUserIdGetBookmarks(); or am i missing something? — lucapette
– lucapette, Commented Aug 1, 2011 at 13:54
My function checkForUserIdGetBookmarks(String string) requires a String to work properly. Even if I use this: returnString = checkForUserIdGetBookmarks(returnString); I still don't get a persed string but an empty one instead. — Stefan Doychev
– Stefan Doychev, Commented Aug 1, 2011 at 13:58
I was trying to say that you could change your function. The input string you use in your function doesn't seem an input to the function. — lucapette
– lucapette, Commented Aug 1, 2011 at 14:14

Cristian · Accepted Answer · 2011-08-01 14:14:47Z

2

Use:

String returnString = checkForUserIdGetBookmarks(); // and declare returnString inside the method

Instead of:

String returnString = "";
checkForUserIdGetBookmarks(returnString);

edited Aug 1, 2011 at 14:14

answered Aug 1, 2011 at 13:58

Cristian

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4 Comments

Stefan Doychev Over a year ago

If I use only String returnString = checkForUserIdGetBookmarks(returnString); if puts out an error - The local variable returnString may not have been initialized - If I use it as : String returnString = ""; returnString = checkForUserIdGetBookmarks(returnString); Nothing happens - I still receive and empty toast.

Stefan Doychev Over a year ago

Changed code to :

String returnString = checkForUserIdGetBookmarks();         Toast useridToast = Toast.makeText(getApplicationContext(), returnString, Toast.LENGTH_LONG); 	    useridToast.show();

And in the function : String checkForUserIdGetBookmarks() { InputStream is = null; String result = ""; String returnString = null; .... returnString += "\n\t" + jArray.getJSONObject(i); But still an empty toast - is the parsing function okay?

Cristian Over a year ago

Is it generating errors? I mean, what do you see when running logcat?

Stefan Doychev Over a year ago

It was generating an error... stupid me - I entered a string for the address and was expecting an int for response... thanks for the help!

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