JSONArray not returning data

Question

I am writing a JSONArray so as to return multiple data from the database for my android application.

I wrote the below code but it is not returning me any data at all as the error is java.lang.NullPointerException at this line: jArray = new JSONArray(result);

How can I change my code so that JSONArray works? Not very sure about how JSONArray works.

Thanks for the help in advance!

php file:

$user=$_POST["username"];

$query = "SELECT longitude,latitude FROM friends INNER JOIN coordinates ON friends.username = coordinates.username WHERE friends.friend_of='$user'";
$sql=mysqli_query($conn, $query);

if (!$sql) {
    echo 'Could not run query: ' . mysql_error();
    exit;
}

$rows = array();
while($r = mysqli_fetch_assoc($sql)) {
    $rows[] = $r;
}
print json_encode($rows);

JSONArray class:

List<NameValuePair> nameValuePairList = new ArrayList<NameValuePair>();
nameValuePairList.add(new BasicNameValuePair("username", username));
try {
    HttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost("http://powerbankk.16mb.com/check_if_friends.php");
    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairList));
    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);
    sb = new StringBuilder();
    sb.append(reader.readLine() + "\n");
    String line = "0";

    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());
}

//paring data
Double longitude, latitude;

try {
    jArray = new JSONArray(result);
    JSONObject json_data = null;

    for (int i = 0; i < jArray.length(); i++) {
        json_data = jArray.getJSONObject(i);
        longitude = json_data.getDouble("longitude");
        latitude = json_data.getDouble("latitude");
        System.out.println(longitude);
        System.out.println(latitude);
    }
} catch (JSONException e1) {
    Toast.makeText(getBaseContext(), "Location not found", Toast.LENGTH_LONG).show();
}

It doesn't look like the PHP is outputting a JSONArray, rather it would be a JSONObject. — justin shores, Sep 24 '15 at 17:12
possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — njzk2, Sep 24 '15 at 17:12
can you post some of the json output from that php just to be sure? — justin shores, Sep 24 '15 at 17:14
@justinshores [{"longitude":"103.9366229","latitude":"1.336459"},{"longitude":"103.930041","latitude":"1.324119"}] — Qing Yong, Sep 24 '15 at 17:21
ok, well it is an array, the result you posted, was that a log from the application, or via web? — justin shores, Sep 24 '15 at 17:31

score 0 · Answer 1 · answered Sep 24 '15 at 17:22

0

Try build in Function IOUtils.ToString() to convert stream to string

  InputStream is = new InputStream(is, "iso-8859-1");
     String result= IOUtils.toString( is );
       jArray = new JSONArray(result);

answered Sep 24 '15 at 17:22

Rajan Kali

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score 0 · Answer 2 · answered Sep 24 '15 at 17:38

i would try changing the last line of php to something like this:

print json_encode(Array("Posts" => $rows));

and modifying the Java to something like this:

//paring data
        Double longitude, latitude;

        try {
            JSONObject object = new JSONObject(result);
            jArray = object.getJSONArray("Posts"); // get specific array from php.
            JSONObject json_data = null;

            for (int i = 0; i < jArray.length(); i++) {
                json_data = jArray.getJSONObject(i);
                longitude = json_data.getDouble("longitude");
                latitude = json_data.getDouble("latitude");
                System.out.println(longitude);
                System.out.println(latitude);
            }

        } catch (JSONException e1) {
            Toast.makeText(getBaseContext(), "Location not found", Toast.LENGTH_LONG).show();
        }

@QingYong ok, well the value of result is obviously getting lost, try placing the JSON related code at the end of the `try` block containing `BufferedReader` since you were able to Log the value of result at some point it has to be valid at that point — justin shores, Sep 26 '15 at 15:18

JSONArray not returning data

2 Answers2