Android : String method return Null

Question

I know that this Question is repeated but I can't find the answer in Internet.

02-10 11:03:28.465 22410-22767/com.eztimetable.eztimetable I/System.out﹕ ERROR : null 02-10 11:03:28.465 22410-22767/com.eztimetable.eztimetable I/System.out﹕ error 02-10 11:03:28.595 22410-22410/com.eztimetable.eztimetable E/log_tag﹕ Error parsing data org.json.JSONException: Value error of type java.lang.String cannot be converted to JSONArray

why am i getting error / null ?

Below is the method that i use

//in LecturerScreen class
    public String getDataFromDB() {
    try {
        httpclient = new DefaultHttpClient();
        httppost= new HttpPost("http://192.168.1.9/my_folder_inside_htdocs/retrieve.php"); // make sure the url is correct.
        //add your data
        nameValuePairs = new ArrayList<NameValuePair>(2);
        // Always use the same variable name for posting i.e the android side variable name and php side variable name should be similar,
        nameValuePairs.add(new BasicNameValuePair("inputUser",inputUser.getText().toString().trim()));  // $Edittext_value = $_POST['Edittext_value'];
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
        ResponseHandler<String> responseHandler = new BasicResponseHandler();
        final String response = httpclient.execute(httppost,responseHandler);

        return response.trim();

    } catch (Exception e) {
        System.out.println("ERROR : " + e.getMessage());
        return "error";
    }
}

and this is how i call the method

    //in LecturerTimetable class
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_lecturer_timetable);

    tl = (TableLayout) findViewById(R.id.maintable);

    final LecturerScreen getdb = new LecturerScreen();

    new Thread(new Runnable() {
        public void run() {
            data = getdb.getDataFromDB();
            System.out.println(data);

            runOnUiThread(new Runnable() {

                @Override
                public void run() {
                    ArrayList<TimetableDisplay> timetable = parseJSON(data);
                    addData(timetable);
                }
            });

        }
    }).start();
}

I dont know what where my wrong here. Could someone give me solution for this question.

I am very new in developing Android program, so if anyone could guide, it would be an honor. Sorry for bad english. Thank you.

--UPDATE--

the php script

<?php
$hostname_localhost ="localhost";
$database_localhost ="eztimetable";
$username_localhost ="root";
$password_localhost ="";
$localhost = mysql_connect($hostname_localhost,$username_localhost,$password_localhost)
or
trigger_error(mysql_error(),E_USER_ERROR);

mysql_select_db($database_localhost, $localhost);

$lecturerUser = $_POST['inputUser'];
$query_search = "select lecturerCode from lectureraccount where lecturerId = '".$lecturerUser."'";
$query_exec = mysql_query($query_search,$localhost) or die(mysql_error());
while($row=mysql_fetch_assoc($query_exec))
        $json_output[]=$row;

print(json_encode($json_output));

mysql_close();

?>

Hi prudhvi , what should i do ? can you give some solution? sorry , i am very new to programming.. — SkyClasher
– SkyClasher, Commented Feb 10, 2015 at 3:27
My bad, I see you're returning 'response.trim()'. But check if your response is referring to null. Add 'Log.w("String", response);' just below final String response = httpclient.execute(httppost,responseHandler); and paste the Log message you get. — Prudhvi
– Prudhvi, Commented Feb 10, 2015 at 3:30
I add the line and it gives the same Log message as in the question. — SkyClasher
– SkyClasher, Commented Feb 10, 2015 at 3:47
@SkyClasher What kind of response are you expecting from the URL? — ifeomaro
– ifeomaro, Commented Feb 10, 2015 at 4:24

ifeomaro · Accepted Answer · 2015-02-11 22:52:00Z

1

You are seeing this error (Error parsing data org.json.JSONException: Value error of type java.lang.String cannot be converted to JSONArray) because your response is a JSONArray and you are treating it as a String. In order to get rid of the error, replace return response.trim(); with return response;. Since you are already processing the JSON response in your activity's onCreate using parseJSON(data), I think that should fix the problem.

Let me know if it does.

Edit

Try removing the ResponseHandler and executing the request without it:

HttpResponse response = httpclient.execute(httppost);
String responseString = EntityUtils.toString(response.getEntity());
int responseCode = response.getStatusLine().getStatusCode();

Also, change the way you instantiated the nameValuePairs. Remove the "2" and just instantiate it like this:

nameValuePairs = new ArrayList<NameValuePair>();

Edit 2

You should always "sanitize" the user's input. In your case, you needed to confirm that the user's input was not empty.

String inputUserString = inputUser.getText().toString().trim();

if (!inputUserString.isEmpty()) {
    // execute the httppost request here

} else {
    // display an error message to the user

}

edited Feb 11, 2015 at 22:52

answered Feb 10, 2015 at 15:51

ifeomaro

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16 Comments

SkyClasher Over a year ago

Error:(178, 49) error: incompatible types: HttpResponse cannot be converted to String when i try remove the ResponseHandler . i change the way i instantiated the nameValuePairs and still get the same error.

ifeomaro Over a year ago

I see where your problem is. response is of type HttpResponse and not String. I have updated my answer.

SkyClasher Over a year ago

the error is still the same, i still getting null.. But i found something, if i remove nameValuePairs , i will get the respons, but i need nameValuePairs to parse my inputUser to my php file. Do you have any idea how to solve this?

ifeomaro Over a year ago

How did you declare nameValuePairs and inputUser?

SkyClasher Over a year ago

This is how i declared it .EditText inputUser; List<NameValuePair> nameValuePairs; inputUser =(EditText) findViewById(R.id.inputId);

|

user1302353 · Accepted Answer · 2015-02-10 03:49:48Z

0

Before you use 'response.trim()', you need to check if your response is referring to null:

final String response = httpclient.execute(httppost,responseHandler);
if (response != null) {
    response = response.trim();
}
return response;

answered Feb 10, 2015 at 3:49

user1302353

1

1 Comment

SkyClasher Over a year ago

if the response is referring to null, what should i do?

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