从Android获取带有StringRequest的JSONArray

Question

I am trying to get hold of a JSONArray by using StringRequest in Android along with the POST-method.

The php-script is written like:

$statement = mysqli_prepare($con, "SELECT * FROM tickets WHERE user_id > 5 AND completed = 1");
    mysqli_stmt_bind_param($statement, "i", $UID);
    mysqli_stmt_execute($statement);

    mysqli_stmt_store_result($statement);
    mysqli_stmt_bind_result($statement, $user_id, $beacon_id, $timeFrom, $timeTo, $completed);



    $jsonObject = array();
    $response = array();

    while($status = mysqli_stmt_fetch($statement)){
            $jsonObject = null;

            $jsonObject["beacon_id"]= $beacon_id;
            $jsonObject["timeFrom"]= $timeFrom;
            $jsonObject["timeTo"]= $timeTo;

            $response[] = $jsonObject;
    }

echo json_encode($response);?>

Accessing the web-page with the php-script, the following JSONArray is "echoed":

[{"beacon_id":10,"timeFrom":"2018-02-14 13:07:11","timeTo":"2018-02-14 14:32:53"},{"beacon_id":3,"timeFrom":"2018-02-24 13:33:37","timeTo":"2018-02-24 13:33:47"}]

And as I understand this is a normal JSONArray with square-brackets representing the array and curly-brackets for each JSONObject inside the array.

When I try to access this JSONArray through a StringRequest in Android Studio (Java), I do not get any results...

The StringRequest code:

public class HistoryRequest extends StringRequest {
    private static final String HISTORY_REQUEST_URL = "http://myURL.../myPHPfile.php";
    private Map<String, String> params;

    public HistoryRequest(String user_id, String instanceID, Response.Listener<String> listener) {
        super(Method.POST, HISTORY_REQUEST_URL, listener, null);
        params = new HashMap<>();
        params.put("user_id", user_id);
        params.put("instanceID", instanceID);
}

    @Override
    public Map<String, String> getParams() {return params;}
}

The ResponseListener in the MainActivity is written like:

Response.Listener<String> responseListener = new Response.Listener<String>() {
@Override
public void onResponse(String response) {
    JSONArray jsonArray = new JSONArray(response);
    for(int i = 0; i < jsonArray.length(); i++) {
        JSONObject jsonObject = jsonArray.getJSONObject(i);

        String timeFrom = jsonObject.getString("timeFrom");
        String timeTo = jsonObject.getString("timeTo");

        textviewFrom.append(timeFrom);
        textviewTo.append(timeTo);
        }
    }
};

Any tips why I can't make a JSONArray of the String that in the web-page URL looks like a beautiful JSONArray?

Thanks in advance!

UPDATE:

After switching to JSONArrayRequest instead of StringRequest, I can get the data if I change the MySQL part of the php-script to something static like:

SELECT * FROM tickets;

Then I can display all the entries. But I tend to send 1 parameter to the server (user_id), so that I can filter the entries based on the user that is logged in. [SELECT * FROM tickets where user_id = ?], like a traditional POST-method....

Someone who knows what to do? Read several places that you can not @Override the getParams()-method for this...

SOLVED:

I solved the issue by entering the keyvalue (user_id) into the URL.

//Instead of POST:
$user_id = $_POST["user_id"];

// I use SERVER to get the value after ? in the URL:
$user_id = $_SERVER['QUERY_STRING'];

Doing this with the following java-code:

public class HistoryRequest extends JsonArrayRequest {
private static final String HISTORY_REQUEST_URL = "http://myURLorIPaddress/getHistory.php?";

    public HistoryRequest(String UID, Response.Listener<JSONArray> listener) throws JSONException {
        super(Method.POST, HISTORY_REQUEST_URL + UID,null, listener, null);
}
}

This made it possible to filter the result based on user_id and works like a charm :D

Answer 1

I do not get to print anything, but I can see that the Volley library is complaining for some external errors (nothing referred to my code). The log.i("OnResponseLog", response) does not provide anything.

Picture of error from LogCat:

Answer 2

I am working in similar project did you check if there are some null entries? I think the problem might be there by checking your LogCat picture.

Check using isNull() function might be good idea. https://processing.org/reference/JSONObject_isNull_.html