如何在Android中检索json数组？

Question

Below is my Android code which is supposed to retrieve the json array. But it shows an exception that "json array cannot be converted to json object". What is wrong with this code?

JSONObject json = new JSONObject(result);
JSONArray jArray = json.getJSONArray("emparray");

ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

// testing works ...

// ... until here
for (int i = 0; i < jArray.length(); i++) {
    json = jArray.getJSONObject(i);

    String id = null, loc = null;
    id = json.getString("user_id");

    loc = json.getString("crtloc_lat");

    HashMap<String,String> persons2 = new HashMap<String,String>();
    persons2.put("uder_id",id);
    persons2.put("crtloc_lat",loc);
    personList.add(persons2);
    mylist.add(persons2);
    Toast.makeText(MapsActivity.this, "waw id is"+id, Toast.LENGTH_SHORT).show();
}

PHP file

 <?php
require "config.php";
$con = mysqli_connect(HOST,USER,PASS,DB);

$pro_id=2;
$sql="SELECT user.user_id, current_location.crtloc_lat,current_location.crtloc_lng FROM user INNER JOIN current_location 
where user.user_id=current_location.user_id AND user.pro_id='$pro_id'";



  $result = mysqli_query($con, $sql) or die("Error in Selecting " . mysqli_error($con));

    //create an array
    $emparray[] = array();
    while($row =mysqli_fetch_assoc($result))
    {
        $emparray[] = $row;
    }
    echo json_encode($emparray);

    //close the db connection
    mysqli_close($con);
?>

and the following is my json array

[[],{"user_id":"77","crtloc_lat":"34.769638","crtloc_lng":"72.361145"},{"user_id":"76","crtloc_lat":"34.769547","crtloc_lng":"72.361504"},{"user_id":"87","crtloc_lat":"33.697117","crtloc_lng":"72.976631"},{"user_id":"86","crtloc_lat":"33.697117","crtloc_lng":"72.976631"}]

Answer 1

You should check your JSON as string to understand where is the problem, in any case if result is a JSON Array (like [ .... ] ) your first line is wrong

JSONObject json = new JSONObject(result);
JSONArray jArray = json.getJSONArray("emparray");

It should be

JSONArray jArray = json.getJSONArray(result);

But to be sure you should post your JSON string...

There are also another think that makes me a little bit confused, in JAVA a JSONObject is created around an HashMap (as you can see here ) and a JSONArray is very close to an Array of HashMap ...

I think that what are you tring to do is a bit useless...