使用 PHP 将 JSON 数组发送到 Android Volley

Question

I am sending an array of data from MySQL query, and I am using json_encode to do that:

public function getFriends($id){
$query = mysql_query(" SELECT uid, name, email
                        FROM users
                        RIGHT JOIN friendships 
                        ON friendid2 = uid")        or die (mysql_error());

$jsonData = '{"tag":"friends",error":"false",';
$jsonData .= '"friends":[';

while($row = mysql_fetch_array($query)){
    $i++;
    $id = $row["uid"];
    $name = $row["name"];
    $email = $row["email"];
    $jsonData .= '{"id":"'.$id.'","name":"'.$name.'","email":"'.$email.'"},';
}

$jsonData = chop($jsonData, ",");
$jsonData .= ']}';
echo json_encode($jsonData);

In the Android LogCat, when I'm creating JSON object I see this:

 org.json.JSONException: Value {"tag":"friends",error":"false","friends":[{"id":"4","name":"GrubyJohny2","email":"gruby@gmail.com"},{"id":"243000000","name":"Wariacik","email":"karol@wp.com"}]} of type java.lang.String cannot be converted to JSONObject

Can anyone tell me what am I doing wrong ? Becouse I searched bounch of toutorials and I think my json syntax is correct.

The way I am receiving message from server:

private void getFriendships(final String id) {

    String tag_string_req = "req_friendships";
    pDialog.setMessage("Sending Request for list of friends");
    showDialog();
    final String TAG = "List of friends request";
    StringRequest strReq = new StringRequest(Request.Method.POST, AppConfig.URL_REGISTER, new Response.Listener<String>() {

        @Override
        public void onResponse(String response) {
            Log.d(TAG, "Friendship request Response: " + response.toString());
            hideDialog();
            try {

                JSONObject jObj = new JSONObject(response); 
                boolean error = jObj.getBoolean("error");

                if (!error) {

                    Toast.makeText(getApplicationContext(), "Friends uploaded", Toast.LENGTH_LONG).show();

                } else {

                    String errorMsg = jObj.getString("error_msg");
                    Toast.makeText(getApplicationContext(), errorMsg, Toast.LENGTH_LONG).show();
                }
            } catch (JSONException e) {
                Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e(TAG, "List of friends request Error: " + error.toString());

            Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG).show();
            hideDialog();

        }
    }) {

        @Override
        protected Map<String, String> getParams() {
            Map<String, String> params = new HashMap<String, String>();
            params.put("tag", "friends");
            params.put("sender", id);

            return params;
        }

    };

    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}

Answer 1

"friends",error":"false"

The error key needs quotes on both sides.

You can copy / paste the JSON in many free services, such as jsonlint.org that will parse your string for you and tell you if and where the errors are.

As @Noman pointed out in the comments, you can also just build out the entirety of the data as a PHP array (and not just portions of it), and then simply json_encode all of it at the very end:

$jsonData = array(
    'tag' => 'friends',
    'error' => 'false',
    'friends' => array(),
);

while($row = mysql_fetch_array($query)) {
    $jsonData['friends'][] = array(
        'id'    => $row['uid'],
        'name'  => $row['name'],
        'email' => $row['email'],
    );
}

echo json_encode($jsonData);

Also, it should be noted that mysql_query as well as all mysql_* functions are now deprecated . You should not write new code that uses these functions. Instead you should learn to use either PDO or mysqli extensions for communicating with your database.