使用ion-koush在JsonArray.toString（）上的Android null对象引用

Question

im working on a website and android app. im using the koush/ion library im now struggling with this problem wherein the json is null, i have confirmed this with

System.out.print(result);

i am currently testing this code out to learn how jsonobject and jsonarray works in android. i am a beginner in json. im also trying to insert the jsonarray into my table view

this is the android activity

public class TestActivity extends AppCompatActivity {

TableLayout usertabletest;
static JSONArray arr = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.test);

    usertabletest = (TableLayout) findViewById(R.id.usertabletest);

    View tablehead = LayoutInflater.from(this).inflate(R.layout.testlol, null, false);
    TextView idhead = (TextView) tablehead.findViewById(R.id.idtest);
    TextView useridhead = (TextView) tablehead.findViewById(R.id.useridtest);
    TextView passwordhead = (TextView) tablehead.findViewById(R.id.passwordtest);
    TextView rolehead = (TextView) tablehead.findViewById(R.id.roletest);

    idhead.setText("id");
    useridhead.setText("userid");
    passwordhead.setText("password");
    rolehead.setText("role");

    usertabletest.addView(tablehead);

    Ion.with(this)
            .load("http://267.site11.com/doubletime-app/sql.php")
            .asJsonArray()
            .setCallback(new FutureCallback<JsonArray>() {
                @Override
                public void onCompleted(Exception e, JsonArray result) {
                    try {
                        JSONArray arr = new JSONObject(result.toString()).getJSONArray("posts");
                        // get the 'posts' section from the JSON string
                        for (int i = 0; i < arr.length(); i++) {
                            JSONObject post = arr.getJSONObject(i).getJSONObject("post");
                            String id = post.getString("id");
                            String userid = post.getString("userid");
                            String password = post.getString("password");
                            String role = post.getString("role");

                            buildtable(id, userid, password, role);
                        }
                    } catch (JSONException E) {
                        E.printStackTrace();
                    }
                }
            });
}

and this is my sql.php

<?php
    include 'JSON.php';
    $query = "SELECT * FROM user_accounts";
    encodequery($query);
?>

this is JSON.php

<?php
function encodequery($query) {
$dbhost = "localhost";
$dbuser = "id1341573_267admin";
$db = "id1341573_rotc";
$dbpass = "iloveyou267";

$conn = new mysqli($dbhost, $dbuser, $dbpass,$db) or die("Connect failed: %s
". $conn -> error);

$result = mysqli_query($conn, $query) or die(mysqli_error($conn));

$posts = array();

if(mysqli_fetch_array($result)) {
  while($post = mysqli_fetch_assoc($result)) {
     $posts[] = array('post'=>$post);
     }
   }
encodearray($posts);
}

function encodearray($posts) {
header('Content-type: application/json');
echo json_encode(array('posts'=>$posts));
}

?>

Answer 1

Try this

The difference between [ and { – (Square brackets and Curly brackets)

If your JSON node starts with [, then we should use getJSONArray() method. Same as if the node starts with {, then we should use getJSONObject() method.

Ion.with(context)
            .load(url)
            .asJsonObject()
            .setCallback(new FutureCallback<JsonObject>() {
                @Override
                public void onCompleted(Exception e, JsonObject result) {
                    // TODO
                   try 
                   {
                      JSONArray arr  = result.getJSONArray("posts");

                      for (int i = 0; i < arr.length(); i++)
                      {
                         JSONObject post = arr.getJSONObject(i).getJSONObject("post");
                         String id = post.getString("id");
                         String userid = post.getString("userid");
                         String password = post.getString("password");
                         String role = post.getString("role");
                         String syncsts = post.getString("syncsts");

                         Log.i("ID "," "+id);
                         Log.i("User id "," "+userid);
                         Log.i("Password "," "+password);
                         Log.i("Role "," "+role);
                         Log.i("Syncsts "," "+syncsts);

                         buildtable(id, userid, password, role);
                     }
                } catch (JSONException E) {
                    E.printStackTrace();
                }
                }
            });