android - スピナーが空です

Question

スピナーに MySQL からのデータを入力しようとしています (行を作成する必要があります) が、空のままです。また、これらのスピナーは相互に依存する必要があります。理由はありますか？ローカル ホストで url を呼び出すと、正しい値が返されるため、PHP は正常に動作しています (PHP からの 1 行の例: [{"Grad":"Beograd","Predmet":"matematika"}...], 私はそれらの行をリストに入れることについてもっと心配しています。

public class IzboraGrada extends Activity {
    Spinner spinner1, spinner2;
    private Button button,izlaz;
    static String str_grad,str_predmet,url;

    InputStream is=null;
    String result=null;
    String line=null;
    String[] grad, predmet;   


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_izbora_grada);

        spinner1=(Spinner) findViewById(R.id.spinner1);
        spinner2=(Spinner) findViewById(R.id.spinner2);

        final List<String> list1=new ArrayList<String>();
        final List<String> list2=new ArrayList<String>();

        Button b=(Button) findViewById(R.id.button);

        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                try
                {
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost("http://192.168.1.14/test/spinner1.php");
                HttpResponse response = httpclient.execute(httppost);
                Log.e("Fail 1", "3");

                HttpEntity entity = response.getEntity();
                Log.e("Fail 1", "4");

                is = entity.getContent();
                Log.e("Pass 1", "connection success ");
                }
                catch(Exception e)
                {
                Log.e("Fail 1", e.toString());
                Toast.makeText(getApplicationContext(), "Invalid IP Address",Toast.LENGTH_LONG).show();
                finish();
                } 

                try
                {
                BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
                StringBuilder sb = new StringBuilder();
                while ((line = reader.readLine()) != null)
                {
                sb.append(line + "\n");
                }
                is.close();
                result = sb.toString();
                }
                catch(Exception e)
                {
                Log.e("Fail 2", e.toString());
                }    

                try
                {
                JSONArray JA=new JSONArray(result);
                JSONObject json= null;
                grad = new String[JA.length()];       
                predmet = new String[JA.length()];

                for(int i=0;i<JA.length();i++)
                {
                json=JA.getJSONObject(i);
                grad[i] = json.getString("Grad");
                predmet[i]=json.getString("Predmet");
                }
                Toast.makeText(getApplicationContext(), "sss",Toast.LENGTH_LONG).show();

                for(int i=0;i<grad.length;i++)
                {
                list1.add(grad[i]);
                list2.add(predmet[i]);
                }

                spinner_fn();

                }
                catch(Exception e)
                {

                Log.e("Fail 3", e.toString());
                //login.this.finish();

                }
            }
        });
    }

    private void spinner_fn() {
        // TODO Auto-generated method stub

        ArrayAdapter<String> dataAdapter1 = new ArrayAdapter<String>(getApplicationContext(),
                                    android.R.layout.simple_spinner_item, grad);
    dataAdapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner1.setAdapter(dataAdapter1);



        ArrayAdapter<String> dataAdapter2 = new ArrayAdapter<String>(getApplicationContext(),
                                    android.R.layout.simple_spinner_item, predmet);
    dataAdapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner2.setAdapter(dataAdapter2);   

        spinner1.setOnItemSelectedListener(new OnItemSelectedListener()
        {
        public void onItemSelected(AdapterView<?> arg0, View arg1,int position, long id)
        {
        // TODO Auto-generated method stub

        spinner2.setSelection(position);

        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0)
        {
        // TODO Auto-generated method stub
        }

        });


        spinner2.setOnItemSelectedListener(new OnItemSelectedListener() {

        public void onItemSelected(AdapterView<?> arg0, View arg1,int position, long arg3) {
        // TODO Auto-generated method stub

        spinner1.setSelection(position);

        }

        public void onNothingSelected(AdapterView<?> arg0) {
        // TODO Auto-generated method stub
        }
        });

        }   
}

そしてPHPコード：

$con = mysqli_connect($host, $user, $pwd, $db);

if(mysqli_connect_errno($con)) {
    die("Failed to connect to MySQL: " . mysqli_connect_error());
} 


$sql = "SELECT Grad, Predmet FROM lista";
$result = mysqli_query($con, $sql);

$rows = array();

while($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {

        $rows[] = $row; 

}

mysqli_close($con);

echo json_encode($rows);