Я пытаюсь получить данные из базы данных MySql. Это код php:
<?php if($_SERVER["REQUEST_METHOD"]=="POST"){ include 'connection.php'; showStudent(); } function showStudent(){ global $connect; $query = " Select * FROM utenti"; $result = mysqli_query($connect, $query); $number_of_rows = mysqli_num_rows($result); $temp_array = array(); if($number_of_rows > 0) { while ($row = mysqli_fetch_assoc($result)) { $temp_array[] = $row; } } header('Content-Type: application/json'); echo json_encode(array("utenti"=>$temp_array)); mysqli_close($connect); } ?> И это метод получения данных:
public static String mostraDati(){ final String[] result = new String[50]; System.out.println("ww"); JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, DatiNet.MostraDati, new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { System.out.println("fin qui ci siamo"); try { JSONArray utenti = response.getJSONArray("utenti"); for (int i = 0; i < utenti.length(); i++) { JSONObject student = utenti.getJSONObject(i); String nome = student.getString("nome"); String cognome = student.getString("cognome"); String numero = student.getString("numero"); String email = student.getString("email"); result[i] = nome + " " + cognome + " " + email + "\n"; } } catch (JSONException e) { e.printStackTrace(); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { System.out.append(error.getMessage()); } }); requestQueue.add(jsonObjectRequest); return result[0]; }
Когда я выполняю их, приложение падает.
Это журнал:
10-10 19:45:26.363 4373-4373/com.rete.prova.ale.reteale E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.rete.prova.ale.reteale, PID: 4373 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rete.prova.ale.reteale/com.rete.prova.ale.reteale.MostraDati}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.Request com.android.volley.RequestQueue.add(com.android.volley.Request)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.Request com.android.volley.RequestQueue.add(com.android.volley.Request)' on a null object reference at com.rete.prova.ale.reteale.Rete.mostraDati(Rete.java:98) at com.rete.prova.ale.reteale.MostraDati.onCreate(MostraDati.java:20) at android.app.Activity.performCreate(Activity.java:6237) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
В чем проблема? Я объявила результат окончательным, потому что редактор заставил меня, но константу нельзя изменить правильно?
Попробуй это:
private static List<String> result = new ArrayList<String>(); public static void mostraDati(){ System.out.println("ww"); JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, DatiNet.MostraDati, new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { System.out.println("fin qui ci siamo"); try { JSONArray utenti = response.getJSONArray("utenti"); for (int i = 0; i < utenti.length(); i++) { JSONObject student = utenti.getJSONObject(i); String nome = student.getString("nome"); String cognome = student.getString("cognome"); String numero = student.getString("numero"); String email = student.getString("email"); result.add(nome + " " + cognome + " " + email); // or use StringBuilder to create string! } } catch (JSONException e) { e.printStackTrace(); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { System.out.append(error.getMessage()); } }); }
для показа данных используйте это:
for(String s : result) { System.out.println(s); }
попробуйте этот запрос php:
<?php mysql_connect("localhost","root","password"); mysql_select_db("DBName"); $q=mysql_query("SELECT * FROM utenti"); while($e=mysql_fetch_assoc($q)) $output[]=$e; print(json_encode($output)); mysql_close(); ?>в<?php mysql_connect("localhost","root","password"); mysql_select_db("DBName"); $q=mysql_query("SELECT * FROM utenti"); while($e=mysql_fetch_assoc($q)) $output[]=$e; print(json_encode($output)); mysql_close(); ?>