Android Volley döndürülemiyor String

Question

Veri tabanından bir liste url'si almak istediğim bir ders ürettim. Bu şimdiye sınıfını kullanıyorum hangi faaliyettir

03-30 15:05:35.599 3591-3591/? E/AndroidRuntime: FATAL EXCEPTION: main 
               Process: com.example.imran.myapp, PID: 3591 
               java.lang.NullPointerException: Attempt to read from null array 
                at com.example.imran.myapp.gridgallery.onCreateView(gridgallery.java:55) 
                at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962) 
                at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1026) 
                at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1207) 
                at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) 
                at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1572) 
                at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:493) 
                at android.os.Handler.handleCallback(Handler.java:739) 
                at android.os.Handler.dispatchMessage(Handler.java:95) 
                at android.os.Looper.loop(Looper.java:145) 
                at android.app.ActivityThread.main(ActivityThread.java:6145) 
                at java.lang.reflect.Method.invoke(Native Method) 
                at java.lang.reflect.Method.invoke(Method.java:372) 
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399) 
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194) 
03-30 15:05:35.599 1032-1045/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp 
03-30 15:05:35.599 1032-1045/? W/ActivityManager: Force finishing activity com.example.imran.myapp/.Home 
03-30 15:05:35.609 1032-1045/? V/ApplicationPolicy: isApplicationStateBlocked userId 0 pkgname com.example.imran.myapp 
03-30 15:05:35.909 1032-1032/? D/CrashAnrDetector: processName: com.example.imran.myapp 
03-30 15:05:35.919 1032-1032/? D/CrashAnrDetector: broadcastEvent : com.example.imran.myapp data_app_crash 
03-30 15:05:36.159 1032-1059/? W/ActivityManager: Activity pause timeout for ActivityRecord{3f2af340 u0 com.example.imran.myapp/.Home t3125 f} 
03-30 15:05:37.019 1032-1521/? I/WindowState: WIN DEATH: Window{224e112b u0 com.example.imran.myapp/com.example.imran.myapp.Home} 
03-30 15:05:37.079 1032-1528/? I/ActivityManager: Process com.example.imran.myapp (pid 3591)(adj 9) has died(67,606) 
03-30 15:05:37.359 10199-10199/? D/AASAservice-UpdateReceiver: AASAUpdateReceiver: android.intent.action.PACKAGE_REPLACED, package = com.example.imran.myapp, uid = -1 
03-30 15:05:37.379 2433-3619/? D/PkgBroadcastIntentOp: Received broadcast action=android.intent.action.PACKAGE_REPLACED and uri=com.example.imran.myapp 
03-30 15:05:37.559 2433-3974/? D/k: Processing package: com.example.imran.myapp 
03-30 15:05:37.559 2227-3976/? D/Compatibility: intentservice saw: Intent { act=android.intent.action.PACKAGE_REPLACED dat=package:com.example.imran.myapp flg=0x4000010 cmp=com.sec.android.app.soundalive/.compatibility.Compatibility$Receiver (has extras) } Bundle[{android.intent.extra.UID=10252, android.intent.extra.REPLACING=true, android.intent.extra.user_handle=0}] 
03-30 15:05:37.589 2433-3974/? D/GassUtils: Found app info for package com.example.imran.myapp:1. Hash: 6b9333e031907d7a6a6c12cd9fdfa0d23bd13ee0f40c9617ddd005dc358321b0 
03-30 15:05:37.589 2433-3974/? D/k: Found info for package com.example.imran.myapp in db. 

: Ama bu hatayı alıyorum AlbumsList.java yılında gridgallery.java

public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.fragment_gridgallery, null); 
    Myserver myserver = new Myserver(); 
    //postStringRequest(myserver.url + "/api/albums/getalbums.php", view); 
AlbumsList albumsList = new AlbumsList(myserver.url+"/api/albums/getalbums.php",getContext(),view); 
albumsList.connection(); // Do connection 
Toast.makeText(getContext(),albumsList.imgsurls[1],Toast.LENGTH_LONG).show(); 
/* 
GridView gv = (GridView)view.findViewById(R.id.fragment_gridgallery); 
ImageAdapter myadapter = new ImageAdapter(getContext(),albumsList.imgurls()); 
gv.setAdapter(myadapter); 
*/ 
return view; 
} 

AlbumsList.java

public class AlbumsList { 
    private String server; 
    Context mycontext; 
    public String[] imgsurls; 
    private View view; 
    AlbumsList(String serverurl, Context c,View uview){ 
     mycontext = c; 
     server = serverurl; 
     view = uview; 
    } 

    public View connection(){ 
     // Instantiate the RequestQueue. 
     RequestQueue queue = Volley.newRequestQueue(mycontext); 
     // Request a string response from the provided URL. 
     StringRequest stringRequest = new StringRequest(Request.Method.POST, server, 
       new Response.Listener<String>() { 
        @Override 
        public void onResponse(String response) { 
         //GridView gv = (GridView)view.findViewById(R.id.fragment_gridgallery); 
         final ArrayList<String> urls2 = new ArrayList<String>(); 
         try { 
          JSONArray jsonObj = new JSONArray(response); 
          Myserver myserver = new Myserver(); 
          for (int i=0;i<jsonObj.length();i++){ 
           JSONObject c = jsonObj.getJSONObject(i); 
           String imgurl = myserver.url+"/images/thumbs/tn_"+c.getString("album_thumbnail"); 
           urls2.add(imgurl); 
          } 
          final String myabc[] = urls2.toArray(new String[urls2.size()]); //Do not remove this 
          imgsurls = myabc; 
          Toast.makeText(mycontext, imgsurls[0], Toast.LENGTH_LONG).show(); //Interestingly this toast works and imgsurls[] is ok 

         } catch (JSONException e) { 
          e.printStackTrace(); 
          Toast.makeText(mycontext,e.getLocalizedMessage(),Toast.LENGTH_LONG).show(); 
         } 

        } 
       }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
       Toast.makeText(mycontext, "Unable to reach server", Toast.LENGTH_LONG).show(); 
      } 
     }) { 
      @Override 
      protected Map<String, String> getParams() { 
       Map<String, String> params = new HashMap<String, String>(); 
       params.put("getalbum", "getalbum"); 
       return params; 
      } 
     }; 
     queue.add(stringRequest); 
     return view; 
    } 

    public String[] imgurls(){ 
     return imgsurls; 
    } 
} 

ben dönmek istiyorum URLS'nin bir işlevi veya değişkenleri tarafından listesi, ancak her iki yaklaşım da çalışmaz. İlginç bir şekilde, URL'ler veritabanından uygun şekilde getirilir. Ve AlbumsList.java: Toast.makeText(mycontext, imgsurls[0], Toast.LENGTH_LONG).show(); içerideki Tost da işe yarıyor. Öyleyse neden imgsurls'un ana fonksiyona dönmediğini bilmiyorum. Şimdiden teşekkürler.

Answer 1

Volley isteği nedeniyle asenkron. Eğer albumsList.connection(); ararken

Böylece, istek arka planda çalışırken ve tamamlanmadan önce, kontrol aşağıdaki satıra gelir:

Toast.makeText(getContext(),albumsList.imgsurls[1],Toast.LENGTH_LONG).show(); 

Ve o zamana kadar

, isteğiniz tamamlanmaz.

Answer 2

Volley, eşzamansız bir şekilde çalışır. Bu, işlemin sonucunu hemen döndürmediği anlamına gelir. Sunucudan alınmadan önce sonuçlara erişmeye çalışıyorsunuz.

Sonuç gerçekten teslim edildiğinde, görünüm başlangıç ​​mantığınızı onResponse() ürününe taşımanız gerekir.